CFD Analysis of Ducted Propeller Flow Field Characteristics

CFD Analysis of Ducted Propeller Flow Field Characteristics | 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 Article CFD Analysis of Ducted Propeller Flow Field Characteristics Yu-Shi Wang, Guan-Hong Pan, Cheung-Hwa Hsu, Cheng-hao Chen This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5767703/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 study investigates the flow field characteristics of ducted propellers and the impact of duct shape on thrust. Numerical simulations using computational fluid dynamics (CFD) and a sliding mesh model were conducted to analyze various duct shapes, lengths, and tip clearances. Results show that increasing duct length enhances the flow field, boosting propeller thrust. Conversely, larger tip clearance generates a low-speed flow field inside the duct, significantly reducing thrust. Notably, the thrust reduction from increased tip clearance outweighs the thrust gain from extended duct length. These findings underscore the critical role of duct length and tip clearance in optimizing ducted propeller design and efficiency. Ducted propellers Numerical simulation Computational Fluid Dynamics Sliding mesh model Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Introduction As science and technology continue to advance, various propeller methods have been developed for ships and other vessels. These include traditional propellers, as well as ducted propellers, water jets, and pod thrusters. Each propeller type is selected and installed on board according to the specific operating characteristics of the vessel to maximize its function and effectiveness. Ducted propellers are a type of propeller enclosed within a cylindrical duct, as shown in Fig. 1 . This structure not only protects the propeller but also features a relatively simple design compared to water jet propellers and pod thrusters. Additionally, ducted propellers are easier to operate and maintain, making them particularly suitable for smaller ships. This research focuses on the design configuration of ducted propellers. It aims to conduct numerical simulations of the flow field by combining various duct shapes with propellers. The goal is to analyze the overall effects of ducted propellers on the motion flow field and to explore how the shape of the duct influences the flow field and the thrust generated by the propeller. Overall, this study emphasizes the importance of selecting the appropriate propeller type for a given vessel to maximize efficiency and effectiveness. It also offers valuable insights into the design of ducted propellers, contributing to improved performance and broader suitability for various types of vessels. Literature review Investigates ducted marine propellers' hydrodynamic performance, emphasizing decelerating ducts' effects on efficiency and propulsion dynamics. Combining CFD and EFD, it explores thrust generation, hydrodynamic efficiency, and wake characteristics to optimize propulsion systems 1 , 2 . The study investigates the impact of duct geometry and propeller placement on hydrodynamic performance using computational fluid dynamics (CFD). Simulations are validated with experimental data, providing insights into optimizing marine duct designs by linking geometric parameters to propulsion efficiency 3 , 4 , 5 . The study investigates the hydrodynamic performance of an underwater vehicle equipped with ducted propellers under various movement conditions using computational fluid dynamics (CFD). By integrating structural and non-structural grids, the researchers constructed a model based on a specifically designed propeller arrangement. The CFD analysis conducted behind the hull incorporates wake effects, thrust deduction factors, and viscous effects directly into the simulation. Utilizing an interactive approach between the lifting line method and CFD processes, the study optimizes key parameters such as pitch, circulation, and camber to achieve the required thrust. This comprehensive analysis enhances the understanding of propeller-duct interactions and aids in the optimization of ducted propeller designs for improved propulsion efficiency in marine applications 6 , 7 , 8 . This study utilizes computer-aided design (CAD) software and computational fluid dynamics (CFD) simulations to identify the ducted propeller model with optimal efficiency. By analyzing various configurations, it evaluates performance under ducted conditions and compares it with open conditions (without a duct) to explore differences in propeller blade behavior. CFD analysis examines the effects of water flow velocity, considering different blade designs within ducted arrangements, to optimize hydrodynamic performance. The findings highlight the influence of duct presence, blade design, and flow dynamics on efficiency 9 , 10 , 11 . This study leverages computational fluid dynamics (CFD) to investigate the impact of varying duct configurations, including adjustments to duct clearance, curvature, and angle of attack. Additionally, it explores how changes in propeller blade angles influence the overall performance and efficiency of the propulsion system. By systematically modifying these parameters, the analysis aims to optimize hydrodynamic characteristics, such as thrust generation and flow dynamics, providing valuable insights into advanced design strategies for marine propulsion systems 12 , 13 , 14 , 15 , 16 . Model drawing and numerical analysis Model drawing of ducted propellers To investigate the influence of different duct shapes on the flow field and thrust of ducted propellers, drawing software was utilized to model the required duct and propeller for numerical simulation. The propeller has a diameter of 0.500 m and consists of four blades, as shown in Fig. 2 . To facilitate smooth mesh generation on the propeller’s surface, the propeller's blade and hub were modeled while omitting the shaft, simplifying the layout of the flow field computational domain. The outer duct is designed as a hollow cylinder, serving to guide the flow and protect the propeller from external disturbances and damage during operation, as illustrated in Fig. 3 . This design approach ensures accurate simulation results while maintaining practicality in terms of flow field analysis and ducted propeller performance evaluation. In this study, prior to designing ducted propellers of varying sizes, key parameters such as tip clearance, duct length, and the inner and outer diameters of the duct were