Rotation of ellipsoids in canonical flows: Effects of particle and fluid inertia

Authors: Lundell, F., Rosén, T.
Document Type: Conference
Pubstate: Published
Journal: 23rd International Congress of Theoretical and Applied Mechanics, Beijing, China (2012)
Year: 2012


Rotation of ellipsoidal particles is a fundamental physical problem when modelling multiphase flows with non-spherical particles. The particle rotation is driven by the flow around the particle and the controlling parameters are the aspect ratios of the ellipsoid together with the Reynolds (Re) and Stokes (St) numbers, which measure the effects of fluid and particle inertia, respectively. These effects are studied in two canonical flows, shear flow and extensional flow, by numerical simulations. For shear flow, the effect of particle inertia at zero fluid inertia (creeping flow) has been scrutinized earlier and a complete description has been provided. It has been shown that as the particle inertia is increased, the rotation rate exhibits a transition that is fairly sharp in St. At this transition, the rotation changes from flipping with a long rotation period to steady rotation with a rotation rate equal to the vorticity. Here, some of these results are extended to the case of finite fluid inertia (Re > 0) . The transition is seen to move to higher Stokes numbers as Re is increased. For extensional flow, it is shown that the particle changes from direct alignment to damped oscillations as St is increased. The fastest alignment is found to occur for a non-zero value of the particle inertia. The insights from these (and similar) studies form a knowledge base that is necessary to master in order to understnad the motion of non-spherical particles in flows.