Intensifying fractal-grid-generated turbulence

Intensifying fractal-grid-generated turbulence | 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 Intensifying fractal-grid-generated turbulence Chandra Sekhar Kommineni, Jeremy Basley, Laurent Keirsbulck, Fethi Aloui This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8278679/v1 This work is licensed under a CC BY 4.0 License Status: Under Revision Version 1 posted 9 You are reading this latest preprint version Abstract For the past twenty years, fractal grids have shown their efficiency at generating long-lasting broad-band turbulence. So far, reference studies have mainly sought to develop the most canonical self-similar turbulence far downstream of the grid. The production region was stretched out, and the maximum turbulence intensities at the peak have remained limited. We explore a new part of the parameter space of \textit{fractal square grids} to accelerate turbulence production, shorten the wake interaction length, and consequently, enhance kinetic energy in the early stages of the turbulence in decay. The length/thickness ratio $L_0/t_0$ of the first iteration is much lower than that of typical grids in the literature. The experiments were conducted in a recirculating hydro-channel facility by means of Particle Image Velocimetry for spatially extended data and Laser Doppler Velocimetry for time-resolved centreline data. Based on the turbulence theory framework and comparing with the recent literature of grid-generated turbulence, the study focuses on characterising the production region and early stage of the decaying region, that is, within the wake interaction length ($x<x_*$). The analysis relies on centreline statistics, large-small-scale isotropy, characteristic length scales, and the spectral signature along the flow. The present findings are consistent with the nonequilibrium scaling reported in earlier studies of fractal–grid-generated turbulence. However, the new grids reveal that the dissipation scaling $C_\epsilon\sim\sqrt{Re_{L_0}}/Re_{\lambda}$ does not hold when geometries are extended to low $L_0/t_0$ ratios. Using the Reynolds number $Re_{t_0}$ % $=\frac{Re_{L_0}}{L_0/t_0}$ appears to be better suited, as it is more representative of the dynamics through initially injected vortex-shedding. The present findings are consistent with the nonequilibrium scaling reported in earlier studies of fractal–grid-generated turbulence. Turbulence theory nonequilibrium dissipation scaling Full Text Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Revision Version 1 posted Editorial decision: Revision requested 18 Jan, 2026 Reviews received at journal 18 Jan, 2026 Reviews received at journal 16 Jan, 2026 Reviewers agreed at journal 22 Dec, 2025 Reviewers agreed at journal 17 Dec, 2025 Reviewers invited by journal 16 Dec, 2025 Editor assigned by journal 07 Dec, 2025 Submission checks completed at journal 04 Dec, 2025 First submitted to journal 04 Dec, 2025 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-8278679","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":561747692,"identity":"41793b94-8d54-414e-8ea4-7842e5737353","order_by":0,"name":"Chandra Sekhar Kommineni","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABO0lEQVRIiWNgGAWjYBAC/hlAggfE4gGTCUDM2AAkJORA4h8YbDC0SNzApcUYKMQ4gyENQ4tBBKYWCEhswKVFuvnZg7d77Oz5ec4e/FzBkCanO+1w24OPOyzSN9zuPdjAkHAPQ4vMMXPDOc+SE2f29iVLnmHIMTa7ndhuOPOMRO6GO+eANiUUY2iRSDCT5jnAnGBwnsdAsoGhInHb7cQ2ad42oJYbOeYPGH8kYGpJ/wbUUm9vf57H+Cdcy982iXSDGzmGQFswtUTkgGw5zLiBt8cMaEsORAtjm0QCLi0SN3LKJOccOJ4448wZM8sGgzSQX9oke9skDGfeOWPYkICphX9G+jaJNweq7fl7coxvNlQky5ndTn8m8bOtTp7vdo9hwwdMLejuRHEBA3I8EQUkSFM+CkbBKBgFwxYAAM3gczxVFO/HAAAAAElFTkSuQmCC","orcid":"","institution":"Polytechnic University of Hauts-de-France","correspondingAuthor":true,"prefix":"","firstName":"Chandra","middleName":"Sekhar","lastName":"Kommineni","suffix":""},{"id":561747693,"identity":"193098c2-8f8d-4527-b9f9-c42d8f49c0ed","order_by":1,"name":"Jeremy Basley","email":"","orcid":"","institution":"Polytechnic University of Hauts-de-France","correspondingAuthor":false,"prefix":"","firstName":"Jeremy","middleName":"","lastName":"Basley","suffix":""},{"id":561747694,"identity":"0fe4f0f9-ac25-4e0b-915a-520f8717e524","order_by":2,"name":"Laurent Keirsbulck","email":"","orcid":"","institution":"Polytechnic University of Hauts-de-France","correspondingAuthor":false,"prefix":"","firstName":"Laurent","middleName":"","lastName":"Keirsbulck","suffix":""},{"id":561747695,"identity":"3b097af6-a30f-4448-8b70-6631c61922e8","order_by":3,"name":"Fethi Aloui","email":"","orcid":"","institution":"Polytechnic University of Hauts-de-France","correspondingAuthor":false,"prefix":"","firstName":"Fethi","middleName":"","lastName":"Aloui","suffix":""}],"badges":[],"createdAt":"2025-12-04 11:23:38","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8278679/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8278679/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":98555303,"identity":"ae301343-34c6-455d-b376-5a0f2a54ba4b","added_by":"auto","created_at":"2025-12-18 23:38:48","extension":"json","order_by":0,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":6289,"visible":true,"origin":"","legend":"","description":"","filename":"ed7fce81f5394d68b1956c90eec7c8bd.json","url":"https://assets-eu.researchsquare.com/files/rs-8278679/v1/dbf6249a5bc070e70c42c506.json"},{"id":98627958,"identity":"08e0a91a-2766-4f7e-a259-bffe96a87427","added_by":"auto","created_at":"2025-12-19 17:10:49","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":25242359,"visible":true,"origin":"","legend":"","description":"","filename":"FractalGridsKommineni.