Instantaneous turbulent forces and impulse on a rough bed: Implications for initiation of bed material movement

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dc.contributor.authorCelik, Ahmet Ozanen
dc.contributor.authorDiplas, Panayiotisen
dc.contributor.authorDancey, Clinton L.en
dc.contributor.departmentCivil and Environmental Engineeringen
dc.contributor.departmentMechanical Engineeringen
dc.date.accessed2014-01-31en
dc.date.accessioned2014-02-05T14:20:25Zen
dc.date.available2014-02-05T14:20:25Zen
dc.date.issued2013-04-01en
dc.description.abstractThe overall objective of this study is to identify the physical mechanisms responsible for the entrainment of an exposed particle subject to rapidly fluctuating hydrodynamic forces in the case of channel flow with a fully rough boundary. This is pursued here by examining particle dislodgment under uniform and cylinder wake-flow experiments. The critical impulse concept is investigated more rigorously by measuring directly the pressures at four points on the surface of a fixed test grain. The number of impulse events determined from these experiments increases by more than an order of magnitude, over a modest change of roughness Reynolds number. Furthermore, they are well described by a log-normal probability density function. Both results are consistent with those obtained from similar experiments via indirect (velocity-based) impulse calculations and reported in a prior contribution. This comparison supports the use of the velocity record for determining instantaneous hydrodynamic forces and impulses instead of the more difficult approach of measuring the pressure fluctuations directly. The present results demonstrate the dominant role the local, streamwise velocity component plays on particle dislodgment. This is attributed to the large impulse content and occasionally strong positive lift force associated with flow events, exhibiting pronounced positive streamwise velocity fluctuations. The majority (approximate to 70%) of these events occur in the fourth quadrant, while a significant number (approximate to 22%) appear as first-quadrant episodes. It was also determined that wake flows can increase substantially particle entrainment via enhanced lift and increased turbulence intensity.en
dc.description.sponsorshipNational Science Foundation EAR-0439663, EAR-0738759, CBET-1033196en
dc.format.mimetypeapplication/pdfen
dc.identifier.citationCelik, A. O., P. Diplas, and C. L. Dancey (2013), Instantaneous turbulent forces and impulse on a rough bed: Implications for initiation of bed material movement, Water Resour. Res., 49, 2213-2227, doi:10.1002/wrcr.20210.en
dc.identifier.doihttps://doi.org/10.1002/wrcr.20210en
dc.identifier.issn0043-1397en
dc.identifier.issn1944-7973en
dc.identifier.urihttp://hdl.handle.net/10919/25325en
dc.identifier.urlhttp://onlinelibrary.wiley.com/doi/10.1002/wrcr.20210/pdfen
dc.language.isoenen
dc.publisherAmerican Geophysical Unionen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectIncipient motionen
dc.subjectImpulseen
dc.subjectForce fluctuationsen
dc.subjectSediment entrainmenten
dc.subjectBursting phenomenonen
dc.subjectParticle movementen
dc.subjectFlow conditionsen
dc.subjectTransporten
dc.subjectMotionen
dc.titleInstantaneous turbulent forces and impulse on a rough bed: Implications for initiation of bed material movementen
dc.title.serialWater Resources Researchen
dc.typeArticle - Refereeden
dc.type.dcmitypeTexten

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