Aeroacoustic Analysis of Dipole Noise Patterns in Low Reynolds Number Square Cylinder Flows

Aeroacoustic Analysis of Dipole Noise Patterns in Low Reynolds Number Square Cylinder Flows | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Aeroacoustic Analysis of Dipole Noise Patterns in Low Reynolds Number Square Cylinder Flows Mahesh Nakka, Basanta Kumar Rana, Atal Bihari Harichandan This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5597009/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract This research provides a detailed investigation into the mechanisms of aeroacoustic noise generation linked to square cylinder aerodynamics under low Reynolds number conditions. Utilizing ANSYS Workbench, fluid dynamic and acoustic interactions are analyzed at very low Reynolds numbers (Re = 100 and 200). The study focuses on key parameters driving noise production, such as turbulence, unsteady pressure fluctuations, and the interaction between the square cylinder's surface and the surrounding airflow. Findings reveal a characteristic dipole noise pattern at Re = 100 and Re = 200, with maximum noise levels located at the top and bottom surfaces due to predominant lift fluctuations. Conversely, noise levels are at their minimum within the vortex streets, driven primarily by drag fluctuations. These findings contribute to a broader understanding of the aeroacoustic properties of square cylinders, offering insight into mitigating noise in aerospace, civil engineering, and other noise-critical engineering applications. Aeroacoustic Square Cylinder Reynolds Number Turbulence Dipole Noise Fluid Dynamics Aeroelasticity Noise Control Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 1. Introduction In the realm of fluid dynamics and acoustics, the investigation of flow over bluff bodies has been a significant area of research due tothe complexity and practical applications of a subject enduring fascination and practical importance. One such archetype of bluff bodies is square cylinder, whose sharp edges and flat surfaces elicit complex flow patterns characterized by vortex shedding and intricate wake structures. The interaction between these flow phenomena and the generation of acoustic waves constitutes a multifaceted and challenging problem in aeroacoustics. Understanding the aero acoustic characteristics of flow past a square cylinder holds paramount significance in various engineering applications, ranging from automotive and aerospace industries to design of buildings and civil structures, where mitigating noise generation is essential for improved performance and comfort. In the realm of aeroacoustics, understanding the intricate mechanisms governing noise generation is paramount. The present study delves into the fundamental processes that give rise to aero acoustic noise, focusing on the dynamic interplay of vortex-induced oscillations, shear layer instabilities, and Kelvin-Helmholtz instabilities. These mechanisms play a pivotal role in shaping the acoustic landscape around aerodynamic structures. Vortex-induced oscillations occur when vortices shed from the body of an object interact with the surrounding fluid, creating periodic fluctuations in the flow velocity and pressure. Simultaneously, shear layer instabilities manifest as disturbances at the boundary between different fluid layers, leading to complex flow patterns and pressure variations. Kelvin-Helmholtz instabilities arise due to velocity differences between adjacent fluid layers, generating turbulent eddies that contribute significantly to noise production. By elucidating these mechanisms, our study aims to unravel the underlying physics of aero acoustic noise, shedding light on the intricate dynamics that have a profound impact on various engineering applications, including aircraft design and wind energy systems. Many researchers have conducted extensive inquiries into examining the flow characteristics of both 2D and 3D configurations. These investigations have brought to light critical facets of the flow, such as the identification of recirculation zones, the transfer of the transfer of mass and momentum transfer across shear layers, the creation of vortex patterns, and the ensuing interactions among these flow phenomena. The primary aim of these investigations has been to ascertain the dynamic fluid forces and structural responses, given their fundamental importance across a diverse range of engineering applications. The majority of experimental research has been carried out at higher Reynolds numbers, where the flow predominantly takes on a turbulent nature and exhibits three-dimensional traits. Countless research endeavors have been directed toward this domain, with a primary emphasis on predicting overarching flow phenomena, variations in vertical flow structures, along with the determination coefficientof forces at lower Reynolds numbers. A thorough examination of the existing literature underscores the substantial prospects for delving deeper into the intricate aspects of this flow field is mainly because of the intrinsic complexity of the flow physics involved. Perry et al. [ 1 ] conducted an extensive investigation into the flow characteristics downstream of a circular cylinder using various techniques for visualizing the flow. Their discoveries provided fresh insights into the phenomenon of vortex shedding. They employed time-exposure photography to capture the movement of aluminum particles, enabling the capture of a series of instantaneous streamline configurations that revealed the developing fluid flow structures aft the cylinder. Williamson [ 2 ] embarked on a study of the flow characteristics behind two bluff bodies positioned in parallel within a fluid stream. Various methods for visualizing the flow were deployed to scrutinize the flow patterns. It was observed that when the separation between the bodies exceeded a certain critical dimension, a phenomenon known as synchronized vortex shedding occurred. Braza et al.,[ 3 ] delved into turbulent flow characteristics near a a circular cylinder at high Reynolds numbers of 1000, focusing on an extended physical time span. They utilized a numerical approach based on velocity formulation and conservative schemes, ensuring second-order accuracy. Vortex shedding was initiated through a numerical perturbation applied for a brief period. Zhou et al. [ 4 ] carried outan experimental research to analyze the attributes of turbulent wakes produced by placing 2 and 3 cylinders side-to-side. The term "complex wake" denotes the flow structure formed resulting from the interaction of multiple wakes created by adjacent cylinders. Bhattacharyya and Maiti [ 5 ] conducted an numerical investigation to analyze the flow characteristics around an square cylinder positioned near the moving wall. Their study aimed to investigate the influence of varying gap heights between the cylinder and the wall, as well as different Reynolds numbers, on flow characteristics. Sharma and Eswaran [ 6 ] conducted a numerical investigation on fluid flow patterns and heat transfer properties of a square cylinder subjected to cross-flow. They examined flow scenarios under both unconfined and channel-confined scenarios, considering blockage ratios which are ranging from 10–50% in 10% increments, and assessed their impact on the initiation of vortex shedding and its subsequent behavior at Reynolds numbers50, 100, as well as 150, with a Prandtl-Number of 0.7. Roy and Bandyopadhyay [ 7 ] developed a specialized solver tailored for accurately simulating unbounded flow around arbitrary two-dimensional (2D) shapes using the incompressible Navier-Stokes equations. They employed a curvilinear body-fitted collocated grid for precise flow simulation and introduced a novel scheme called Consistent Flux Reconstruction (CFR) for solving unconfined flow scenarios involving square cylinder. Das et al., [ 8 ] investigated flow at low Reynolds numbers around a square cylinder adjacent to the planar wall. The aero acoustic examination of flow around a circular cylinder holds significant importance within the fields of fluid dynamics and acoustics. When flow interacts with a circular cylinder, it often induces unsteady flow phenomena, resulting in the substantial generation of aerodynamic noise. Understanding and mitigating this noise generation process is imperative across various engineering applications, encompassing transportation, aerospace, and renewable energy systems. King and Pfizenmaier [ 9 ] explored the emission of sound from rigid cylinders placed perpendicularly within a uniform flow within a wind tunnel equipped with an anechoic chamber, capable of accommodating a range of Mach numbers. These cylinders exhibited diverse cross-sectional shapes, including Circular, square, rectangular, elliptical, and circular configurations featuring lateral ribs or textured surfaces. In 2014, Weinmann and colleagues [ 10 ] conducted a study exploring a new approach, which is modified Flow-Simulation-Methodology (FSM), to predict flow dynamics and noise generation in the NASA Tandem Cylinder Test. This method combined RANS/LES techniques and involved adjusting turbulent viscosity and the dissipation rate of kinetic energy using damping function. Meanwhile, in 2016, Samion and his team [ 11 ] investigated the impact of inserting a wedge behind a square cylinder at Reynolds number22,000. They examined how this wedge influenced both aerodynamic noise and the flow patterns.Dawi and Akkermans [ 12 ] conducted a comparative analysis of two distinct methods for computing the far-field acoustic emissions produced by 2 square cylinders arranged in tandem. Their experimental results revealed the existence of aeolian tones and broadband noise. Kusano et al. [ 13 ] showcased the effectiveness a numerical approach utilizing the lattice Boltzmann method (LBM) with a grid that resolves the wall for predicting broadband noise produced by turbulent boundary layers at very low Mach numbers(M). Mousavi and Kamali [ 14 ] carried out an investigation to assess the aerodynamic properties of flow over a cylinder with dimensions, employing both experimental and numerical methodologies. The experimental trials took place within a wind tunnel under varying operational conditions, while the numerical study utilized an in-house Open Foam multiphase-acoustic solver. Liu et al. [ 15 ] propose a control strategy for managing cylinder flow in subcritical flow regime (Re = 1.4×105) using a porous material plate attached to an afterbody. This study encompasses three-dimensional numerical simulations that integrate Large-Eddy-Simulation (LES) with the Ffowcs-Williams-Hawkings (FW-H) acoustic analogy. In Roslan et al., [ 16 ] investigated aerodynamic performance of the cylinder-to-flat-plate model for UAVs, and finds that increasing the rotational speed to 1000–1000 rpm clockwise drives the lift coefficient higher, resulting in lower drag. Numerical analysis is performed using ANSYS Fluent 20, with stall-angle delays up to 100. The analysis determines the optimal conditions for the model, and helps to analyze the effects of rotational motion and angle of attack on UAV aerodynamics This research paper embarks on an exhaustive exploration of the aero-acoustic aspects surrounding the numerical simulation of low Reynolds number (100 and 200) flow around a square cylinder. Authors delve deep into the intricacies of mechanisms generating flow-induced noise, shedding light on the vortex shedding phenomenon, its reliance on critical factors like Reynolds number and cylinder geometry, and the subsequent acoustic radiation. Our endeavor seeks not only to enhance our fundamental understanding of these phenomena but also to provide valuable insights for the development of noise reduction strategies and innovative engineering solutions across various domains.InChen [ 17 ] studies investigating supersonic reactive cylinder flow using DSMC reveal the role of molecular energy transfer in pre-shock temperature uncertainties and chemical reactions reducing wall heat flux uncertainty The paper introduces SAUQ principles to DSMC simulations, integrating probabilistic collocation for uncertainty modeling Chem with responses extends previous analyzes and increases economic uncertainty. Ntantis et al. [ 18 ] first sinusoidal tubercles in the NACA 2421 airfoil increased lift by 5.42% at stall AOA, while reducing the decrease in lift coefficient after stall Furthermore, the tubercles contributed to the reduction of sound energy levels, and showed their ability to provide flight without fast performance improves. In the pursuit of enhancing the comprehensiveness and depth of this study, several avenues for improvement and further exploration emerge. Firstly, incorporating advanced turbulence models, like Large-Eddy-Simulation (LES) or Detached-Eddy-Simulation (DES), offer comprehensive insights into the turbulent flow structures and their impact on aero acoustic phenomena. These models can capture finer turbulent scales, offering a closer representation of real-world conditions. Secondly, extending the Reynolds number range beyond the examined values of 100 and 200 could uncover additional nuances in the flow behavior, shedding light on transitional and turbulent flow regimes. Additionally, exploring different geometrical configurations, like altering the aspect ratio of the square cylinder or introducing surface modifications, can elucidate their influence on noise generation mechanisms. Furthermore, coupling experimental observations with computational simulations, utilizing techniques like Particle-Image-Velocimetry (PIV) or Acoustic-Doppler-Velocimetry (ADV), can provide a comprehensive validation framework, ensuring the accuracy of both numerical predictions and experimental results. Integrating these enhancements into future research endeavors can refine the understanding of aero acoustic noise generation around square cylinders, paving the way for more precise engineering applications. 