Dynamic Characterization of Transient Cavitation in a Kaplan Turbine Model during Large Grid Frequency Disturbances

Dynamic Characterization of Transient Cavitation in a Kaplan Turbine Model during Large Grid Frequency Disturbances | 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 Dynamic Characterization of Transient Cavitation in a Kaplan Turbine Model during Large Grid Frequency Disturbances Basel Al Bishtawi, Francesco Gerini, Gianfranco Scribano, Elena Vagnoni This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7966941/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 Tip leakage vortices are known to plague Kaplan turbines resulting in flow instabilities, noise, and cavitation erosion. This study investigates the tip leakage vortex cavitation (TLVC) experimentally on an emulated grid-coupled lab-scale Kaplan turbine during transient power stepping operations under two cavitation numbers, namely \((\sigma = 1.0)\) and \((\sigma = 0.6)\) . The two turbine power-stepping modes consist of runner rotational speed and blade angle variations. This is to characterize the behavior of the TLVC during turbine transient operation and to uncover underlying fluid-structure interactions with the blade. It is found that TLVC oscillates in two primary modes, namely 'breathing' and 'whipping', where 'breathing' takes place during any runner blade angle variation, while 'whipping' is induced by rotational speed variations. TLVC’s low frequency ‘breathing’ , under atmospheric conditions, plays a major role in inducing torque peaks on the blade, hence increasing the dynamic load on the blades. Additionally, 'whipping' generally appears to facilitate excessive blade torque signal jittering, which reflects stochastic loading on the blade. A suggested attribution to this is touchpoint formations along the blade surface. Based on their fluctuation analysis, turbines operating at \((\sigma = 1.0)\) seem to induce the most complex, unstructured blade loading, regardless of the power stepping direction. However, downward power stepping led to a stochastic blade torquing under \((\sigma = 0.6)\) flow regime. Tip Vortex Leakage Cavitation Kaplan Turbine Hydropower Transient State 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-7966941","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":555801876,"identity":"adc1bbd5-20ea-4baf-adec-4d6f32578709","order_by":0,"name":"Basel Al Bishtawi","email":"","orcid":"","institution":"University of Nottingham Malaysia","correspondingAuthor":false,"prefix":"","firstName":"Basel","middleName":"Al","lastName":"Bishtawi","suffix":""},{"id":555801880,"identity":"01c652fa-7d4c-4dc3-ad20-14908cba3302","order_by":1,"name":"Francesco Gerini","email":"","orcid":"","institution":"Ecole Polytechnique Fédérale de 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Disturbances","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":"Tip Vortex Leakage Cavitation, Kaplan Turbine, Hydropower, Transient State","lastPublishedDoi":"10.21203/rs.3.rs-7966941/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7966941/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eTip leakage vortices are known to plague Kaplan turbines resulting in flow instabilities, noise, and cavitation erosion. This study investigates the tip leakage vortex cavitation (TLVC) experimentally on an emulated grid-coupled lab-scale Kaplan turbine during transient power stepping operations under two cavitation numbers, namely \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\((\\sigma = 1.0)\\)\u003c/span\u003e\u003c/span\u003e and \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\((\\sigma = 0.6)\\)\u003c/span\u003e\u003c/span\u003e. The two turbine power-stepping modes consist of runner rotational speed and blade angle variations. This is to characterize the behavior of the TLVC during turbine transient operation and to uncover underlying fluid-structure interactions with the blade. It is found that TLVC oscillates in two primary modes, namely 'breathing' and 'whipping', where 'breathing' takes place during any runner blade angle variation, while 'whipping' is induced by rotational speed variations. TLVC\u0026rsquo;s low frequency \u003cem\u003e\u0026lsquo;breathing\u0026rsquo;\u003c/em\u003e, under atmospheric conditions, plays a major role in inducing torque peaks on the blade, hence increasing the dynamic load on the blades. Additionally, \u003cem\u003e'whipping'\u003c/em\u003e generally appears to facilitate excessive blade torque signal jittering, which reflects stochastic loading on the blade. A suggested attribution to this is touchpoint formations along the blade surface. Based on their fluctuation analysis, turbines operating at \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\((\\sigma = 1.0)\\)\u003c/span\u003e\u003c/span\u003e seem to induce the most complex, unstructured blade loading, regardless of the power stepping direction. However, downward power stepping led to a stochastic blade torquing under \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\((\\sigma = 0.6)\\)\u003c/span\u003e\u003c/span\u003e flow regime.\u003c/p\u003e","manuscriptTitle":"Dynamic Characterization of Transient Cavitation in a Kaplan Turbine Model during Large Grid Frequency Disturbances","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-12-08 07:47:04","doi":"10.21203/rs.3.rs-7966941/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":"3860d6d0-0da1-44cd-80da-f797b5dac90d","owner":[],"postedDate":"December 8th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-03-14T02:39:12+00:00","versionOfRecord":[],"versionCreatedAt":"2025-12-08 07:47:04","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7966941","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7966941","identity":"rs-7966941","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}