analyzed, as illustrated in Fig. 4 . The length and diameters of the guide cover are defined, and the tip clearance is measured as the distance from the propeller blade tip to the inner edge of the guide cover. Using this model as a foundation, numerical simulations were conducted for four different duct sizes, as shown in Table 1 . This approach facilitates detailed analysis of the flow field around ducted propellers and examines the effects of varying duct shapes on the propeller’s flow field and overall simulation outcomes. These findings aim to enhance the understanding and optimization of ducted propeller performance. Table 1 Dimensions of different models of ducted propellers. Model Propeller Diameter (m) Inner Diameter (m) Tip Clearance (m) Length (m) 1 0.500 0.550 0.025 0.300 2 0.500 0.550 0.025 0.450 3 0.500 0.600 0.050 0.300 4 0.500 0.600 0.050 0.450 Mesh configuration of ducted propellers flow field To ensure smooth mesh generation and accurate numerical simulation for the propeller’s surface, which features significant curvature changes, this study employs an unstructured mesh configuration for the propeller blades and hub, as shown in Fig. 5 . For the cylindrical outer edge, a structured mesh is used, as it is easier to implement in such geometries. A structured mesh generally reduces the total number of elements, shortens computation time, and enhances numerical accuracy. However, creating structured meshes on surfaces with high curvature or irregularities often introduces high mesh skewness, which can negatively impact calculation precision. Therefore, this study carefully balances computational efficiency and accuracy by optimizing the number and placement of mesh points. This approach minimizes skewness while ensuring reliable simulation results within a reasonable timeframe. Mesh boundary condition setting of flow field calculation domain For the numerical simulation of the flow field around ducted propellers, the first step involves creating an independent mesh block encompassing the propeller. This block rotates along with the propeller, allowing the mesh within the block to simulate the rotational motion of the propeller during numerical calculations effectively. Next, boundary conditions for the computational domain of the overall flow field are defined. The upstream boundary is set as a velocity inlet, while the downstream boundary is set as a pressure outlet. The outer boundaries of the domain are assigned symmetry conditions. The surfaces of the propeller and the duct are treated as no-slip boundary conditions. These boundary conditions are illustrated in Fig. 6 . It is important to note that the quality of the mesh configuration and the selection of appropriate boundary conditions significantly influence the accuracy and efficiency of numerical simulations. Careful attention is required to balance computational time with the precision of the simulation results, ensuring reliable and efficient outcomes. Response resul and discussions Velocity field and pressure field analysis of ducted propellers After completing the numerical simulation of the ducted propellers, the velocity field distribution on the propeller's surface is analyzed, as shown in Fig. 7. The velocity distribution on both the blade surface and the blade back was obtained through the simulation. It is observed that the velocity on the propeller’s surface increases radially outward on both the blade surface and back, consistent with the velocity variation typical of a rotating propeller. Additionally, the velocity on the propeller hub’s surface, facing the incoming flow, is low or near static. This area acts as a stagnation point where the radial velocity is relatively low around the hub. In contrast, the velocity on the inner and outer edge surfaces of the shroud remains low due to being relatively distant from the influence of the flow field velocity generated by the propeller's rotation. These regions are largely in a state of low flow velocity, reflecting minimal interaction with the rotating flow field. (a) Propeller blade back (b) Propeller blade Figure 7. Velocity field distribution obtained from the numerical calculation of ducted propellers. The pressure distribution on the surface of the ducted propellers is analyzed, as shown in Fig. 8. The static pressure distribution on the propeller blade surface and back, obtained through numerical simulations, reveals key trends. The static pressure on the blade surface is generally higher than that on the blade back, which generates the net thrust necessary to propel ships. This difference emphasizes the blade surface's crucial role in thrust generation. Additionally, the propeller hub's surface facing the incoming flow field is a high-pressure region, representing a stagnation point where flow velocity is zero. Here, all dynamic pressure is converted into static pressure, resulting in a high-pressure state consistent with the physical principles governing propeller motion. These findings highlight the intricate interplay of pressure distribution and flow dynamics that underpin the thrust performance of ducted propellers. (a) Propeller blade back (b) Propeller blade Figure 8. Static pressure distribution obtained from the numerical calculation of ducted propellers. A closer examination of the pressure distribution on the surface of the ducted propellers, shown in Fig. 8, reveals notable variations along the inner edge of the guide cover. While these variations are not apparent in the velocity field distribution in Fig. 7, they are clearly evident in the pressure field distribution. The pressure changes in this area affect the velocity of the flow field entering the inner edge of the duct, highlighting the intricate interplay between pressure and velocity in the flow dynamics. Understanding the relationship between flow field velocity changes, the gap between the duct and the propeller, and the duct’s length will be an essential focus for future research. The reliable numerical results presented in the velocity field and static pressure distribution in Fig. 7, alongside the observed pressure variations in the guide cover's inner edge in Fig. 8, provide valuable insights for advancing knowledge in ducted propeller performance and design. A thrust value analysis of ducted propellers Figure 9 – 12 , show the time-varying thrust curves for ducted propellers calculated using four different models. In these figures, the "propeller" curve represents the thrust generated solely by the propeller, while the "ducted