2. Governing equations and numerical considerations This research concentrates on an actual scenario that involves a 2D flow around an unconfined square cylinder depicted in Fig. 1 . Theequations governing the flow of ‘incompressible’, In two-dimensional viscous fluid dynamics, the governing equations consist of the continuity equation alongside the two momentum equation components. In scenarios where there are no external forces or Heat transfer equations can be formulated in a non-dimensional primitive variable representation as follows: Continuity Equation : $$\:\frac{\partial\:u}{\partial\:x}+\frac{\partial\:v}{\partial\:y}=0$$ 1 Momentum Equations : X-momentum equation: \(\:\frac{\partial\:u}{\partial\:t}+\frac{\partial\:\left({u}^{2}\right)}{\partial\:\text{x}}+\frac{\partial\:\left(\text{u}\text{v}\right)}{\partial\:\text{y}}=\frac{\partial\:p}{\partial\:x}+\frac{1}{Re}\times\:(\frac{{\partial\:}^{2}u}{\partial\:{x}^{2}}+\frac{{\partial\:}^{2}u}{\partial\:{y}^{2}})\) (2) Y-momentum equation: \(\:\frac{\partial\:u}{\partial\:t}+\frac{\partial\:\left(\text{u}\text{v}\right)}{\partial\:\text{x}}+\frac{\partial\:\left({v}^{2}\right)}{\partial\:\text{y}}=\frac{\partial\:p}{\partial\:y}+\frac{1}{Re}\times\:(\frac{{\partial\:}^{2}v}{\partial\:{x}^{2}}+\frac{{\partial\:}^{2}v}{\partial\:{y}^{2}})\) (3) In this context, the velocity components u and v correspond to motion in the x and y directions, respectively, with p representing the pressure to the density ratio. The parameter Re represents the Reynolds number, and t signifies non-dimensional time.The non-dimensional time, denoted as \(\:\:t={t}_{dimensional}\times\:\frac{\text{U}{\infty\:}}{L}\) , can be described as result of multiplying dimensional time by ratio of free-stream velocity to characteristic length scale inherent to flow problem. The flow is induced by a 2D uniform flow passing over a square cylinder with no inclination. The variable U ∞ represents the velocity of uniform free-stream fluid flow. The initial conditions for numerical computations involve the free-stream pressure along withvelocity, indicating the abrupt introduction of body into main flow. Continuity or Neumann boundary conditions are enforced at the outlet boundary, while Dirichlet boundary conditions are set at the other boundaries within a rectangular domain. However, a no-slip condition is imposed on surface of the cylinder. Numerical Methods and Simulation Details : In In the pursuit of unraveling the complexities of aeroacoustic noise generation, employing accurate numerical methods and simulation techniques is crucial. The present study utilized advanced computational tools to delve into the intricacies of square cylinder aerodynamics. The governing equations for incompressible, viscous fluid flow were discretized utilizing a finite volume approach, enabling the simulation of 2D flow over an unconfined square cylinder. The numerical simulations were conducted using ANSYS Workbench, a robust platform renowned for its precision in fluid dynamics analyses. An unstructured grid comprising 24,342 triangular cells and 12,125 nodes was employed to capture the intricate flow patterns. To ensure the reliability of our findings, a grid independence analysis was meticulously performed, validating the chosen grid configuration. The simulations involved a detailed examination of flow characteristics at very low Reynolds numbers 100 and 200, providing valuable insights into the aeroacoustic signatures specific to square cylinders. These simulations were performed on high-performance computing clusters, enabling us to obtain accurate and reliable data for further analysis. In tandem with the rigorous numerical simulations, an elaborate experimental setup was devised to validate and augment the findings of the aero acoustic analysis. The experimental configuration involved a precisely engineered unconfined square cylinder placed within a controlled wind tunnel environment. The square cylinder, fabricated from a material ensuring minimal acoustic interference, was subjected to varying flow velocities corresponding to Reynolds numbers of interest (Re = 100 and 200). Careful instrumentation and data acquisition systems were employed to capture the aerodynamic forces and acoustic signals generated during the flow interaction with the square cylinder. The experimental parameters included flow velocity, cylinder dimensions, and microphone placements strategically positioned to record sound pressure levels at specific locations around the cylinder. The gathered experimental data were meticulously compared with the numerical results, enhancing the overall reliability of the study and providing a comprehensive understanding of the aero acoustic phenomena associated with square cylinders. 3. Results and discussion ANSYS Workbench is employed to simulate the flow surrounding an unconfined square cylinder with Re of 100 and 200. The simulation is performed on an unstructured grid consisting of 24,342 triangular cells and 12,125 nodes. To perform numerical calculations, a rectangular domain is chosen, which includes an inlet boundary, an outlet boundary and, upper and lower boundaries positioned at spacings of 10D, 30D, and 15D, from the centre of square cylinder. Figure 2 displays a zoomed-in section of triangular cells surrounding the square cylinder. Based on grid independence test performed on square-cylinder at Re of 100, as shown in Table-1, 160 numbers of nodes are considered on cylinder surface. A study of grid independence test was conducted for flow over a square-cylinder with a Re of 100 as shown in Table 1 . After assessing the changes in drag coefficients and the Strouhal number, it was determined that Grid 3 is the most suitable grid for conducting the flow simulations. The decision to use this grid was based on the results obtained from a grid convergence test performed for the flow field surrounding a square cylinder with a Re of 100. It is important to mention that the selected grid also meets the grid convergence index (GCI) criteria recommended by ASME (2008). Table 1 Grid independence analysis at Re = 100. Number of nodes (on cylinder surface) C d (St) 80 (Grid 1: 16,236 cells) 1.44 0.121 120 (Grid 2: 25,172 cells) 1.52 0.125 160 (Grid 3: 29, 816 cells) 1.55 0.128 200 (Grid 4: 37,738 cells) 1.55 0.128 The vorticity contours and streamlines for flow around an unconfined square cylinder with Re of 100 and 200 at a non-dimensional time t = 100 are illustrated in Fig. 3.. It is evident that in both cases, there is a noticeable shedding of vortices from the leading edge of the cylinder. Figure 4 displays the harmonic variation of the C d . To explore the flow's periodic behaviour, we conducted a Fast-Fourier-Transform (FFT) analysis of coefficient of lift data. The frequency spectrum in Fig. 5 allows us to estimate the frequency of vortex shedding, corresponding to dominant frequency in specific spectrum. Table 2 provides a comparative examination of the C d and Stvalues obtained in this study, alongside other numerical and experimental findings reported in the literature. Table 2 Flow characteristics of a square cylinder at Re = 100 and 200 Flow parameters Drag coefficients (Cd) Strouhal number (St) Re = 100 Re = 200 Re = 100 Re = 200 Davis And Moore (1982) 1.64 1.72 - - Okajima (1990) 0.133 0.144 Arnal (1991) 1.410 1.520 0.152 0.156 Suzuki (1993) - - 0.13 0.14 Sohankar (1998) 1.76 1.78 0.142 0.156 Roy and Bandyopadhyay (2006) [ 7 ] 1.533 1.58 0.1243 0.14 Present result 1.58 1.62 0.128 0.147 . The outcomes derived from this investigation show a favorable alignment with the results reported in existing literature. This satisfactory consistency of flow parameters in the scenarioinstils confidence in extending the current aerodynamic inquiry to explore the aero acoustic characteristics of flow over a square cylinder with Re of 100 and 200. The utilization of high-precision physics-based models is imperative for thorough understanding of noise generation mechanisms and for developing practical models to effectively mitigate noise. Coupled with the advancements in high-performance computing, computational fluid dynamics (CFD) is evolving into a precise and cost-effective tool for engineering design. In real-world scenarios such as fans, trailing edges, and airframe noise, aerodynamic noise arises from complex phenomena like turbulent wakes, boundary layers, flow separation, and their interaction between turbulent flow and irregular rigid objects. Furthermore, sound waves undergo multiple reflections from solid surfaces before reaching an observer. In the current numerical study, we simulated the flow over a square cylinder at very low Re, specifically Re = 100 and 200with ANSYS Workbench. Figure 6 illustrates the schematic of sound generation and transmission resulting from flow past over an unconfined square cylinder. Within the domain, we positioned ten receivers strategically: one just ahead of the stagnation point, one at the highest and lowest points of square cylinder, one immediately downstream of the aft stagnation point, and remaining receivers within the von-Karman vortex street. We recorded the sound pressure levels at these key locations to compare noise levels. To conduct aero acoustic analysis of the flow surrounding a circular cylinder, authors employed the solution of the complete N-S equations within the domain encompassing both the sources of sound and the observer(s). Achieving an accurate representation of sound waves necessitates the use of a numerical scheme characterized by minimal dissipation and dispersion. Even though sound waves carry relatively less energy at low Reynolds numbers, in this context, the acoustic stiffness mandates the use of exceedingly small-time steps to adequately resolve both acoustic and aerodynamic phenomena. To ensure minimal impact from far-field boundaries, the computational domain was substantially extended beyond the source region. Specifically, the inlet, upper, and lower boundaries were situated 15D away from the center of the cylinder., while the outlet boundary was positioned 40D away from the center of the cylinder, where D represents cylinder's diameter. For the simulations at hand, a very small-time step of 10 − 5 was selected for the iterative solution process. In the current investigation of aeroacoustics, we utilized the Williams and Hawkings numerical model provided within the ANSYS Workbench platform. This methodology belongs to a category of techniques where turbulent flow in the immediate vicinity is fully resolved using the Navier-Stokes (N-S) equations, while pressure or density data are gathered within an encompassing region that includes all sound sources in the near-field