Transition between the viscous and the inertial regime in sheared dense suspensions: the effect of wall boundaries

Transition between the viscous and the inertial regime in sheared dense suspensions: the effect of wall boundaries | 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 Transition between the viscous and the inertial regime in sheared dense suspensions: the effect of wall boundaries Alireza Khodabakhshi, Sudarshan Konidena, Franco Tapia, Alexandre Leonelli, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7490015/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 14 Mar, 2026 Read the published version in Acta Mechanica → Version 1 posted You are reading this latest preprint version Abstract The transition from the viscous to the inertial regime in dense suspensions remains incompletely understood. Volume-imposed rheometers, with fixed-gap confining walls, provide key insights into this transition by presenting rheology as shear and normal stress versus shear rate. However, the effects of wall boundaries on the rheological response, particularly in narrow-gap systems, which is relevant to many industrial and natural flows, are still not addressed. In this work, we conduct particle-resolved Direct Numerical Simulations (pr-DNS) of dense non-Brownian suspensions sheared between rough walls in a confined volume-imposed cell. Our results reproduce the general trend of the viscous-inertial transition observed in recent experiments. Importantly, consistent with experimental results, we captured a weakening of the effective friction coefficient during the transition. We demonstrate this behavior by introducing different cases changing the wall roughness and flow cell height. Both factors significantly influence stress levels by altering the layering of particles in the sheared suspension. All cases exhibit strong layering, but in the case with the roughest wall and weaker confinement, enhanced inter-layer mixing leads to higher stresses. After large strains, this regime transitions to a more structured, low-mixing regime, reducing stress to levels comparable to other cases. Despite the differences in stress values, all cases followed a consistent viscous-inertial transition trend. Microstruc-tural analysis revealed that the number of contacts reduces during the transition, yet the remaining contacts have larger force magnitudes, causing the transition to the inertial regime. Overall, we show that wall effects strongly influence layering and mixing, thereby shaping the rheological response of confined dense suspensions during the viscous-inertial transition. Volume-Imposed Rheology Dense Suspension Viscous-Inertial Transition Wall Boundaries Full Text Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 14 Mar, 2026 Read the published version in Acta Mechanica → 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-7490015","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":514686002,"identity":"0a28c129-7a9e-4d9e-8f38-f35e16ff3c94","order_by":0,"name":"Alireza Khodabakhshi","email":"","orcid":"","institution":"Technische Universität Dresden","correspondingAuthor":false,"prefix":"","firstName":"Alireza","middleName":"","lastName":"Khodabakhshi","suffix":""},{"id":514686003,"identity":"19c00189-1282-47e0-8d29-fe72f3bde333","order_by":1,"name":"Sudarshan Konidena","email":"","orcid":"","institution":"Technische Universität Dresden","correspondingAuthor":false,"prefix":"","firstName":"Sudarshan","middleName":"","lastName":"Konidena","suffix":""},{"id":514686004,"identity":"35517357-22e7-430f-a05c-5095e99027fa","order_by":2,"name":"Franco Tapia","email":"","orcid":"","institution":"Technische Universität Dresden","correspondingAuthor":false,"prefix":"","firstName":"Franco","middleName":"","lastName":"Tapia","suffix":""},{"id":514686005,"identity":"18eb2782-5d2a-4450-99b2-40538213bf18","order_by":3,"name":"Alexandre Leonelli","email":"","orcid":"","institution":"University of California, Santa Barbara","correspondingAuthor":false,"prefix":"","firstName":"Alexandre","middleName":"","lastName":"Leonelli","suffix":""},{"id":514686006,"identity":"09b40a8f-82ba-45c1-b483-988a5fa1115a","order_by":4,"name":"Bernhard Vowinckel","email":"data:image/png;base64,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","orcid":"","institution":"Technische Universität Dresden","correspondingAuthor":true,"prefix":"","firstName":"Bernhard","middleName":"","lastName":"Vowinckel","suffix":""}],"badges":[],"createdAt":"2025-08-29 15:38:27","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7490015/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7490015/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s00707-026-04640-6","type":"published","date":"2026-03-14T15:58:40+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":104739379,"identity":"9845e8d8-4e0f-458e-93c9-7c44b2282561","added_by":"auto","created_at":"2026-03-16 16:05:07","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":4899383,"visible":true,"origin":"","legend":"","description":"","filename":"KhodabakhshietalTransition.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7490015/v1_covered_7cc547ee-19b7-498d-a09d-44cf9c747aa2.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Transition between the viscous and the inertial regime in sheared dense suspensions: the effect of wall boundaries","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":true,"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":"Volume-Imposed Rheology, Dense Suspension, Viscous-Inertial Transition, Wall Boundaries","lastPublishedDoi":"10.21203/rs.3.rs-7490015/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7490015/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"The transition from the viscous to the inertial regime in dense suspensions remains incompletely understood. 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