propellers" curve represents the combined thrust generated by the entire ducted propeller system. From the figures, it is evident that the thrust generated by the ducted propellers is not constant. At the initial stage of propeller rotation, a relatively high thrust is observed due to the numerical iterative calculations starting from a standstill and the boundary conditions applied. Over time, as the calculations progress, the thrust stabilizes and fluctuates within a specific range, a characteristic of thrust generated during propeller rotation. The thrust variations differ among the four models, as shown in Fig. 9 – 12 , Model 1 exhibits relatively stable thrust, while Models 2 to 4 experience a significant thrust drop between 8 and 10 seconds of simulation time. This drop may be attributed to changes in the gap between the propeller and the guide cover or variations in the length of the guide cover, highlighting the impact of the guide cover's internal geometry on thrust performance. Once stabilized, the thrust fluctuates within a limited range. Additionally, Fig. 9 – 12 , indicate that the thrust generated by the ducted propellers is consistently higher than that of the propeller alone. This demonstrates that the guide cover not only protects the propeller from external disturbances but also enhances its thrust performance. The ducted propeller design thus offers practical advantages without increasing maintenance complexity. Table 2 presents the thrust values of the ducted propellers, averaged over the stable thrust interval shown in Fig. 9 – 12 , The results indicate that increasing the length of the duct leads to a 3–6% increase in overall thrust. Conversely, increasing the gap between the propeller and the duct results in a reduction in thrust, with the effect being more pronounced in models with shorter ducts (approximately 7% reduction). However, this reduction is less significant in models with longer ducts. These findings highlight the importance of optimizing duct length and propeller gap for improved ducted propeller performance and efficiency. Table 2 Model 1–4 ducted propeller thrust values. Model Propeller thrust (N) Difference from Model 1 (%) Ducted propellers thrust (N) Difference from Model 1 (%) 1 2022.5 2055.4 2 2100.7 3.87 2203.7 7.22 3 1879.5 -7.07 1902.9 -7.42 4 1948.9 -3.64 2022.4 -1.61 Flow field analysis of ducted propellers The velocity field distribution profiles for the four models (Models 1–4) are shown in Fig. 13, From the figure, it is clear that Models 2 and 4, which feature longer duct lengths, enable the smooth discharge of large-scale, high-speed flow fields to the rear of the propeller. This characteristic contributes positively to increasing the thrust generated by the ducted propellers. Additionally, Fig. 13 reveals that Models 3 and 4, which have larger propeller clearances, exhibit a pronounced area of low-speed flow near the inner wall of the duct housing. These low-speed regions may increase frictional resistance along the inner wall of the duct housing, hindering the efficient passage of fluid through the internal space of the propeller and duct. This increased resistance could explain the reduction in thrust associated with larger propeller clearances. Finally, a numerical analysis of the velocity field, pressure field, thrust values, and flow field behavior of the ducted propellers across Models 1–4 highlights important trends. Increasing the length of the duct housing enhances propeller thrust, while increasing the clearance between the propeller and the inner edge of the duct results in a decrease in thrust. These findings underscore the necessity of carefully considering multiple external factors when designing ducted propellers to achieve optimal performance. Conclusions This study investigates the characteristics of the flow field in ducted propellers and examines the effects of changes in shroud shape on propeller thrust. Numerical simulations of flow fields were conducted using various duct configurations, with two key factors duct length and blade tip clearance as variables. Multiple ducted propeller models were developed to evaluate how these factors influence thrust performance. The analysis shows that increasing the length of the duct allows for a larger high-speed flow field to pass through the duct interior, facilitating smooth discharge to the rear of the propeller. This effect leads to a thrust increase of approximately 3–6%. Conversely, increasing the blade tip clearance results in the formation of extensive low-speed flow regions near the inner wall of the duct. These regions increase frictional resistance along the inner wall, hindering fluid flow through the propeller and duct space, which reduces thrust by about 7%. These findings emphasize the importance of optimizing duct length and blade tip clearance during the design process. Careful consideration of these factors is crucial to developing efficient ducted propellers tailored to specific applications. Discussion The Discussion should be succinct and must not contain subheadings. Methods Topical subheadings are allowed. Authors must ensure that their Methods section includes adequate experimental and characterization data necessary for others in the field to reproduce their work. Declarations Author contributions statement Y.W. conceived, planned, and performed the designs and drafted this paper. C.H provided guidance and reviewed this paper. Y.W., G.P. and C.C. provided the design ideas and edited this paper. All authors contributed to the article and approved the submitted version.All authors have read and agreed to the published version of the manuscript. Competing interests The authors declare no competing interests. Additional information Correspondence and requests for materials should be addressed to Y.W. References Bontempo, R.-M. et al. Performance analysis of ducted marine propellers. Part I – Decelerating duct. Journal Applied Ocean Research. 58 , 322-330 (2016). Villa, D.-M. et al. Numerical and Experimental Comparison of Ducted and Non-Ducted Propellers. Journal of Marine Science and Engineering . 8 (4), (2020). Celik, F.-S. et al. An Approach to the Design of Ducted Propeller. Mechanical Engineering. 17 (5), 406-417 (2010). Majdfar, S.-H. et al. Hydrodynamic Effects of the length and angle of the ducted propeller. Journal of Ocean, Mechanical and Aerospace -science and engineering . 25 , 19-25 (2015). Majdfar, S.-H. et al. 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Ocean Engineering . 