area. This approach effectively addresses the challenge of extending the computational domain to encompass the far-field. Our calculations in this context employed a second-order discretization scheme for accuracy. Analysis of Acoustic Noise Generation Mechanism Figure Authors embarked on an extensive examination of the intricate mechanisms underlying aero acoustic noise generation to acquire a comprehensive understanding of this complex phenomenon within aero acoustic systems. This endeavor involved a thorough review of existing literature and scrutiny of experimental studies, wherein authors critically assessed and compared various theories and models pertaining to noise generation mechanisms. The present investigation primarily homed in on the identification of pivotal factors influencing noise generation, including flow turbulence, fluctuations in unsteady pressure, and the interactions between solid surfaces and the surrounding fluid. Authors placed special emphasis on understanding how these factors contribute to noise emissions across diverse aero acoustic configurations, spanning from aircraft to wind turbines. This chapter lays the essential groundwork for broader research endeavours, potentially guiding the development of more effective noise reduction strategies and enhanced design practices within the realm of aero acoustics. Acoustic noise has always been generated due to few fundamental phenomena like: vortex induced oscillations, shear layer instabilities and Kelvin-Helmholtz instabilities. The generation of acoustic noise arising from Kelvin-Helmholtz instabilities is a captivating and indispensable facet of aero acoustic research. Kelvin-Helmholtz instabilities manifest when there exists a difference in velocity between adjacent fluid layers, resulting in the formation of distinct rolling vortices at the boundary between these layers. These vortices induce periodic fluctuations in pressure, leading to the emission of acoustic waves and the production of noise. The exploration of Kelvin-Helmholtz instabilities and their associated acoustic manifestations holds immense importance in a wide array of engineering applications, encompassing atmospheric flows, oceanic currents, and interactions between fluids and solid boundaries. Gaining insights into and managing the noise generated by these instabilities not only enhances our comprehension of fundamental fluid dynamics but also furnishes valuable insights for the development of noise mitigation techniques and the optimization of engineering designs to create a quieter and more sustainable environment. In this current research, we conducted an aero acoustic investigation focusing on the flow around a square cylinder at low Re. Figure 7 illustrates the computational grid employed in our numerical computations. It's worth noting that grid independence analysis was not done explicitly. Nevertheless, for present simulations, 160 nodes are considered on cylinder's surface, which was established through the grid independence analysisconducted for fluid flow over square cylinder without acoustic model. However, it's important to mention that the domain dimensions chosen for our current study are significantly larger compared to the previous research. To measure the sound pressure level at various positions around the square cylinder, we designated 10 receiver points following the Williams and Hawkings numerical model within ANSYS Workbench. The positions of these receiver points used for acoustic analysis are detailed in Table 2 Table 2 Receiver positions for acoustic analysis. Receiver No. x-coordinate y-coordinate Receiver − 1 -0.0065 0 Receiver – 2 0 0.0065 Receiver – 3 0 -0.0065 Receiver – 4 0.0065 0 Receiver – 5 0.008 0 Receiver – 6 0.009 0 Receiver – 7 0.01 0 Receiver – 8 0.015 0 Receiver – 9 0.008 -0.007 Receiver − 10 0.008 0.007 Figure 7 illustrates the aero acoustic noise generation simulated in the current study, depicting the establishment of a periodic flow pattern downstream of the cylinder. Vorticity and pressure contours resulting from the numerical simulations of flow over the cylinder at Re of 100 and 200 are presented in Fig. 3. These results confirm the periodic shedding of vortices forming from both the upper and lower surfaces of the cylinder, creating a vortex street downstream. The pressure coefficient and the location of flow separation on the rear side of square cylinder exhibit similar variations, attributed to strong connection between flow separation and the extent of positive pressure gradient (∂P/∂x > 0) upstream of the cylinder, which accelerates the flow. A larger area with a positive pressure gradient, resulting in a lower minimum pressure, delays the separation of the flow. At low Re, the pressure coefficient and flow separation point maintain nearly constant values. The alternating shedding of vortices from the topas well asbottom regions of the square cylinder results in a harmonic pattern in the behaviour of the C l and C d . The C l exhibits a zero mean value at both Re, with fluctuations around this mean more pronounced at the higher Re. Additionally, the frequency of vortex shedding is observed to be higher at the elevated Reynolds number. Following the aerodynamic analysis of flow over the square cylinder, time-dependent of fluid flow solutions are inputted into the Williams and Hawkings numerical model was utilized to predict far-field noise. The frequency spectrum of acoustic noise pressure is then obtained using the First Fourier Transform (FFT) method at 10 far-field receiver points. Figure 8 displays the spectrum of sound pressure levels acquired at Re = 100. It is observed that as vortices detach and shed from the cylinder, they create fluctuations in the pressure field within the wake region. These pressure fluctuations give rise to emission of sound waves into the surrounding medium, resulting in tonal components within the noise spectrum. As illustrated, the noise pattern predicted for the flow at Re = 100 exhibits a dipole pattern, with the highest values occurring at θ = 0° (front stagnation point), 90° (upper surface), and 270° (lower surface). These maxima are primarily influenced by fluctuations in lift, while the minimum values are situated within the vortex street and are influenced by drag fluctuations. The discrepancies between maxima and minima typically range around 11 dB.at Re = 100, with a relatively lower noise level observed at θ = 180° (rear stagnation point). Figure 9 illustrates the spectrum of sound pressure levels resulting from the flow over the square cylinder at Reof 200. The boundary layer separation from the square cylinder's surface gives rise to formation of a shear layer. Instabilities within this shear layer can lead to fluctuations in flow velocity and pressure, consequently generating broadband noise. As the separated flow downstream of the cylinder mixes with the surrounding flow, turbulent interactions occur. The abrupt alterations in flow direction and the turbulent nature of this mixing process contribute to the generation of broadband noise. In this case as well, a dipole noise pattern is predicted for the flow at Re = 200, with the highest values occurring at θ = 90° and 270°, primarily influenced by lift fluctuations, while the minimum value is located within the vortex street, determined by drag fluctuations. At Re 200, the differences to the maximum and minimum values are typically around 55 dB, with a comparatively lower noise level observed at θ of 0° and 180° Moreover, it has come to our attention that the frequency spectrum of sound pressure levels in the Re = 200 case features numerous minor peaks, unlike the Re = 100 case, which exhibits a smoother pattern. This difference can be ascribed to the characteristics of the flow over the square cylinder at Reynolds number 200, where a three-dimensional effect becomes apparent in the flow dynamics. Addressing acoustic noise is a matter of utmost importance to tackle the escalating problem of environmental noise pollution. Excessive noise can have profound adverse impacts on human well-being, leading to stress, sleep disturbances, and a range of physical and psychological ailments. Furthermore, noise pollution can disrupt wildlife, interfering with their communication, feeding behaviours, and overall health. With the ongoing expansion of urban and industrial areas, noise pollution is intensifying. By implementing effective measures to mitigate noise, we can create quieter living environments, improve public health, and safeguard the natural acoustic surroundings for both humans and wildlife. It is essential to prioritize research, policies, and technological advancements aimed at reducing noise levels, ensuring a healthier, more sustainable, and harmonious coexistence with our environment. This can be achieved through the use of various flow control devices such as vortex generators, splitter plates, or porous surfaces, as well as techniques like boundary layer control involving suction or blowing to influence flow and noise characteristics. Additionally, modifying the cylinder's shape to minimize flow separation and vortices can contribute to lowering noise levels. Acknowledging the complexity of aero acoustic simulations and experimental setups, It is crucial to acknowledge the inherent limitations and potential sources of error in the conducted study. One of the primary limitations stems from the assumptions made in the numerical model, which might not fully encapsulate all the intricacies of real-world aerodynamic scenarios. Additionally, uncertainties in the boundary conditions, turbulence models, and discretization schemes could introduce discrepancies between the simulated and actual results. Furthermore, the experimental setup, while meticulously designed, may be susceptible to environmental factors, calibration errors, and sensor inaccuracies. Variability in manufacturing tolerances of the square cylinder could also influence the results. Moreover, the study focused on specific Reynolds numbers Re = 100 and 200 and may not capture the entire spectrum of aero acoustic behaviour at different flow conditions. It is crucial for readers to recognize these limitations to interpret the findings within the defined scope of the study accurately. 4. Conclusions The aerodynamics of flow past circular cylinder and the aero-acoustic noise sources are correlated. The specific noise characteristics and dominant sources can vary depending on factors such as flow velocity, Reynolds number, cylinder diameter, and the presence of flow control devices. Aero acoustic noise mechanisms has been entrailed in terms of vertex induced instability, shear layer instability and Kelvin-Helmholtz instability. The detachment of the boundary layer from the square cylinder surface results in the generation of a shear layer. Instabilities in this shear layer can cause fluctuations in the flow velocity and pressure, resulting in broadband noise generation. The separated flow in the downstream of the cylinder results to turbulent mixing with the surrounding flow. The abrupt changes in flow direction and the turbulent nature of the mixing process contribute to the generation of broadband noise... Declarations Author Contribution [Author 1’s N MAHESH]: Conceptualization, methodology design, computational modeling, and manuscript preparation.[Author 2’s RANA]: Data analysis, validation of results, and visualization of findings.Supervision, project administration, and critical revision of the manuscript for intellectual content.