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Heavy ellipsoids in creeping shear flow: Transitions of the particle rotation rate and orbit shape
KTH, School of Engineering Sciences (SCI), Mechanics, Fluid Physics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
2010 (English)In: Physical Review E - Statistical, Nonlinear, and Soft Matter Physics, ISSN 1539-3755, Vol. 81, no 1, 016323-1-016323-8 p.Article in journal (Refereed) Published
Abstract [en]

The motion of an inertial ellipsoid in a creeping linear shear flow of a Newtonian fluid is studied numerically. This constitutes a fundamental system that is used as a basis for simulations and analysis of flows with heavy nonspherical particles. The torque on the ellipsoid is given analytically by Jeffery [Proc. R. Soc. London, Ser. A 102, 161 (1922)]. This torque is coupled with the angular-momentum equation for the particle. The motion is then governed by the Stokes number St=rho(e)<(gamma)over dot>l(2)/mu, where rho(e) is the density of the ellipsoid, <(gamma)over dot> is the rate of shear, l is the length of the major axis of the ellipsoid, and mu is the dynamic viscosity of the fluid. For low St (the numerical value depends on the aspect ratio of the particle), the particle motion is similar to the Jeffery orbits obtained for inertia-free particles with the addition of an orbit drift so that the particle eventually lies in the flow-gradient plane. At higher St, more drastic effects are seen. For particles oriented in the flow-gradient plane, the rotation rate increases rather abruptly to half the shear rate in a narrow range of St. For particles with other orientations, the motion goes from a kayaking motion to rotation around an oblique axis. It is suggested that, depending on aspect and density ratios, particle inertia might be sufficient to explain and model orbit drift observed previously at low Reynolds numbers. It is discussed how and when the assumption of negligible fluid inertia and strong particle inertia can be justified from a fundamental perspective for particles of different aspect ratios.

Place, publisher, year, edition, pages
2010. Vol. 81, no 1, 016323-1-016323-8 p.
Keyword [en]
spheroidal particles, planar contraction, motion, orientation, dynamics, fibers, inertia, microgravity, suspensions, deposition
National Category
Fluid Mechanics and Acoustics
URN: urn:nbn:se:kth:diva-19408DOI: 10.1103/PhysRevE.81.016323ISI: 000277186200008ScopusID: 2-s2.0-76349122685OAI: diva2:337455
Swedish Research Council
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2011-01-18Bibliographically approved

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