123 , 116-130 (2016). Berlian, A. A. et al. CFD Letters Numerical Analysis into the Improvement Performance of Ducted Propeller by using Fins: Case Studies on Types B4-70 and Ka4-70. CFD Letters . 10, 12-42 (2024). Bontempo, R. et al. Ducted propeller flow analysis by means of a generalized actuator disk model. Energy Procedia . 45 , 1107-1115 (2014). Yongle, D.-W. et al. Numerical investigation of tip clearance effects on the performance of ducted propeller. International Journal of Naval Architecture and Ocean Engineering . 7 (2), 795-804 (2015). Chao, W et al. Prediction of hydrodynamic performance of pump propeller considering the effect of tip vortex. Ocean Engineering . 171 , 259-272 (2019). Chao, W et al. Analysis of influence of duct geometrical parameters on pump jet propulsor hydrodynamic performance. Journal of Marine Science and Technolog . 25 , 640-657 (2020). Zeyu, L.-L. et al. Numerical Analysis of the Effect of Ducted Propeller Configuration Parameters on Aerodynamic Performance. Journal of Physics Conference Series. 2361 (2022). 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-5767703","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":400515304,"identity":"04de7318-4597-45af-9211-98bd14696db8","order_by":0,"name":"Yu-Shi 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propellers with time in model 2.\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-5767703/v1/d4c51cace50c53352906f0e7.png"},{"id":73701305,"identity":"f64b574e-a1d5-4662-83fd-8af4635643a7","added_by":"auto","created_at":"2025-01-13 17:16:47","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":147465,"visible":true,"origin":"","legend":"\u003cp\u003eVariation curve of thrust of ducted propellers with time in model 3.\u003c/p\u003e","description":"","filename":"11.png","url":"https://assets-eu.researchsquare.com/files/rs-5767703/v1/a1fe11076fe0f1a2d64e6b2e.png"},{"id":73700694,"identity":"52a3af7d-ec12-4712-a6ff-10bea8e8c08d","added_by":"auto","created_at":"2025-01-13 17:08:39","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":146078,"visible":true,"origin":"","legend":"\u003cp\u003eVariation curve of thrust of ducted propellers with time in model 4.\u003c/p\u003e","description":"","filename":"12.png","url":"https://assets-eu.researchsquare.com/files/rs-5767703/v1/cff93606f1cf677dcb13eafe.png"},{"id":73700737,"identity":"96ec8792-06ec-4243-a4a2-e32591d22281","added_by":"auto","created_at":"2025-01-13 17:08:42","extension":"png","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":1374039,"visible":true,"origin":"","legend":"\u003cp\u003eVelocity field distribution profile of ducted propellers.\u003c/p\u003e","description":"","filename":"13.png","url":"https://assets-eu.researchsquare.com/files/rs-5767703/v1/06379a918b2cb32e62424ce3.png"},{"id":75287465,"identity":"0ae6b8aa-f3c5-4261-88aa-f2e167d54695","added_by":"auto","created_at":"2025-02-03 05:01:52","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":9611887,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5767703/v1/23ba55be-dd49-476d-9ba4-4c8ad11952c3.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"CFD Analysis of Ducted Propeller Flow Field Characteristics","fulltext":[{"header":"Introduction","content":"\u003cp\u003eAs science and technology continue to advance, various propeller methods have been developed for ships and other vessels. These include traditional propellers, as well as ducted propellers, water jets, and pod thrusters. Each propeller type is selected and installed on board according to the specific operating characteristics of the vessel to maximize its function and effectiveness.\u003c/p\u003e \u003cp\u003eDucted propellers are a type of propeller enclosed within a cylindrical duct, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. This structure not only protects the propeller but also features a relatively simple design compared to water jet propellers and pod thrusters. Additionally, ducted propellers are easier to operate and maintain, making them particularly suitable for smaller ships.\u003c/p\u003e \u003cp\u003eThis research focuses on the design configuration of ducted propellers. It aims to conduct numerical simulations of the flow field by combining various duct shapes with propellers. The goal is to analyze the overall effects of ducted propellers on the motion flow field and to explore how the shape of the duct influences the flow field and the thrust generated by the propeller.\u003c/p\u003e \u003cp\u003eOverall, this study emphasizes the importance of selecting the appropriate propeller type for a given vessel to maximize efficiency and effectiveness. It also offers valuable insights into the design of ducted propellers, contributing to improved performance and broader suitability for various types of vessels.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Literature review","content":"\u003cp\u003eInvestigates ducted marine propellers' hydrodynamic performance, emphasizing decelerating ducts' effects on efficiency and propulsion dynamics. Combining CFD and EFD, it explores thrust generation, hydrodynamic efficiency, and wake characteristics to optimize propulsion systems\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThe study investigates the impact of duct geometry and propeller placement on hydrodynamic performance using computational fluid dynamics (CFD). Simulations are validated with experimental data, providing insights into optimizing marine duct designs by linking geometric parameters to propulsion efficiency\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e,\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e,\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThe study investigates the hydrodynamic performance of an underwater vehicle equipped with ducted propellers under various movement conditions using computational fluid dynamics (CFD). By integrating structural and non-structural grids, the researchers constructed a model based on a specifically designed propeller arrangement. The CFD analysis conducted behind the hull incorporates wake effects, thrust deduction factors, and viscous effects directly into the simulation. Utilizing an interactive approach between the lifting line method and CFD processes, the study optimizes key parameters such as pitch, circulation, and camber to achieve the required thrust. This comprehensive analysis enhances the understanding of propeller-duct interactions and aids in the optimization of ducted propeller designs for improved propulsion efficiency in marine