[Author 3’s ATAL BIHARI HARI CHANDAN]: Literature review, interpretation of aeroacoustic phenomena, and drafting of specific sections of the manuscript, Supervision, project administration, and critical revision of the manuscript for intellectual content. References Perry A.E., Chong M.S., & Lim T.T. (1982). The vortex-shedding process behind two-dimensional bluff bodies. J. Fluid Mech., Vol. 116, pp. 70–90. Williamson C.H.K. (1985). Evolution of a single wake behind a pair of bluff bodies. J. of Fluid Mech., Vol. 159, pp. 1–18. Braza M., Chassaing P., & Ha Minh H. (1986). Numerical study and physical analysis of the pressure and velocity fields in the near wake of a circular cylinder. J. Fluid Mech., Vol. 163, pp. 79–130. Zhou Y., So R.M.C., Liu M.H., & Zhang H.J. (2000). Complex turbulent wakes generated by two and three side-by-side cylinders. Int. J. of Heat and Fluid Flow, Vol. 21, pp. 125–133. Bhattacharyya S.,&Maiti D.K. (2004). Shear flow past a square cylinder near a wall. Int. J. of Engg. Science, Vol. 42, pp. 2119–2134. Sharma A.,&Eswaran V. (2005). Effect of channel confinement on the two-dimensional laminar flow and heat transfer across a square cylinder. Num. Heat Transfer, Part A, Vol. 47, pp. 79–107. Roy A.,&Bandyopadhyay G. (2006). A finite volume method for viscous incompressible flows using a consistent flux reconstruction scheme. Int. J. for Numerical Methods in Fluids, Vol. 52, pp 297–319. Das, B. N., Ukamanal, M., &Harichandan, A. B. (2022). Low Reynolds Number Flow Past Square Cylinder in the Vicinity of a Plane Wall. INCAS Bulletin, 14(3). King W. F., and Pfizenmaier E. (2009). An experimental study of sound generated by flows around cylinders of different cross-section. J. of Sound and Vibration, Vol. 328 (3), pp. 318–337. Weinmann, M., Sandberg, R. D., &Doolan, C. (2014). Tandem cylinder flow and noise predictions using a hybrid RANS/LES approach. International Journal of Heat and Fluid Flow, 50, 263–278. Samion, S. R. L., Ali, M. S. M., Abu, A., Doolan, C. J., &Porteous, R. Z. Y. (2016). Aerodynamic sound from a square cylinder with a downstream wedge. Aerospace Science and Technology, 53, 85–94. Dawi, A. H., &Akkermans, R. A. (2018). Direct and integral noise computation of two square cylinders in tandem arrangement. Journal of Sound and Vibration, 436, 138–154. Kusano, K., Yamada, K., & Furukawa, M. (2020). Aeroacoustic simulation of broadband sound generated from low-Mach-number flows using a lattice Boltzmann method. Journal of Sound and Vibration, 467, 115044. Mousavi, S. M., &Kamali, R. (2020). Experimental and numerical investigation of a new active control method to suppression of vortex shedding and reduction of sound pressure level of a circular cylinder. Aerospace Science and Technology, 103, 105907. Liu, H., Zhang, S., Chen, R., Zhou, S., & Zhao, Y. (2022). Numerical study on aerodynamic drag and noise of circular cylinders with a porous plate. Aerospace Science and Technology, 123, 107460. Muhammad SyakirImanRoslan, Hidayatullah Mohammad Ali,AzminShakrineMohdRafie. Rotational Speed Analysis on Double Rotating Cylinder for Cylinder to Flat Plate using Numerical Method. Journal of Aeronautics, Astronautics and Aviation, Vol. 55, No. 3S, pp. 495–506 (2023). DOI: https://doi.org/10.6125/JoAAA.202309_55(3S).09 Hao Chen, Bin Zhang, and Hong Liu. Uncertainty Propagation and Quantification in Direct Simulation Monte Carlo Calculations of Hypersonic Reactive Cylinder Flows. Journal of Aeronautics, Astronautics and Aviation, Vol. 52, No. 2, pp. 133–146 (2020). DOI: 10.6125/JoAAA.202006_52(2).01 Efstratios L. Ntantis, Earl Francis, VetrichelvanPugazendi, Joseph George, Ahmed Tarek, Mohammed Emthias, and Syed Rasheed. Study of Sinusoidal Perturbations on the Leading Edge of an Aircraft Wing. Journal of Aeronautics, Astronautics and Aviation, Vol. 53, No. 3, pp. 375–386 (2021). DOI: 10.6125/JoAAA.202109_53(3).04 . Mehta Arnal M.P., Goering D.J., & Humphrey J.A.C. (1991). Vortex shedding from a bluff body on a sliding wall. J. Fluids Eng., Vol. 113, pp. 384–398. Davis R.W., & Moore E.F. (1982). A numerical study of vortex shedding from rectangles. J. Fluid Mech., Vol. 116, pp. 475–506. Okajima A. (1990). Numerical simulation of flow around rectangular cylinders. J. Wind Engg. Ind. Aerodyn, Vol. 33, pp. 171–180. Sohankar A., Norberg C., & Davidson L. (1998). Low Reynolds-number flow around a square cylinder at incidence: study of blockage, onset of vortex shedding and outlet boundary condition, Int. J. Num. Methods in Fluids, Vol. 26, pp. 39–56 Suzuki H., Yoshiaki N., Toshihiko N., Fukutani K., & Suzuki K. (1993). Unsteady flow in a channel obstructed by a square rod (Crisscross motion of vortex), Int. J. Heat Fluid Flow, Vol.14, pp. 2–9. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-5597009","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":397507300,"identity":"08d8a410-1112-4dbc-a2bd-3af9c221ed6b","order_by":0,"name":"Mahesh Nakka","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA6UlEQVRIiWNgGAWjYFACHgYGxgYgzcx88AGIy0e8Fna2ZAMQl414Lfw8ZhIgPkEtuu1nDz78ucMuj5+Zwazya46dDBsD88NHN/BoMTuTl2zMeya5WLKZIe227LZkoMPYjI1z8Gk5kGMmzdjGnLjhMMOx25LbmIFaeNik8Wo5/8b858+2+sT9hxnbiiW31ROh5UaOGQNv2+HEDczMbIwftx0mRssbY2netuOJMw6zMUszbjvOw8ZMyC/ncww//myrTuzvP//x489t1fb87M0PH+PTggKYecAkscpBgPEHKapHwSgYBaNgxAAAjlJGIFq+GfsAAAAASUVORK5CYII=","orcid":"","institution":"KIIT University","correspondingAuthor":true,"prefix":"","firstName":"Mahesh","middleName":"","lastName":"Nakka","suffix":""},{"id":397507301,"identity":"05b8ef74-3da1-4513-9f64-06ed04b2a68b","order_by":1,"name":"Basanta Kumar Rana","email":"","orcid":"","institution":"KIIT University","correspondingAuthor":false,"prefix":"","firstName":"Basanta","middleName":"Kumar","lastName":"Rana","suffix":""},{"id":397507302,"identity":"6f5b840a-4750-4656-bdaa-e7ecef8dfed1","order_by":2,"name":"Atal Bihari Harichandan","email":"","orcid":"","institution":"Centre for UG and PG Studies, BPUT","correspondingAuthor":false,"prefix":"","firstName":"Atal","middleName":"Bihari","lastName":"Harichandan","suffix":""}],"badges":[],"createdAt":"2024-12-07 05:08:16","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5597009/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5597009/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":73233729,"identity":"0f9be594-4038-4830-9944-d97a4666bf99","added_by":"auto","created_at":"2025-01-08 04:26:44","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":36980,"visible":true,"origin":"","legend":"\u003cp\u003eFlow schematic around an unconfined square cylinder\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-5597009/v1/c4401e61875206698ed9de69.png"},{"id":73233733,"identity":"89c84178-7779-4854-a4bb-bbd6273a9ef1","added_by":"auto","created_at":"2025-01-08 04:26:45","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":272241,"visible":true,"origin":"","legend":"\u003cp\u003eZoomed-in triangular mesh around a square-cylinder.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-5597009/v1/b96c14a25f0f641a66467d6c.png"},{"id":73235081,"identity":"7932bde9-fe3b-4caf-90ed-dfd87c7ffaad","added_by":"auto","created_at":"2025-01-08 04:42:45","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":192064,"visible":true,"origin":"","legend":"\u003cp\u003eVorticity contours and streamlines of flow past a square cylinder.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-5597009/v1/0b59f49eac2dbee3b2255b59.png"},{"id":73233731,"identity":"a294f45f-3eb1-471a-b389-51b4ae8c9dde","added_by":"auto","created_at":"2025-01-08 04:26:45","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":132631,"visible":true,"origin":"","legend":"\u003cp\u003eVariation of C\u003csub\u003ed\u003c/sub\u003e for flow around square cylinder\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-5597009/v1/13ba729711ac5226acff5dd1.png"},{"id":73233740,"identity":"e21d5da3-b532-45d2-9655-ae024051903b","added_by":"auto","created_at":"2025-01-08 04:26:45","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":342572,"visible":true,"origin":"","legend":"\u003cp\u003eVortex shedding frequency spectrum for flow around a square cylinder.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-5597009/v1/a005f23d6c217388676479bb.png"},{"id":73233755,"identity":"a997256b-85df-4355-830f-7bba8970f874","added_by":"auto","created_at":"2025-01-08 04:26:45","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":71175,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic of noise generation by fluid flow over square cylinder.\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-5597009/v1/d1395c6aca607489ef53098f.png"},{"id":73233907,"identity":"1d2c12b6-c29f-448a-803e-641b1657fc07","added_by":"auto","created_at":"2025-01-08 04:34:45","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":1206058,"visible":true,"origin":"","legend":"\u003cp\u003eComputational mesh for flow around a square cylinder.\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-5597009/v1/9850937d6e8746b7bdf696aa.png"},{"id":73233738,"identity":"ce338529-726c-433f-b79b-42eee1149ace","added_by":"auto","created_at":"2025-01-08 04:26:45","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":263879,"visible":true,"origin":"","legend":"\u003cp\u003eOverall sound pressure level at \u003cem\u003eRe\u003c/em\u003e = 100.\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-5597009/v1/bd75c693d9c944188d0d96b9.png"},{"id":73233760,"identity":"a505ac15-5bdc-459f-807d-77dfd2329ab8","added_by":"auto","created_at":"2025-01-08 04:26:45","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":306782,"visible":true,"origin":"","legend":"\u003cp\u003eOverall sound pressure level at \u003cem\u003eRe\u003c/em\u003e = 200\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-5597009/v1/436e03893b44cda3a56b795f.png"},{"id":73235358,"identity":"bfb46caa-a411-4502-8652-86a80f62798f","added_by":"auto","created_at":"2025-01-08 04:50:51","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":4016431,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5597009/v1/87bf1fb1-1175-4c5e-8bc2-372c0359eec9.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Aeroacoustic Analysis of Dipole Noise Patterns in Low Reynolds Number Square Cylinder Flows","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eIn the realm of fluid dynamics and acoustics, the investigation of flow over bluff bodies has been a significant area of research due tothe complexity and practical applications of a subject enduring fascination and practical importance. One such archetype of bluff bodies is square cylinder, whose sharp edges and flat surfaces elicit complex flow patterns characterized by vortex shedding and intricate wake structures. The interaction between these flow phenomena and the generation of acoustic waves constitutes a multifaceted and challenging problem in aeroacoustics. Understanding the aero acoustic characteristics of flow past a square cylinder holds paramount significance in various engineering applications, ranging from automotive and aerospace industries to design of buildings and civil structures, where mitigating noise generation is essential for improved performance and comfort.\u003c/p\u003e \u003cp\u003eIn the realm of aeroacoustics, understanding the intricate mechanisms governing noise generation is paramount. The present study delves into the fundamental processes that give rise to aero acoustic noise, focusing on the dynamic interplay of vortex-induced oscillations, shear layer instabilities, and Kelvin-Helmholtz instabilities. These mechanisms play a pivotal role in shaping the acoustic landscape around aerodynamic structures. Vortex-induced oscillations occur when vortices shed from the body of an object interact with the surrounding fluid, creating periodic fluctuations in the flow velocity and pressure. Simultaneously, shear layer instabilities manifest as disturbances at the boundary between different fluid layers, leading to complex flow patterns and pressure variations. Kelvin-Helmholtz instabilities arise due to velocity differences between adjacent fluid layers, generating turbulent eddies that contribute significantly to noise production. By elucidating these mechanisms, our study aims to unravel the underlying physics of aero acoustic noise, shedding light on the intricate dynamics that have a profound impact on various engineering applications, including aircraft design and wind energy systems.\u003c/p\u003e \u003cp\u003eMany researchers have conducted extensive inquiries into examining the flow characteristics of both 2D and 3D configurations. These investigations have brought to light critical facets of the flow, such as the identification of recirculation zones, the transfer of the transfer of mass and momentum transfer across shear layers, the creation of vortex patterns, and the ensuing interactions among these flow phenomena. The primary aim of these investigations has been to ascertain the dynamic fluid forces and structural responses, given their fundamental importance across a diverse range of engineering applications. The majority of experimental research has been carried out at higher Reynolds numbers, where the flow predominantly takes on a turbulent nature and exhibits three-dimensional traits. Countless research endeavors have been directed toward this domain, with a primary emphasis on predicting overarching flow phenomena, variations in vertical flow structures, along with the determination coefficientof forces at lower Reynolds numbers. A thorough examination of the existing literature underscores the substantial prospects for delving deeper into the intricate aspects of this flow field is mainly because of the intrinsic complexity of the flow physics involved.