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8278679/v1_covered_8a3aabbf-03ea-43a2-b220-73fc5ffa523a.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Intensifying fractal-grid-generated turbulence","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"experiments-in-fluids","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"exif","sideBox":"Learn more about [Experiments in Fluids](http://link.springer.com/journal/348)","snPcode":"348","submissionUrl":"https://submission.nature.com/new-submission/348/3","title":"Experiments in Fluids","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Turbulence theory, nonequilibrium, dissipation scaling","lastPublishedDoi":"10.21203/rs.3.rs-8278679/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8278679/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"For the past twenty years, fractal grids have shown their efficiency at generating long-lasting broad-band turbulence. So far, reference studies have mainly sought to develop the most canonical self-similar turbulence far downstream of the grid. The production region was stretched out, and the maximum turbulence intensities at the peak have remained limited. We explore a new part of the parameter space of \\textit{fractal square grids} to accelerate turbulence production, shorten the wake interaction length, and consequently, enhance kinetic energy in the early stages of the turbulence in decay. The length/thickness ratio $L_0/t_0$ of the first iteration is much lower than that of typical grids in the literature. The experiments were conducted in a recirculating hydro-channel facility by means of Particle Image Velocimetry for spatially extended data and Laser Doppler Velocimetry for time-resolved centreline data. Based on the turbulence theory framework and comparing with the recent literature of grid-generated turbulence, the study focuses on characterising the production region and early stage of the decaying region, that is, within the wake interaction length ($x\u003cx_*$). The analysis relies on centreline statistics, large-small-scale isotropy, characteristic length scales, and the spectral signature along the flow. The present findings are consistent with the nonequilibrium scaling reported in earlier studies of fractal–grid-generated turbulence. However, the new grids reveal that the dissipation scaling $C_\\epsilon\\sim\\sqrt{Re_{L_0}}/Re_{\\lambda}$ does not hold when geometries are extended to low $L_0/t_0$ ratios. Using the Reynolds number $Re_{t_0}$ % $=\\frac{Re_{L_0}}{L_0/t_0}$ appears to be better suited, as it is more representative of the dynamics through initially injected vortex-shedding. The present findings are consistent with the nonequilibrium scaling reported in earlier studies of fractal–grid-generated turbulence.\n\n\n\n","manuscriptTitle":"Intensifying fractal-grid-generated turbulence","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-12-18 23:38:44","doi":"10.21203/rs.3.rs-8278679/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-01-19T02:23:59+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-01-18T23:50:45+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-01-16T13:22:04+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"135101096815433488899660862536272825312","date":"2025-12-22T14:04:08+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"316370519960545266162295227153293541814","date":"2025-12-17T11:27:23+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-12-16T13:46:10+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-12-07T17:51:27+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-12-05T02:46:23+00:00","index":"","fulltext":""},{"type":"submitted","content":"Experiments in Fluids","date":"2025-12-04T11:19:57+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"experiments-in-fluids","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"exif","sideBox":"Learn more about [Experiments in Fluids](http://link.springer.com/journal/348)","snPcode":"348","submissionUrl":"https://submission.nature.com/new-submission/348/3","title":"Experiments in Fluids","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"f24ef328-79ba-43aa-9588-af40cae1362e","owner":[],"postedDate":"December 18th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"in-revision","subjectAreas":[],"tags":[],"updatedAt":"2026-01-19T02:38:39+00:00","versionOfRecord":[],"versionCreatedAt":"2025-12-18 23:38:44","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8278679","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8278679","identity":"rs-8278679","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}