applications\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e,\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThis study utilizes computer-aided design (CAD) software and computational fluid dynamics (CFD) simulations to identify the ducted propeller model with optimal efficiency. By analyzing various configurations, it evaluates performance under ducted conditions and compares it with open conditions (without a duct) to explore differences in propeller blade behavior. CFD analysis examines the effects of water flow velocity, considering different blade designs within ducted arrangements, to optimize hydrodynamic performance. The findings highlight the influence of duct presence, blade design, and flow dynamics on efficiency\u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e,\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e,\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThis study leverages computational fluid dynamics (CFD) to investigate the impact of varying duct configurations, including adjustments to duct clearance, curvature, and angle of attack. Additionally, it explores how changes in propeller blade angles influence the overall performance and efficiency of the propulsion system. By systematically modifying these parameters, the analysis aims to optimize hydrodynamic characteristics, such as thrust generation and flow dynamics, providing valuable insights into advanced design strategies for marine propulsion systems\u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e,\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e,\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e,\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e,\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e"},{"header":"Model drawing and numerical analysis","content":"\u003ch2\u003eModel drawing of ducted propellers\u003c/h2\u003e\u003cp\u003eTo investigate the influence of different duct shapes on the flow field and thrust of ducted propellers, drawing software was utilized to model the required duct and propeller for numerical simulation. The propeller has a diameter of 0.500 m and consists of four blades, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e\u003cp\u003eTo facilitate smooth mesh generation on the propeller’s surface, the propeller's blade and hub were modeled while omitting the shaft, simplifying the layout of the flow field computational domain. The outer duct is designed as a hollow cylinder, serving to guide the flow and protect the propeller from external disturbances and damage during operation, as illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e.\u003c/p\u003e\u003cp\u003eThis design approach ensures accurate simulation results while maintaining practicality in terms of flow field analysis and ducted propeller performance evaluation.\u003c/p\u003e\u003cp\u003eIn this study, prior to designing ducted propellers of varying sizes, key parameters such as tip clearance, duct length, and the inner and outer diameters of the duct were analyzed, as illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e. The length and diameters of the guide cover are defined, and the tip clearance is measured as the distance from the propeller blade tip to the inner edge of the guide cover.\u003c/p\u003e\u003cp\u003eUsing this model as a foundation, numerical simulations were conducted for four different duct sizes, as shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. This approach facilitates detailed analysis of the flow field around ducted propellers and examines the effects of varying duct shapes on the propeller’s flow field and overall simulation outcomes. These findings aim to enhance the understanding and optimization of ducted propeller performance.\u003c/p\u003e\u003cdiv class=\"gridtable\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eDimensions of different models of ducted propellers.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003c/colgroup\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eModel\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePropeller Diameter (m)\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eInner Diameter (m)\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eTip Clearance (m)\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eLength (m)\u003c/p\u003e \u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.500\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.550\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.025\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.300\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.500\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.550\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.025\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.450\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.500\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.600\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.050\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.300\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.500\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.600\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.050\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.450\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/table\u003e\u003c/div\u003e\n\u003ch3\u003eMesh configuration of ducted propellers flow field\u003c/h3\u003e\n\u003cp\u003eTo ensure smooth mesh generation and accurate numerical simulation for the propeller\u0026rsquo;s surface, which features significant curvature changes, this study employs an unstructured mesh configuration for the propeller blades and hub, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e. For the cylindrical outer edge, a structured mesh is used, as it is easier to implement in such geometries.\u003c/p\u003e \u003cp\u003eA structured mesh generally reduces the total number of elements, shortens computation time, and enhances numerical accuracy. However, creating structured meshes on surfaces with high curvature or irregularities often introduces high mesh skewness, which can negatively impact calculation precision.\u003c/p\u003e \u003cp\u003eTherefore, this study carefully balances computational efficiency and accuracy by optimizing the number and placement of mesh points. This approach minimizes skewness while ensuring reliable simulation results within a reasonable timeframe.