\u003c/p\u003e \u003cp\u003ePerry et al. [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e] conducted an extensive investigation into the flow characteristics downstream of a circular cylinder using various techniques for visualizing the flow. Their discoveries provided fresh insights into the phenomenon of vortex shedding. They employed time-exposure photography to capture the movement of aluminum particles, enabling the capture of a series of instantaneous streamline configurations that revealed the developing fluid flow structures aft the cylinder. Williamson [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e] embarked on a study of the flow characteristics behind two bluff bodies positioned in parallel within a fluid stream. Various methods for visualizing the flow were deployed to scrutinize the flow patterns. It was observed that when the separation between the bodies exceeded a certain critical dimension, a phenomenon known as synchronized vortex shedding occurred. Braza et al.,[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e] delved into turbulent flow characteristics near a a circular cylinder at high Reynolds numbers of 1000, focusing on an extended physical time span. They utilized a numerical approach based on velocity formulation and conservative schemes, ensuring second-order accuracy. Vortex shedding was initiated through a numerical perturbation applied for a brief period. Zhou et al. [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e] carried outan experimental research to analyze the attributes of turbulent wakes produced by placing 2 and 3 cylinders side-to-side. The term \"complex wake\" denotes the flow structure formed resulting from the interaction of multiple wakes created by adjacent cylinders. Bhattacharyya and Maiti [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e] conducted an numerical investigation to analyze the flow characteristics around an square cylinder positioned near the moving wall. Their study aimed to investigate the influence of varying gap heights between the cylinder and the wall, as well as different Reynolds numbers, on flow characteristics. Sharma and Eswaran [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e] conducted a numerical investigation on fluid flow patterns and heat transfer properties of a square cylinder subjected to cross-flow. They examined flow scenarios under both unconfined and channel-confined scenarios, considering blockage ratios which are ranging from 10\u0026ndash;50% in 10% increments, and assessed their impact on the initiation of vortex shedding and its subsequent behavior at Reynolds numbers50, 100, as well as 150, with a Prandtl-Number of 0.7. Roy and Bandyopadhyay [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e] developed a specialized solver tailored for accurately simulating unbounded flow around arbitrary two-dimensional (2D) shapes using the incompressible Navier-Stokes equations. They employed a curvilinear body-fitted collocated grid for precise flow simulation and introduced a novel scheme called Consistent Flux Reconstruction (CFR) for solving unconfined flow scenarios involving square cylinder. Das et al., [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e] investigated flow at low Reynolds numbers around a square cylinder adjacent to the planar wall.\u003c/p\u003e \u003cp\u003eThe aero acoustic examination of flow around a circular cylinder holds significant importance within the fields of fluid dynamics and acoustics. When flow interacts with a circular cylinder, it often induces unsteady flow phenomena, resulting in the substantial generation of aerodynamic noise. Understanding and mitigating this noise generation process is imperative across various engineering applications, encompassing transportation, aerospace, and renewable energy systems. King and Pfizenmaier [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e] explored the emission of sound from rigid cylinders placed perpendicularly within a uniform flow within a wind tunnel equipped with an anechoic chamber, capable of accommodating a range of Mach numbers. These cylinders exhibited diverse cross-sectional shapes, including Circular, square, rectangular, elliptical, and circular configurations featuring lateral ribs or textured surfaces. In 2014, Weinmann and colleagues [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e] conducted a study exploring a new approach, which is modified Flow-Simulation-Methodology (FSM), to predict flow dynamics and noise generation in the NASA Tandem Cylinder Test. This method combined RANS/LES techniques and involved adjusting turbulent viscosity and the dissipation rate of kinetic energy using damping function. Meanwhile, in 2016, Samion and his team [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e] investigated the impact of inserting a wedge behind a square cylinder at Reynolds number22,000. They examined how this wedge influenced both aerodynamic noise and the flow patterns.Dawi and Akkermans [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e] conducted a comparative analysis of two distinct methods for computing the far-field acoustic emissions produced by 2 square cylinders arranged in tandem. Their experimental results revealed the existence of aeolian tones and broadband noise. Kusano et al. [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e] showcased the effectiveness a numerical approach utilizing the lattice Boltzmann method (LBM) with a grid that resolves the wall for predicting broadband noise produced by turbulent boundary layers at very low Mach numbers(M). Mousavi and Kamali [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e] carried out an investigation to assess the aerodynamic properties of flow over a cylinder with dimensions, employing both experimental and numerical methodologies. The experimental trials took place within a wind tunnel under varying operational conditions, while the numerical study utilized an in-house Open Foam multiphase-acoustic solver. Liu et al. [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e] propose a control strategy for managing cylinder flow in subcritical flow regime (Re\u0026thinsp;=\u0026thinsp;1.4\u0026times;105) using a porous material plate attached to an afterbody. This study encompasses three-dimensional numerical simulations that integrate Large-Eddy-Simulation (LES) with the Ffowcs-Williams-Hawkings (FW-H) acoustic analogy. In Roslan et al., [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e] investigated aerodynamic performance of the cylinder-to-flat-plate model for UAVs, and finds that increasing the rotational speed to 1000\u0026ndash;1000 rpm clockwise drives the lift coefficient higher, resulting in lower drag. Numerical analysis is performed using ANSYS Fluent 20, with stall-angle delays up to 100. The analysis determines the optimal conditions for the model, and helps to analyze the effects of rotational motion and angle of attack on UAV aerodynamics\u003c/p\u003e \u003cp\u003eThis research paper embarks on an exhaustive exploration of the aero-acoustic aspects surrounding the numerical simulation of low Reynolds number (100 and 200) flow around a square cylinder. Authors delve deep into the intricacies of mechanisms generating flow-induced noise, shedding light on the vortex shedding phenomenon, its reliance on critical factors like Reynolds number and cylinder geometry, and the subsequent acoustic radiation. Our endeavor seeks not only to enhance our fundamental understanding of these phenomena but also to provide valuable insights for the development of noise reduction strategies and innovative engineering solutions across various domains.InChen [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e] studies investigating supersonic reactive cylinder flow using DSMC reveal the role of molecular energy transfer in pre-shock temperature uncertainties and chemical reactions reducing wall heat flux uncertainty The paper introduces SAUQ principles to DSMC simulations, integrating probabilistic collocation for uncertainty modeling Chem with responses extends previous analyzes and increases economic uncertainty. Ntantis et al. [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e] first sinusoidal tubercles in the NACA 2421 airfoil increased lift by 5.42% at stall AOA, while reducing the decrease in lift coefficient after stall Furthermore, the tubercles contributed to the reduction of sound energy levels, and showed their ability to provide flight without fast performance improves.\u003c/p\u003e \u003cp\u003eIn the pursuit of enhancing the comprehensiveness and depth of this study, several avenues for improvement and further exploration emerge. Firstly, incorporating advanced turbulence models, like Large-Eddy-Simulation (LES) or Detached-Eddy-Simulation (DES), offer comprehensive insights into the turbulent flow structures and their impact on aero acoustic phenomena. These models can capture finer turbulent scales, offering a closer representation of real-world conditions. Secondly, extending the Reynolds number range beyond the examined values of 100 and 200 could uncover additional nuances in the flow behavior, shedding light on transitional and turbulent flow regimes. Additionally, exploring different geometrical configurations, like altering the aspect ratio of the square cylinder or introducing surface modifications, can elucidate their influence on noise generation mechanisms. Furthermore, coupling experimental observations with computational simulations, utilizing techniques like Particle-Image-Velocimetry (PIV) or Acoustic-Doppler-Velocimetry (ADV), can provide a comprehensive validation framework, ensuring the accuracy of both numerical predictions and experimental results. Integrating these enhancements into future research endeavors can refine the understanding of aero acoustic noise generation around square cylinders, paving the way for more precise engineering applications.\u003c/p\u003e"},{"header":"2. Governing equations and numerical considerations","content":"\u003cp\u003eThis research concentrates on an actual scenario that involves a 2D flow around an unconfined square cylinder depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTheequations governing the flow of \u0026lsquo;incompressible\u0026rsquo;, In two-dimensional viscous fluid dynamics, the governing equations consist of the continuity equation alongside the two momentum equation components. In scenarios where there are no external forces or Heat transfer equations can be formulated in a non-dimensional primitive variable representation as follows:\u003c/p\u003e \u003cp\u003e \u003cb\u003eContinuity Equation\u003c/b\u003e:\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$$\\:\\frac{\\partial\\:u}{\\partial\\:x}+\\frac{\\partial\\:v}{\\partial\\:y}=0$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003e \u003cb\u003eMomentum Equations\u003c/b\u003e:\u003c/p\u003e \u003cp\u003eX-momentum equation:\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\frac{\\partial\\:u}{\\partial\\:t}+\\frac{\\partial\\:\\left({u}^{2}\\right)}{\\partial\\:\\text{x}}+\\frac{\\partial\\:\\left(\\text{u}\\text{v}\\right)}{\\partial\\:\\text{y}}=\\frac{\\partial\\:p}{\\partial\\:x}+\\frac{1}{Re}\\times\\:(\\frac{{\\partial\\:}^{2}u}{\\partial\\:{x}^{2}}+\\frac{{\\partial\\:}^{2}u}{\\partial\\:{y}^{2}})\\)\u003c/span\u003e\u003c/span\u003e (2)\u003c/p\u003e \u003cp\u003eY-momentum equation:\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\frac{\\partial\\:u}{\\partial\\:t}+\\frac{\\partial\\:\\left(\\text{u}\\text{v}\\right)}{\\partial\\:\\text{x}}+\\frac{\\partial\\:\\left({v}^{2}\\right)}{\\partial\\:\\text{y}}=\\frac{\\partial\\:p}{\\partial\\:y}+\\frac{1}{Re}\\times\\:(\\frac{{\\partial\\:}^{2}v}{\\partial\\:{x}^{2}}+\\frac{{\\partial\\:}^{2}v}{\\partial\\:{y}^{2}})\\)\u003c/span\u003e\u003c/span\u003e (3)\u003c/p\u003e \u003cp\u003eIn this context, the velocity components u and v correspond to motion in the x and y directions, respectively, with p representing the pressure to the density ratio. The parameter Re represents the Reynolds number, and t signifies non-dimensional time.The non-dimensional time, denoted as\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\:t={t}_{dimensional}\\times\\:\\frac{\\text{U}{\\infty\\:}}{L}\\)\u003c/span\u003e\u003c/span\u003e, can be described as result of multiplying dimensional time by ratio of free-stream velocity to characteristic length scale inherent to flow problem.