Impulse and particle dislodgement under turbulent flow conditions

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dc.contributorVirginia Techen
dc.contributor.authorCelik, Ahmet Ozanen
dc.contributor.authorDiplas, Panayiotisen
dc.contributor.authorDancey, Clinton L.en
dc.contributor.authorValyrakis, Manousosen
dc.contributor.departmentMechanical Engineeringen
dc.date.accessed2013-11-20en
dc.date.accessioned2013-12-04T14:59:21Zen
dc.date.available2013-12-04T14:59:21Zen
dc.date.issued2010-04-01en
dc.description.abstractIn this study, we investigated the role of turbulence fluctuations on the entrainment of a fully exposed grain near threshold flow conditions. Experiments were carried out to measure synchronously the near bed flow velocity and the particle movement for a range of flow conditions and resulting particle entrainment frequencies. We used a simplified bed geometry consisted of spherical particles to reduce the complexities associated with the variations in the bed and flow details in an effort to identify the underlying dominant physical mechanism. An analysis was performed based on common force approximations using near bed flow velocity. Turbulence fluctuations were treated as impulses, which are products of magnitude and duration of applied force. It is demonstrated that besides the magnitude of the instantaneous forces applied on a sediment grain, their duration is important as well in determining whether a particle will be entrained by a turbulent flow event. Frequency of particle entrainment varied remarkably with minute changes in gross flow parameters. Impulse imparted on the sediment grain by turbulent flow was found to be well represented by a log-normal distribution. We obtained a (log-normal) probability density function (pdf) dependent on only the coefficient of variation of the impulse (impulse intensity). Relation of the impulse intensity to the particle Reynolds number, Re(*), was established. The sensitivity of the computed impulse to the critical force level, as well as the influence of the critical impulse level on the dislodgement events, was explored. Particle entrainment probabilities were found using the derived pdf as well as experimental observations and a good agreement between the two is reported. Implications of the presented impulse concept and our experimental findings for sediment mobility at low bed shear stress conditions are also discussed.en
dc.description.sponsorshipNational Science Foundation EAR-0439663,EAR-0738759en
dc.description.sponsorshipArmy Research Officeen
dc.format.mimetypeapplication/pdfen
dc.identifier.citationCelik, Ahmet O. and Diplas, Panayiotis and Dancey, Clinton L. and Valyrakis, Manousos, “Impulse and particle dislodgement under turbulent flow conditions,” Phys. Fluids (1994-present), 22, 046601 (2010), DOI:http://dx.doi.org/10.1063/1.3385433en
dc.identifier.doihttps://doi.org/10.1063/1.3385433en
dc.identifier.issn1070-6631en
dc.identifier.urihttp://hdl.handle.net/10919/24392en
dc.identifier.urlhttp://scitation.aip.org/content/aip/journal/pof2/22/4/10.1063/1.3385433en
dc.language.isoen_USen
dc.publisherAmerican Institute of Physicsen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectProbabilityen
dc.subjectTurbulenceen
dc.subjectTwo-phase flowen
dc.subjectSediment entrainmenten
dc.subjectIncipient motionen
dc.subjectShear stressen
dc.subjectBedsen
dc.subjectTransporten
dc.subjectProbabilityen
dc.subjectMovementen
dc.subjectProtrusionen
dc.subjectGrainsen
dc.titleImpulse and particle dislodgement under turbulent flow conditionsen
dc.title.serialPhysics of Fluidsen
dc.typeArticle - Refereeden
dc.type.dcmitypeTexten

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