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\n\u003ch3\u003eMesh boundary condition setting of flow field calculation domain\u003c/h3\u003e\n\u003cp\u003eFor the numerical simulation of the flow field around ducted propellers, the first step involves creating an independent mesh block encompassing the propeller. This block rotates along with the propeller, allowing the mesh within the block to simulate the rotational motion of the propeller during numerical calculations effectively.\u003c/p\u003e \u003cp\u003eNext, boundary conditions for the computational domain of the overall flow field are defined. The upstream boundary is set as a velocity inlet, while the downstream boundary is set as a pressure outlet. The outer boundaries of the domain are assigned symmetry conditions. The surfaces of the propeller and the duct are treated as no-slip boundary conditions. These boundary conditions are illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e.\u003c/p\u003e \u003cp\u003eIt is important to note that the quality of the mesh configuration and the selection of appropriate boundary conditions significantly influence the accuracy and efficiency of numerical simulations. Careful attention is required to balance computational time with the precision of the simulation results, ensuring reliable and efficient outcomes.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\n\u003ch3\u003eResponse resul and discussions\u003c/h3\u003e\n\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eVelocity field and pressure field analysis of ducted propellers\u003c/h2\u003e \u003cp\u003eAfter completing the numerical simulation of the ducted propellers, the velocity field distribution on the propeller's surface is analyzed, as shown in Fig.\u0026nbsp;7. The velocity distribution on both the blade surface and the blade back was obtained through the simulation.\u003c/p\u003e \u003cp\u003eIt is observed that the velocity on the propeller\u0026rsquo;s surface increases radially outward on both the blade surface and back, consistent with the velocity variation typical of a rotating propeller. Additionally, the velocity on the propeller hub\u0026rsquo;s surface, facing the incoming flow, is low or near static. This area acts as a stagnation point where the radial velocity is relatively low around the hub.\u003c/p\u003e \u003cp\u003eIn contrast, the velocity on the inner and outer edge surfaces of the shroud remains low due to being relatively distant from the influence of the flow field velocity generated by the propeller's rotation. These regions are largely in a state of low flow velocity, reflecting minimal interaction with the rotating flow field.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e(a) Propeller blade back (b) Propeller blade\u003c/p\u003e \u003cp\u003e \u003cb\u003eFigure\u0026nbsp;7.\u003c/b\u003e Velocity field distribution obtained from the numerical calculation of ducted propellers.\u003c/p\u003e \u003cp\u003eThe pressure distribution on the surface of the ducted propellers is analyzed, as shown in Fig.\u0026nbsp;8. The static pressure distribution on the propeller blade surface and back, obtained through numerical simulations, reveals key trends.\u003c/p\u003e \u003cp\u003eThe static pressure on the blade surface is generally higher than that on the blade back, which generates the net thrust necessary to propel ships. This difference emphasizes the blade surface's crucial role in thrust generation. Additionally, the propeller hub's surface facing the incoming flow field is a high-pressure region, representing a stagnation point where flow velocity is zero. Here, all dynamic pressure is converted into static pressure, resulting in a high-pressure state consistent with the physical principles governing propeller motion.\u003c/p\u003e \u003cp\u003eThese findings highlight the intricate interplay of pressure distribution and flow dynamics that underpin the thrust performance of ducted propellers.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e(a) Propeller blade back (b) Propeller blade\u003c/p\u003e \u003cp\u003e \u003cb\u003eFigure\u0026nbsp;8.\u003c/b\u003e Static pressure distribution obtained from the numerical calculation of ducted propellers.\u003c/p\u003e \u003cp\u003eA closer examination of the pressure distribution on the surface of the ducted propellers, shown in Fig.\u0026nbsp;8, reveals notable variations along the inner edge of the guide cover. While these variations are not apparent in the velocity field distribution in Fig.\u0026nbsp;7, they are clearly evident in the pressure field distribution. The pressure changes in this area affect the velocity of the flow field entering the inner edge of the duct, highlighting the intricate interplay between pressure and velocity in the flow dynamics.\u003c/p\u003e \u003cp\u003eUnderstanding the relationship between flow field velocity changes, the gap between the duct and the propeller, and the duct\u0026rsquo;s length will be an essential focus for future research. The reliable numerical results presented in the velocity field and static pressure distribution in Fig.\u0026nbsp;7, alongside the observed pressure variations in the guide cover's inner edge in Fig.\u0026nbsp;8, provide valuable insights for advancing knowledge in ducted propeller performance and design.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eA thrust value analysis of ducted propellers\u003c/h3\u003e\n\u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e9\u003c/span\u003e\u0026ndash;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e12\u003c/span\u003e, show the time-varying thrust curves for ducted propellers calculated using four different models. In these figures, the \"propeller\" curve represents the thrust generated solely by the propeller, while the \"ducted propellers\" curve represents the combined thrust generated by the entire ducted propeller system.\u003c/p\u003e \u003cp\u003eFrom the figures, it is evident that the thrust generated by the ducted propellers is not constant. At the initial stage of propeller rotation, a relatively high thrust is observed due to the numerical iterative calculations starting from a standstill and the boundary conditions applied. Over time, as the calculations progress, the thrust stabilizes and fluctuates within a specific range, a characteristic of thrust generated during propeller rotation.