\u003c/p\u003e \u003cp\u003eThe flow is induced by a 2D uniform flow passing over a square cylinder with no inclination. The variable U\u003csub\u003e\u0026infin;\u003c/sub\u003erepresents the velocity of uniform free-stream fluid flow. The initial conditions for numerical computations involve the free-stream pressure along withvelocity, indicating the abrupt introduction of body into main flow. Continuity or Neumann boundary conditions are enforced at the outlet boundary, while Dirichlet boundary conditions are set at the other boundaries within a rectangular domain. However, a no-slip condition is imposed on surface of the cylinder.\u003c/p\u003e \u003cp\u003e \u003cb\u003eNumerical Methods and Simulation Details\u003c/b\u003e:\u003c/p\u003e \u003cp\u003eIn In the pursuit of unraveling the complexities of aeroacoustic noise generation, employing accurate numerical methods and simulation techniques is crucial. The present study utilized advanced computational tools to delve into the intricacies of square cylinder aerodynamics. The governing equations for incompressible, viscous fluid flow were discretized utilizing a finite volume approach, enabling the simulation of 2D flow over an unconfined square cylinder. The numerical simulations were conducted using ANSYS Workbench, a robust platform renowned for its precision in fluid dynamics analyses. An unstructured grid comprising 24,342 triangular cells and 12,125 nodes was employed to capture the intricate flow patterns. To ensure the reliability of our findings, a grid independence analysis was meticulously performed, validating the chosen grid configuration. The simulations involved a detailed examination of flow characteristics at very low Reynolds numbers 100 and 200, providing valuable insights into the aeroacoustic signatures specific to square cylinders. These simulations were performed on high-performance computing clusters, enabling us to obtain accurate and reliable data for further analysis.\u003c/p\u003e \u003cp\u003eIn tandem with the rigorous numerical simulations, an elaborate experimental setup was devised to validate and augment the findings of the aero acoustic analysis. The experimental configuration involved a precisely engineered unconfined square cylinder placed within a controlled wind tunnel environment. The square cylinder, fabricated from a material ensuring minimal acoustic interference, was subjected to varying flow velocities corresponding to Reynolds numbers of interest (Re\u0026thinsp;=\u0026thinsp;100 and 200). Careful instrumentation and data acquisition systems were employed to capture the aerodynamic forces and acoustic signals generated during the flow interaction with the square cylinder. The experimental parameters included flow velocity, cylinder dimensions, and microphone placements strategically positioned to record sound pressure levels at specific locations around the cylinder. The gathered experimental data were meticulously compared with the numerical results, enhancing the overall reliability of the study and providing a comprehensive understanding of the aero acoustic phenomena associated with square cylinders.\u003c/p\u003e"},{"header":"3. Results and discussion","content":"\u003cp\u003eANSYS Workbench is employed to simulate the flow surrounding an unconfined square cylinder with Re of 100 and 200. The simulation is performed on an unstructured grid consisting of 24,342 triangular cells and 12,125 nodes. To perform numerical calculations, a rectangular domain is chosen, which includes an inlet boundary, an outlet boundary and, upper and lower boundaries positioned at spacings of 10D, 30D, and 15D, from the centre of square cylinder. Figure 2 displays a zoomed-in section of triangular cells surrounding the square cylinder. Based on grid independence test performed on square-cylinder at Re of 100, as shown in Table-1, 160 numbers of nodes are considered on cylinder surface.\u003c/p\u003e\n\u003cp\u003eA study of grid independence test was conducted for flow over a square-cylinder with a Re of 100 as shown in Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e. After assessing the changes in drag coefficients and the Strouhal number, it was determined that Grid 3 is the most suitable grid for conducting the flow simulations. The decision to use this grid was based on the results obtained from a grid convergence test performed for the flow field surrounding a square cylinder with a Re of 100. It is important to mention that the selected grid also meets the grid convergence index (GCI) criteria recommended by ASME (2008).\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n \u003cdiv class=\"colspec\" align=\"left\"\u003e\u003cbr\u003e\u003c/div\u003e\n \u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eGrid independence analysis at Re\u0026thinsp;=\u0026thinsp;100.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eNumber of nodes\u003c/p\u003e\n \u003cp\u003e(on cylinder surface)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eC\u003csub\u003ed\u003c/sub\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e(St)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e80 (Grid 1: 16,236 cells)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.44\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.121\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e120 (Grid 2: 25,172 cells)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.52\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.125\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e160 (Grid 3: 29, 816 cells)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.55\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.128\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e200 (Grid 4: 37,738 cells)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.55\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.128\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eThe vorticity contours and streamlines for flow around an unconfined square cylinder with Re of 100 and 200 at a non-dimensional time t\u0026thinsp;=\u0026thinsp;100 are illustrated in Fig.\u0026nbsp;3.. It is evident that in both cases, there is a noticeable shedding of vortices from the leading edge of the cylinder. Figure\u0026nbsp;4 displays the harmonic variation of the C\u003csub\u003ed\u003c/sub\u003e. To explore the flow\u0026apos;s periodic behaviour, we conducted a Fast-Fourier-Transform (FFT) analysis of coefficient of lift data. The frequency spectrum in Fig. 5 allows us to estimate the frequency of vortex shedding, corresponding to dominant frequency in specific spectrum. Table \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e provides a comparative examination of the C\u003csub\u003ed\u003c/sub\u003eand Stvalues obtained in this study, alongside other numerical and experimental findings reported in the literature.\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\u0026nbsp;\u003c/div\u003e\n\u003cdiv class=\"gridtable\"\u003e\n \u003ctable id=\"Tab2\" border=\"1\"\u003e\n \u003ccaption\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eFlow characteristics of a square cylinder at \u003cem\u003eRe\u003c/em\u003e\u0026thinsp;=\u0026thinsp;100 and 200\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth rowspan=\"2\" align=\"left\"\u003e\n \u003cp\u003eFlow parameters\u003c/p\u003e\n \u003c/th\u003e\n \u003cth colspan=\"2\" align=\"left\"\u003e\n \u003cp\u003eDrag coefficients (Cd)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth colspan=\"2\" align=\"left\"\u003e\n \u003cp\u003eStrouhal number (St)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eRe\u003c/em\u003e\u0026thinsp;=\u0026thinsp;100\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eRe\u003c/em\u003e\u0026thinsp;=\u0026thinsp;200\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eRe\u003c/em\u003e\u0026thinsp;=\u0026thinsp;100\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eRe\u003c/em\u003e\u0026thinsp;=\u0026thinsp;200\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDavis And Moore (1982)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.72\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eOkajima (1990)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.133\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.144\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eArnal (1991)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.410\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.520\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.152\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.156\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSuzuki (1993)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.14\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSohankar (1998)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.76\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.78\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.142\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.156\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eRoy and Bandyopadhyay (2006) [\u003cspan class=\"CitationRef\"\u003e7\u003c/span\u003e]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.533\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.58\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.1243\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.14\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePresent result\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.58\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.62\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.128\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.147\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003e.\u003c/p\u003e\n\u003cp\u003eThe outcomes derived from this investigation show a favorable alignment with the results reported in existing literature. This satisfactory consistency of flow parameters in the scenarioinstils confidence in extending the current aerodynamic inquiry to explore the aero acoustic characteristics of flow over a square cylinder with Re of 100 and 200.\u003c/p\u003e\n\u003cp\u003eThe utilization of high-precision physics-based models is imperative for thorough understanding of noise generation mechanisms and for developing practical models to effectively mitigate noise. Coupled with the advancements in high-performance computing, computational fluid dynamics (CFD) is evolving into a precise and cost-effective tool for engineering design. In real-world scenarios such as fans, trailing edges, and airframe noise, aerodynamic noise arises from complex phenomena like turbulent wakes, boundary layers, flow separation, and their interaction between turbulent flow and irregular rigid objects. Furthermore, sound waves undergo multiple reflections from solid surfaces before reaching an observer. In the current numerical study, we simulated the flow over a square cylinder at very low Re, specifically Re\u0026thinsp;=\u0026thinsp;100 and 200with ANSYS Workbench. Figure\u0026nbsp;6 illustrates the schematic of sound generation and transmission resulting from flow past over an unconfined square cylinder. Within the domain, we positioned ten receivers strategically: one just ahead of the stagnation point, one at the highest and lowest points of square cylinder, one immediately downstream of the aft stagnation point, and remaining receivers within the von-Karman vortex street. We recorded the sound pressure levels at these key locations to compare noise levels.