Large‑Eddy Simulation Analysis of Momentum Balance and Turbulent Adjustment across a Forest‑to‑Clearing Roughness Change

Large‑Eddy Simulation Analysis of Momentum Balance and Turbulent Adjustment across a Forest‑to‑Clearing Roughness Change | 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 Large‑Eddy Simulation Analysis of Momentum Balance and Turbulent Adjustment across a Forest‑to‑Clearing Roughness Change Luis Aramis dos Reis Pinheiro, Rafael Castilho Farias Mendes, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6423152/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 Abrupt transitions from forest to clearing create complex shear layers, pressure gradients, and coherent vortices that challenge conventional atmospheric‑flow models. Here we apply large‑eddy simulation (LES) with a Localised Dynamic Kinetic sub‑grid model to reproduce a canonical forest–clearing configuration previously studied in a wind tunnel. The vegetation is represented through vertically distributed drag and leaf‑area density terms that absorb momentum and generate canopy turbulence. Model validation against particle‑image‑velocimetry and hot‑wire data demonstrates good agreement for mean velocity, friction velocity, and turbulence intensities within the canopy, while highlighting a systematic over‑prediction of the Reynolds stress (\overline{u'w'}) above the canopy. Momentum‑budget diagnostics reveal that advection, pressure gradients, and Reynolds‑stress divergences peak within five canopy heights of the edge, and that their combined effect sustains elevated turbulent stresses up to (x/h \approx 20). Beyond this fetch the flow relaxes: turbulent stresses decay, the internal boundary layer thickens, and the turbulent length scale (L_s) grows, indicating adjustment to the smoother clearing. Despite local discrepancies, the global momentum balance closes satisfactorily downstream of (x/h \approx 10), confirming that the dominant transport mechanisms are resolved. The results underscore the need to represent canopy heterogeneity and roughness discontinuities in mesoscale and climate models, and they establish LES as a robust framework for developing realistic parameterisations of fragmented landscapes with direct implications for pollutant dispersion, micro‑climate regulation, and land‑use planning. Forest-Clearing Transitions Large Eddy Simulation Turbulent Flow Dynamics Vegetation-Atmosphere Interactions Surface Roughness Effects Full Text 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-6423152","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":449171291,"identity":"2198ffbc-adec-48d3-9b30-1ff50242e8da","order_by":0,"name":"Luis Aramis dos Reis Pinheiro","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAzklEQVRIiWNgGAWjYLCCBCDmBzMKSNEi2QBiGJBik8EBMEmESv7Zh59uePDnXp7x+dWJHx4YMMjzix3Ar0XiXJrZjcS24mKzG283SwAdZjhzdgIBa84wALU0JCRuu3F2A0hLgsFtAlrkz7B/u5HwJyFx84yzm38QpcXgDI/ZjQS2hMQN/L3biLPF8AxPGdAvCcUSN3i3WSQYSBD2i9wZ9m03f/xJyOPvP7v55o8KG3l+aQJaYCCBQQKsUoI45RAt/AeIVz0KRsEoGAUjCwAAhg9JJMHVpB8AAAAASUVORK5CYII=","orcid":"","institution":"University of Brasília","correspondingAuthor":true,"prefix":"","firstName":"Luis","middleName":"Aramis dos Reis","lastName":"Pinheiro","suffix":""},{"id":449171292,"identity":"15c91dd1-328a-4f93-9f9f-150402a8789a","order_by":1,"name":"Rafael Castilho Farias Mendes","email":"","orcid":"","institution":"University of Brasília","correspondingAuthor":false,"prefix":"","firstName":"Rafael","middleName":"Castilho Farias","lastName":"Mendes","suffix":""},{"id":449171293,"identity":"8a2e27a1-c6c7-4a10-97b5-ab2014844f54","order_by":2,"name":"Mário Baptista de Siqueira","email":"","orcid":"","institution":"University of Brasília","correspondingAuthor":false,"prefix":"","firstName":"Mário","middleName":"Baptista","lastName":"de Siqueira","suffix":""},{"id":449171294,"identity":"580a3750-1adf-40f4-a44f-02be62149eaa","order_by":3,"name":"Antonio Cesar Pinho Brasil Jr","email":"","orcid":"","institution":"University of Brasília","correspondingAuthor":false,"prefix":"","firstName":"Antonio","middleName":"Cesar Pinho","lastName":"Brasil","suffix":"Jr"}],"badges":[],"createdAt":"2025-04-10 21:23:06","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6423152/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6423152/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":90205473,"identity":"fecb6bc2-785c-4d8a-9463-449d5e1ccc71","added_by":"auto","created_at":"2025-08-29 21:08:31","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2024596,"visible":true,"origin":"","legend":"","description":"","filename":"PaperFlorestaDegrauAramisEFDSpringerNat.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6423152/v1_covered_9f0781e5-a90e-4680-b29f-7de57b0017f0.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Large‑Eddy Simulation Analysis of Momentum Balance and Turbulent Adjustment across a Forest‑to‑Clearing Roughness Change","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"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":"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":"Forest-Clearing Transitions, Large Eddy Simulation, Turbulent Flow Dynamics, Vegetation-Atmosphere Interactions, Surface Roughness Effects","lastPublishedDoi":"10.21203/rs.3.rs-6423152/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6423152/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"Abrupt transitions from forest to clearing create complex shear layers, pressure gradients, and coherent vortices that challenge conventional atmospheric‑flow models. Here we apply large‑eddy simulation (LES) with a Localised Dynamic Kinetic sub‑grid model to reproduce a canonical forest–clearing configuration previously studied in a wind tunnel. The vegetation is represented through vertically distributed drag and leaf‑area density terms that absorb momentum and generate canopy turbulence. Model validation against particle‑image‑velocimetry and hot‑wire data demonstrates good agreement for mean velocity, friction velocity, and turbulence intensities within the canopy, while highlighting a systematic over‑prediction of the Reynolds stress \\(\\overline{u'w'}\\) above the canopy. Momentum‑budget diagnostics reveal that advection, pressure gradients, and Reynolds‑stress divergences peak within five canopy heights of the edge, and that their combined effect sustains elevated turbulent stresses up to \\(x/h \\approx 20\\). Beyond this fetch the flow relaxes: turbulent stresses decay, the internal boundary layer thickens, and the turbulent length scale \\(L_s\\) grows, indicating adjustment to the smoother clearing. Despite local discrepancies, the global momentum balance closes satisfactorily downstream of \\(x/h \\approx 10\\), confirming that the dominant transport mechanisms are resolved. 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