\u003c/p\u003e \u003cp\u003eThe thrust variations differ among the four models, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e9\u003c/span\u003e\u0026ndash;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e12\u003c/span\u003e, Model 1 exhibits relatively stable thrust, while Models 2 to 4 experience a significant thrust drop between 8 and 10 seconds of simulation time. This drop may be attributed to changes in the gap between the propeller and the guide cover or variations in the length of the guide cover, highlighting the impact of the guide cover's internal geometry on thrust performance. Once stabilized, the thrust fluctuates within a limited range.\u003c/p\u003e \u003cp\u003eAdditionally, Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e9\u003c/span\u003e\u0026ndash;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e12\u003c/span\u003e, indicate that the thrust generated by the ducted propellers is consistently higher than that of the propeller alone. This demonstrates that the guide cover not only protects the propeller from external disturbances but also enhances its thrust performance. The ducted propeller design thus offers practical advantages without increasing maintenance complexity.\u003c/p\u003e \u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e presents the thrust values of the ducted propellers, averaged over the stable thrust interval shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e9\u003c/span\u003e\u0026ndash;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e12\u003c/span\u003e, The results indicate that increasing the length of the duct leads to a 3\u0026ndash;6% increase in overall thrust. Conversely, increasing the gap between the propeller and the duct results in a reduction in thrust, with the effect being more pronounced in models with shorter ducts (approximately 7% reduction). However, this reduction is less significant in models with longer ducts.\u003c/p\u003e \u003cp\u003eThese findings highlight the importance of optimizing duct length and propeller gap for improved ducted propeller performance and efficiency.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eModel 1\u0026ndash;4 ducted propeller thrust values.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eModel\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePropeller thrust (N)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eDifference from Model 1 (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eDucted propellers thrust (N)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eDifference from Model 1 (%)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2022.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2055.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2100.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e3.87\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2203.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e7.22\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1879.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e-7.07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1902.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e-7.42\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1948.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e-3.64\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e2022.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e-1.61\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e\n\u003ch3\u003eFlow field analysis of ducted propellers\u003c/h3\u003e\n\u003cp\u003eThe velocity field distribution profiles for the four models (Models 1\u0026ndash;4) are shown in Fig.\u0026nbsp;13, From the figure, it is clear that Models 2 and 4, which feature longer duct lengths, enable the smooth discharge of large-scale, high-speed flow fields to the rear of the propeller. This characteristic contributes positively to increasing the thrust generated by the ducted propellers.\u003c/p\u003e \u003cp\u003eAdditionally, Fig.\u0026nbsp;13 reveals that Models 3 and 4, which have larger propeller clearances, exhibit a pronounced area of low-speed flow near the inner wall of the duct housing. These low-speed regions may increase frictional resistance along the inner wall of the duct housing, hindering the efficient passage of fluid through the internal space of the propeller and duct. This increased resistance could explain the reduction in thrust associated with larger propeller clearances.\u003c/p\u003e \u003cp\u003eFinally, a numerical analysis of the velocity field, pressure field, thrust values, and flow field behavior of the ducted propellers across Models 1\u0026ndash;4 highlights important trends. Increasing the length of the duct housing enhances propeller thrust, while increasing the clearance between the propeller and the inner edge of the duct results in a decrease in thrust. These findings underscore the necessity of carefully considering multiple external factors when designing ducted propellers to achieve optimal performance.\u003c/p\u003e "},{"header":"Conclusions","content":"\u003cp\u003eThis study investigates the characteristics of the flow field in ducted propellers and examines the effects of changes in shroud shape on propeller thrust. Numerical simulations of flow fields were conducted using various duct configurations, with two key factors duct length and blade tip clearance as variables. Multiple ducted propeller models were developed to evaluate how these factors influence thrust performance.\u003c/p\u003e \u003cp\u003eThe analysis shows that increasing the length of the duct allows for a larger high-speed flow field to pass through the duct interior, facilitating smooth discharge to the rear of the propeller. This effect leads to a thrust increase of approximately 3\u0026ndash;6%. Conversely, increasing the blade tip clearance results in the formation of extensive low-speed flow regions near the inner wall of the duct. These regions increase frictional resistance along the inner wall, hindering fluid flow through the propeller and duct space, which reduces thrust by about 7%.\u003c/p\u003e \u003cp\u003eThese findings emphasize the importance of optimizing duct length and blade tip clearance during the design process. Careful consideration of these factors is crucial to developing efficient ducted propellers tailored to specific applications.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe Discussion should be succinct and must not contain subheadings.\u003c/p\u003e "},{"header":"Methods","content":"\u003cp\u003eTopical subheadings are allowed. Authors must ensure that their Methods section includes adequate experimental and characterization data necessary for others in the field to reproduce their work.