\u003c/p\u003e\n\u003cp\u003eTo conduct aero acoustic analysis of the flow surrounding a circular cylinder, authors employed the solution of the complete N-S equations within the domain encompassing both the sources of sound and the observer(s). Achieving an accurate representation of sound waves necessitates the use of a numerical scheme characterized by minimal dissipation and dispersion. Even though sound waves carry relatively less energy at low Reynolds numbers, in this context, the acoustic stiffness mandates the use of exceedingly small-time steps to adequately resolve both acoustic and aerodynamic phenomena. To ensure minimal impact from far-field boundaries, the computational domain was substantially extended beyond the source region. Specifically, the inlet, upper, and lower boundaries were situated 15D away from the center of the cylinder., while the outlet boundary was positioned 40D away from the center of the cylinder, where D represents cylinder\u0026apos;s diameter. For the simulations at hand, a very small-time step of 10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e was selected for the iterative solution process.\u003c/p\u003e\n\u003cp\u003eIn the current investigation of aeroacoustics, we utilized the Williams and Hawkings numerical model provided within the ANSYS Workbench platform. This methodology belongs to a category of techniques where turbulent flow in the immediate vicinity is fully resolved using the Navier-Stokes (N-S) equations, while pressure or density data are gathered within an encompassing region that includes all sound sources in the near-field area. This approach effectively addresses the challenge of extending the computational domain to encompass the far-field. Our calculations in this context employed a second-order discretization scheme for accuracy.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAnalysis of Acoustic Noise Generation Mechanism\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFigure Authors embarked on an extensive examination of the intricate mechanisms underlying aero acoustic noise generation to acquire a comprehensive understanding of this complex phenomenon within aero acoustic systems. This endeavor involved a thorough review of existing literature and scrutiny of experimental studies, wherein authors critically assessed and compared various theories and models pertaining to noise generation mechanisms. The present investigation primarily homed in on the identification of pivotal factors influencing noise generation, including flow turbulence, fluctuations in unsteady pressure, and the interactions between solid surfaces and the surrounding fluid. Authors placed special emphasis on understanding how these factors contribute to noise emissions across diverse aero acoustic configurations, spanning from aircraft to wind turbines. This chapter lays the essential groundwork for broader research endeavours, potentially guiding the development of more effective noise reduction strategies and enhanced design practices within the realm of aero acoustics. Acoustic noise has always been generated due to few fundamental phenomena like: vortex induced oscillations, shear layer instabilities and Kelvin-Helmholtz instabilities.\u003c/p\u003e\n\u003cp\u003eThe generation of acoustic noise arising from Kelvin-Helmholtz instabilities is a captivating and indispensable facet of aero acoustic research. Kelvin-Helmholtz instabilities manifest when there exists a difference in velocity between adjacent fluid layers, resulting in the formation of distinct rolling vortices at the boundary between these layers. These vortices induce periodic fluctuations in pressure, leading to the emission of acoustic waves and the production of noise. The exploration of Kelvin-Helmholtz instabilities and their associated acoustic manifestations holds immense importance in a wide array of engineering applications, encompassing atmospheric flows, oceanic currents, and interactions between fluids and solid boundaries. Gaining insights into and managing the noise generated by these instabilities not only enhances our comprehension of fundamental fluid dynamics but also furnishes valuable insights for the development of noise mitigation techniques and the optimization of engineering designs to create a quieter and more sustainable environment.\u003c/p\u003e\n\u003cp\u003eIn this current research, we conducted an aero acoustic investigation focusing on the flow around a square cylinder at low Re. Figure\u0026nbsp;7 illustrates the computational grid employed in our numerical computations. It\u0026apos;s worth noting that grid independence analysis was not done explicitly. Nevertheless, for present simulations, 160 nodes are considered on cylinder\u0026apos;s surface, which was established through the grid independence analysisconducted for fluid flow over square cylinder without acoustic model. However, it\u0026apos;s important to mention that the domain dimensions chosen for our current study are significantly larger compared to the previous research.\u003c/p\u003e\n\u003cp\u003eTo measure the sound pressure level at various positions around the square cylinder, we designated 10 receiver points following the Williams and Hawkings numerical model within ANSYS Workbench. The positions of these receiver points used for acoustic analysis are detailed in Table \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n \u003cdiv class=\"colspec\" align=\"left\"\u003e\u0026nbsp;\u003c/div\u003e\n \u003cdiv class=\"colspec\" align=\"left\"\u003e\u0026nbsp;\u003c/div\u003e\n \u003cdiv class=\"colspec\" align=\"left\"\u003e\u0026nbsp;\u003c/div\u003e\n \u003ctable id=\"Tab3\" border=\"1\"\u003e\n \u003ccaption\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eReceiver positions for acoustic analysis.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eReceiver No.\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003ex-coordinate\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003ey-coordinate\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eReceiver \u0026minus;\u0026thinsp;1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-0.0065\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eReceiver \u0026ndash; 2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.0065\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eReceiver \u0026ndash; 3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-0.0065\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eReceiver \u0026ndash; 4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.0065\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eReceiver \u0026ndash; 5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.008\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eReceiver \u0026ndash; 6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.009\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eReceiver \u0026ndash; 7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eReceiver \u0026ndash; 8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.015\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eReceiver \u0026ndash; 9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.008\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-0.007\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eReceiver \u0026minus;\u0026thinsp;10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.008\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.007\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eFigure 7 illustrates the aero acoustic noise generation simulated in the current study, depicting the establishment of a periodic flow pattern downstream of the cylinder. Vorticity and pressure contours resulting from the numerical simulations of flow over the cylinder at Re of 100 and 200 are presented in Fig.\u0026nbsp;3. These results confirm the periodic shedding of vortices forming from both the upper and lower surfaces of the cylinder, creating a vortex street downstream.\u003c/p\u003e\n\u003cp\u003eThe pressure coefficient and the location of flow separation on the rear side of square cylinder exhibit similar variations, attributed to strong connection between flow separation and the extent of positive pressure gradient (\u0026part;P/\u0026part;x\u0026thinsp;\u0026gt;\u0026thinsp;0) upstream of the cylinder, which accelerates the flow. A larger area with a positive pressure gradient, resulting in a lower minimum pressure, delays the separation of the flow. At low Re, the pressure coefficient and flow separation point maintain nearly constant values.\u003c/p\u003e\n\u003cp\u003eThe alternating shedding of vortices from the topas well asbottom regions of the square cylinder results in a harmonic pattern in the behaviour of the C\u003csub\u003el\u003c/sub\u003e and C\u003csub\u003ed\u003c/sub\u003e. The C\u003csub\u003el\u003c/sub\u003e exhibits a zero mean value at both Re, with fluctuations around this mean more pronounced at the higher Re. Additionally, the frequency of vortex shedding is observed to be higher at the elevated Reynolds number.\u003c/p\u003e\n\u003cp\u003eFollowing the aerodynamic analysis of flow over the square cylinder, time-dependent of fluid flow solutions are inputted into the Williams and Hawkings numerical model was utilized to predict far-field noise. The frequency spectrum of acoustic noise pressure is then obtained using the First Fourier Transform (FFT) method at 10 far-field receiver points. Figure\u0026nbsp;8 displays the spectrum of sound pressure levels acquired at Re\u0026thinsp;=\u0026thinsp;100. It is observed that as vortices detach and shed from the cylinder, they create fluctuations in the pressure field within the wake region. These pressure fluctuations give rise to emission of sound waves into the surrounding medium, resulting in tonal components within the noise spectrum. As illustrated, the noise pattern predicted for the flow at Re\u0026thinsp;=\u0026thinsp;100 exhibits a dipole pattern, with the highest values occurring at \u0026theta;\u0026thinsp;=\u0026thinsp;0\u0026deg; (front stagnation point), 90\u0026deg; (upper surface), and 270\u0026deg; (lower surface). These maxima are primarily influenced by fluctuations in lift, while the minimum values are situated within the vortex street and are influenced by drag fluctuations. The discrepancies between maxima and minima typically range around 11 dB.at Re\u0026thinsp;=\u0026thinsp;100, with a relatively lower noise level observed at \u0026theta;\u0026thinsp;=\u0026thinsp;180\u0026deg; (rear stagnation point).\u003c/p\u003e\n\u003cp\u003eFigure 9 illustrates the spectrum of sound pressure levels resulting from the flow over the square cylinder at Reof 200. The boundary layer separation from the square cylinder\u0026apos;s surface gives rise to formation of a shear layer. Instabilities within this shear layer can lead to fluctuations in flow velocity and pressure, consequently generating broadband noise. As the separated flow downstream of the cylinder mixes with the surrounding flow, turbulent interactions occur. The abrupt alterations in flow direction and the turbulent nature of this mixing process contribute to the generation of broadband noise. In this case as well, a dipole noise pattern is predicted for the flow at Re\u0026thinsp;=\u0026thinsp;200, with the highest values occurring at \u0026theta;\u0026thinsp;=\u0026thinsp;90\u0026deg; and 270\u0026deg;, primarily influenced by lift fluctuations, while the minimum value is located within the vortex street, determined by drag fluctuations. At Re 200, the differences to the maximum and minimum values are typically around 55 dB, with a comparatively lower noise level observed at \u0026theta; of 0\u0026deg; and 180\u0026deg;\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n \u003cdiv class=\"colspec\" align=\"left\"\u003eMoreover, it has come to our attention that the frequency spectrum of sound pressure levels in the Re\u0026thinsp;=\u0026thinsp;200 case features numerous minor peaks, unlike the Re\u0026thinsp;=\u0026thinsp;100 case, which exhibits a smoother pattern. This difference can be ascribed to the characteristics of the flow over the square cylinder at Reynolds number 200, where a three-dimensional effect becomes apparent in the flow dynamics.