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eAuthor contributions statement\u003c/p\u003e\n\u003cp\u003eY.W. conceived, planned, and performed the designs and drafted this paper. C.H provided guidance and reviewed this paper. Y.W., G.P. and C.C. provided the design ideas and edited this paper. All authors contributed to the article and approved the submitted version.All authors have read and agreed to the published version of the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests \u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAdditional information \u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCorrespondence\u003c/strong\u003e and requests for materials should be addressed to Y.W.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eBontempo, R.-M. et al. Performance analysis of ducted marine propellers. Part I \u0026ndash; Decelerating duct.\u003cem\u003e \u003c/em\u003e\u003cem\u003eJournal Applied Ocean Research. \u003c/em\u003e\u003cstrong\u003e58\u003c/strong\u003e, 322-330 (2016).\u003c/li\u003e\n\u003cli\u003eVilla, D.-M. et al. Numerical and Experimental Comparison of Ducted and Non-Ducted Propellers. \u003cem\u003eJournal of Marine Science and Engineering\u003c/em\u003e. \u003cstrong\u003e8\u003c/strong\u003e(4), (2020).\u003c/li\u003e\n\u003cli\u003eCelik, F.-S. et al. An Approach to the Design of Ducted Propeller. \u003cem\u003eMechanical Engineering.\u003c/em\u003e\u003cstrong\u003e17\u003c/strong\u003e(5), 406-417 (2010).\u003c/li\u003e\n\u003cli\u003eMajdfar, S.-H. et al. Hydrodynamic Effects of the length and angle of the ducted propeller. \u003cem\u003eJournal of Ocean, Mechanical and Aerospace -science and engineering\u003c/em\u003e. \u003cstrong\u003e25\u003c/strong\u003e, 19-25 (2015).\u003c/li\u003e\n\u003cli\u003eMajdfar, S.-H. et al. Hydrodynamic prediction of the ducted propeller by CFD solver. \u003cem\u003eJournal of Marine Science and Technology\u003c/em\u003e. \u003cstrong\u003e25\u003c/strong\u003e(3), 268-275 (2017).\u003c/li\u003e\n\u003cli\u003eSbragio, R.-S. et al. Design and CFD Self-Propulsion Analysis of a Ducted Propeller for a DARPA SUBOFF Hull Autonomous Underwater Vehicle. \u003cem\u003eProceedings of the ASME 2020 39th International Conference on Ocean, Offshore and Arctic Engineering.\u003c/em\u003e\u003cstrong\u003e1\u003c/strong\u003e (2020).\u003c/li\u003e\n\u003cli\u003eDai, Y. et al. CFD Simulation on Hydrodynamics of Underwater Vehicle with Ducted Propellers. \u003cem\u003eInternational Journal of Simulation Modelling. \u003c/em\u003e\u003cstrong\u003e20\u003c/strong\u003e, 595-605 (2021).\u003c/li\u003e\n\u003cli\u003eNanthagopal, S. CFD Analysis on Marine Propeller with Various Geometrical Conditions. \u003cem\u003eRecent Research Reviews Journal\u003c/em\u003e. \u003cstrong\u003e2\u003c/strong\u003e(2), 242-255 (2023).\u003c/li\u003e\n\u003cli\u003eBahatmaka, A.-H. et al. Ducted Propeller design and model analysis using CFD method for the optimization design of ROV. \u003cem\u003eProceedings of the Annual Autumn Conference,SNAK, Geoje\u003c/em\u003e. 688-696 (2015).\u003c/li\u003e\n\u003cli\u003eBhattacharyya, A. \u0026amp; Krasilnikov, V. A CFD-based scaling approach for ducted propellers. \u003cem\u003eOcean Engineering\u003c/em\u003e. \u003cstrong\u003e123\u003c/strong\u003e, 116-130 (2016).\u003c/li\u003e\n\u003cli\u003eBerlian, A. A. et al. CFD Letters Numerical Analysis into the Improvement Performance of Ducted Propeller by using Fins: Case Studies on Types B4-70 and Ka4-70. \u003cem\u003eCFD Letters\u003c/em\u003e. 10, 12-42 (2024).\u003c/li\u003e\n\u003cli\u003eBontempo, R. et al. Ducted propeller flow analysis by means of a generalized actuator disk model. \u003cem\u003eEnergy Procedia\u003c/em\u003e. \u003cstrong\u003e45\u003c/strong\u003e, 1107-1115 (2014).\u003c/li\u003e\n\u003cli\u003eYongle, D.-W. et al. Numerical investigation of tip clearance effects on the performance of ducted propeller. \u003cem\u003eInternational Journal of Naval Architecture and Ocean Engineering\u003c/em\u003e. \u003cstrong\u003e7\u003c/strong\u003e(2), 795-804 (2015).\u003c/li\u003e\n\u003cli\u003eChao, W et al. Prediction of hydrodynamic performance of pump propeller considering the effect of tip vortex. \u003cem\u003eOcean Engineering\u003c/em\u003e. \u003cstrong\u003e171\u003c/strong\u003e, 259-272 (2019).\u003c/li\u003e\n\u003cli\u003eChao, W et al. Analysis of influence of duct geometrical parameters on pump jet propulsor hydrodynamic performance. \u003cem\u003eJournal of Marine Science and Technolog\u003c/em\u003e. \u003cstrong\u003e25\u003c/strong\u003e, 640-657 (2020).\u003c/li\u003e\n\u003cli\u003eZeyu, L.-L. et al. Numerical Analysis of the Effect of Ducted Propeller Configuration Parameters on Aerodynamic Performance. \u003cem\u003eJournal of Physics Conference Series.\u003c/em\u003e 2361 (2022).\u003c/li\u003e\n\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"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":"Ducted propellers, Numerical simulation, Computational Fluid Dynamics, Sliding mesh model","lastPublishedDoi":"10.21203/rs.3.rs-5767703/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5767703/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis study investigates the flow field characteristics of ducted propellers and the impact of duct shape on thrust. Numerical simulations using computational fluid dynamics (CFD) and a sliding mesh model were conducted to analyze various duct shapes, lengths, and tip clearances. Results show that increasing duct length enhances the flow field, boosting propeller thrust. Conversely, larger tip clearance generates a low-speed flow field inside the duct, significantly reducing thrust. Notably, the thrust reduction from increased tip clearance outweighs the thrust gain from extended duct length. These findings underscore the critical role of duct length and tip clearance in optimizing ducted propeller design and efficiency.\u003c/p\u003e","manuscriptTitle":"CFD Analysis of Ducted Propeller Flow Field Characteristics","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-01-13 17:08:12","doi":"10.21203/rs.3.rs-5767703/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":"74f51fec-f6df-4b18-b51d-42527da1d0e4","owner":[],"postedDate":"January 13th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-02-03T04:53:37+00:00","versionOfRecord":[],"versionCreatedAt":"2025-01-13 17:08:12","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5767703","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5767703","identity":"rs-5767703","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}