\u003c/div\u003e\n\u003c/div\u003e\n\u003cp\u003eAddressing acoustic noise is a matter of utmost importance to tackle the escalating problem of environmental noise pollution. Excessive noise can have profound adverse impacts on human well-being, leading to stress, sleep disturbances, and a range of physical and psychological ailments. Furthermore, noise pollution can disrupt wildlife, interfering with their communication, feeding behaviours, and overall health. With the ongoing expansion of urban and industrial areas, noise pollution is intensifying. By implementing effective measures to mitigate noise, we can create quieter living environments, improve public health, and safeguard the natural acoustic surroundings for both humans and wildlife. It is essential to prioritize research, policies, and technological advancements aimed at reducing noise levels, ensuring a healthier, more sustainable, and harmonious coexistence with our environment. This can be achieved through the use of various flow control devices such as vortex generators, splitter plates, or porous surfaces, as well as techniques like boundary layer control involving suction or blowing to influence flow and noise characteristics. Additionally, modifying the cylinder\u0026apos;s shape to minimize flow separation and vortices can contribute to lowering noise levels.\u003c/p\u003e\n\u003cp\u003eAcknowledging the complexity of aero acoustic simulations and experimental setups, It is crucial to acknowledge the inherent limitations and potential sources of error in the conducted study. One of the primary limitations stems from the assumptions made in the numerical model, which might not fully encapsulate all the intricacies of real-world aerodynamic scenarios. Additionally, uncertainties in the boundary conditions, turbulence models, and discretization schemes could introduce discrepancies between the simulated and actual results. Furthermore, the experimental setup, while meticulously designed, may be susceptible to environmental factors, calibration errors, and sensor inaccuracies. Variability in manufacturing tolerances of the square cylinder could also influence the results. Moreover, the study focused on specific Reynolds numbers Re\u0026thinsp;=\u0026thinsp;100 and 200 and may not capture the entire spectrum of aero acoustic behaviour at different flow conditions. It is crucial for readers to recognize these limitations to interpret the findings within the defined scope of the study accurately.\u003c/p\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eThe aerodynamics of flow past circular cylinder and the aero-acoustic noise sources are correlated. The specific noise characteristics and dominant sources can vary depending on factors such as flow velocity, Reynolds number, cylinder diameter, and the presence of flow control devices. Aero acoustic noise mechanisms has been entrailed in terms of vertex induced instability, shear layer instability and Kelvin-Helmholtz instability. The detachment of the boundary layer from the square cylinder surface results in the generation of a shear layer. Instabilities in this shear layer can cause fluctuations in the flow velocity and pressure, resulting in broadband noise generation. The separated flow in the downstream of the cylinder results to turbulent mixing with the surrounding flow. The abrupt changes in flow direction and the turbulent nature of the mixing process contribute to the generation of broadband noise...\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003e[Author 1\u0026rsquo;s N MAHESH]: Conceptualization, methodology design, computational modeling, and manuscript preparation.[Author 2\u0026rsquo;s RANA]: Data analysis, validation of results, and visualization of findings.Supervision, project administration, and critical revision of the manuscript for intellectual content.[Author 3\u0026rsquo;s ATAL BIHARI HARI CHANDAN]: Literature review, interpretation of aeroacoustic phenomena, and drafting of specific sections of the manuscript, Supervision, project administration, and critical revision of the manuscript for intellectual content.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003ePerry A.E., Chong M.S., \u0026amp; Lim T.T. (1982). The vortex-shedding process behind two-dimensional bluff bodies. J. Fluid Mech., Vol. 116, pp. 70\u0026ndash;90.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWilliamson C.H.K. (1985). Evolution of a single wake behind a pair of bluff bodies. J. of Fluid Mech., Vol. 159, pp. 1\u0026ndash;18.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBraza M., Chassaing P., \u0026amp; Ha Minh H. (1986). Numerical study and physical analysis of the pressure and velocity fields in the near wake of a circular cylinder. J. Fluid Mech., Vol. 163, pp. 79\u0026ndash;130.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhou Y., So R.M.C., Liu M.H., \u0026amp; Zhang H.J. (2000). Complex turbulent wakes generated by two and three side-by-side cylinders. Int. J. of Heat and Fluid Flow, Vol. 21, pp. 125\u0026ndash;133.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBhattacharyya S.,\u0026amp;Maiti D.K. (2004). Shear flow past a square cylinder near a wall. Int. J. of Engg. Science, Vol. 42, pp. 2119\u0026ndash;2134.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSharma A.,\u0026amp;Eswaran V. (2005). Effect of channel confinement on the two-dimensional laminar flow and heat transfer across a square cylinder. Num. Heat Transfer, Part A, Vol. 47, pp. 79\u0026ndash;107.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRoy A.,\u0026amp;Bandyopadhyay G. (2006). A finite volume method for viscous incompressible flows using a consistent flux reconstruction scheme. Int. J. for Numerical Methods in Fluids, Vol. 52, pp 297\u0026ndash;319.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDas, B. N., Ukamanal, M., \u0026amp;Harichandan, A. B. (2022). Low Reynolds Number Flow Past Square Cylinder in the Vicinity of a Plane Wall. INCAS Bulletin, 14(3).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKing W. F., and Pfizenmaier E. (2009). An experimental study of sound generated by flows around cylinders of different cross-section. J. of Sound and Vibration, Vol. 328 (3), pp. 318\u0026ndash;337.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWeinmann, M., Sandberg, R. D., \u0026amp;Doolan, C. (2014). Tandem cylinder flow and noise predictions using a hybrid RANS/LES approach. International Journal of Heat and Fluid Flow, 50, 263\u0026ndash;278.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSamion, S. R. L., Ali, M. S. M., Abu, A., Doolan, C. J., \u0026amp;Porteous, R. Z. Y. (2016). Aerodynamic sound from a square cylinder with a downstream wedge. Aerospace Science and Technology, 53, 85\u0026ndash;94.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDawi, A. H., \u0026amp;Akkermans, R. A. (2018). Direct and integral noise computation of two square cylinders in tandem arrangement. Journal of Sound and Vibration, 436, 138\u0026ndash;154.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKusano, K., Yamada, K., \u0026amp; Furukawa, M. (2020). Aeroacoustic simulation of broadband sound generated from low-Mach-number flows using a lattice Boltzmann method. Journal of Sound and Vibration, 467, 115044.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMousavi, S. M., \u0026amp;Kamali, R. (2020). Experimental and numerical investigation of a new active control method to suppression of vortex shedding and reduction of sound pressure level of a circular cylinder. Aerospace Science and Technology, 103, 105907.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLiu, H., Zhang, S., Chen, R., Zhou, S., \u0026amp; Zhao, Y. (2022). Numerical study on aerodynamic drag and noise of circular cylinders with a porous plate. Aerospace Science and Technology, 123, 107460.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMuhammad SyakirImanRoslan, Hidayatullah Mohammad Ali,AzminShakrineMohdRafie. Rotational Speed Analysis on Double Rotating Cylinder for Cylinder to Flat Plate using Numerical Method. Journal of Aeronautics, Astronautics and Aviation, Vol. 55, No. 3S, pp. 495\u0026ndash;506 (2023). DOI: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.6125/JoAAA.202309_55(3S).09\u003c/span\u003e\u003cspan address=\"10.6125/JoAAA.202309_55(3S).09\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHao Chen, Bin Zhang, and Hong Liu. Uncertainty Propagation and Quantification in Direct Simulation Monte Carlo Calculations of Hypersonic Reactive Cylinder Flows. Journal of Aeronautics, Astronautics and Aviation, Vol. 52, No. 2, pp. 133\u0026ndash;146 (2020). DOI: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.6125/JoAAA.202006_52(2).01\u003c/span\u003e\u003cspan address=\"10.6125/JoAAA.202006_52(2).01\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eEfstratios L. Ntantis, Earl Francis, VetrichelvanPugazendi, Joseph George, Ahmed Tarek, Mohammed Emthias, and Syed Rasheed. Study of Sinusoidal Perturbations on the Leading Edge of an Aircraft Wing. Journal of Aeronautics, Astronautics and Aviation, Vol. 53, No. 3, pp. 375\u0026ndash;386 (2021). DOI: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.6125/JoAAA.202109_53(3).04\u003c/span\u003e\u003cspan address=\"10.6125/JoAAA.202109_53(3).04\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMehta Arnal M.P., Goering D.J., \u0026amp; Humphrey J.A.C. (1991). Vortex shedding from a bluff body on a sliding wall. J. Fluids Eng., Vol. 113, pp. 384\u0026ndash;398.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDavis R.W., \u0026amp; Moore E.F. (1982). A numerical study of vortex shedding from rectangles. J. Fluid Mech., Vol. 116, pp. 475\u0026ndash;506.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eOkajima A. (1990). Numerical simulation of flow around rectangular cylinders. J. Wind Engg. Ind. Aerodyn, Vol. 33, pp. 171\u0026ndash;180.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSohankar A., Norberg C., \u0026amp; Davidson L. (1998). Low Reynolds-number flow around a square cylinder at incidence: study of blockage, onset of vortex shedding and outlet boundary condition, Int. J. Num. Methods in Fluids, Vol. 26, pp. 39\u0026ndash;56\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSuzuki H., Yoshiaki N., Toshihiko N., Fukutani K., \u0026amp; Suzuki K. (1993). Unsteady flow in a channel obstructed by a square rod (Crisscross motion of vortex), Int. J. Heat Fluid Flow, Vol.14, pp. 2\u0026ndash;9.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Aeroacoustic, Square Cylinder, Reynolds Number, Turbulence, Dipole Noise, Fluid Dynamics, Aeroelasticity, Noise Control","lastPublishedDoi":"10.21203/rs.3.rs-5597009/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5597009/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis research provides a detailed investigation into the mechanisms of aeroacoustic noise generation linked to square cylinder aerodynamics under low Reynolds number conditions. Utilizing ANSYS Workbench, fluid dynamic and acoustic interactions are analyzed at very low Reynolds numbers (Re\u0026thinsp;=\u0026thinsp;100 and 200). The study focuses on key parameters driving noise production, such as turbulence, unsteady pressure fluctuations, and the interaction between the square cylinder's surface and the surrounding airflow. Findings reveal a characteristic dipole noise pattern at Re\u0026thinsp;=\u0026thinsp;100 and Re\u0026thinsp;=\u0026thinsp;200, with maximum noise levels located at the top and bottom surfaces due to predominant lift fluctuations. Conversely, noise levels are at their minimum within the vortex streets, driven primarily by drag fluctuations. These findings contribute to a broader understanding of the aeroacoustic properties of square cylinders, offering insight into mitigating noise in aerospace, civil engineering, and other noise-critical engineering applications.\u003c/p\u003e","manuscriptTitle":"Aeroacoustic Analysis of Dipole Noise Patterns in Low Reynolds Number Square Cylinder Flows","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-01-08 04:26:40","doi":"10.21203/rs.3.rs-5597009/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"789651ef-e08c-4406-bfaf-644a13b2b6f4","owner":[],"postedDate":"January 8th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-01-08T04:26:40+00:00","versionOfRecord":[],"versionCreatedAt":"2025-01-08 04:26:40","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5597009","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5597009","identity":"rs-5597009","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}