Wake-induced dynamics of anisotropic particles in homogeneous and shear flows

Dispersion of (low-density) rigid particle-laden flows with complex geometries is ubiquitous in both natural and industrial environments. We are usually interested in the particles' transport, deposition, and clustering in these systems. Furthermore, we would like to understand better how particles alter the flow field. Although, most systems are, in general, complex. To gain a better understanding, we concern ourselves with anisotropic particles and study how the anisotropy affects wake-induced particle dynamics. Here, we would like to find fundamental contributions which may apply to larger systems. For this, we performed numerical investigations at moderate Reynolds numbers. Anisotropy is introduced by systematically altering the particle shape and its mass distribution. We generally find high sensitivity to the latter parameters.

In Chapter 1, we started with implementation details and validations for the immersed boundary projection method (IBPM). Here, the problem of interest is a freely rising or falling cylinder with eccentric mass distribution, for which we solve the incompressible Navier-Stokes equations in a frame attached to the particle.

In Chapter 2, we explored rotational effects for a rising or settling cylinder with eccentric mass distribution in a quiescent fluid. For this work, we varied the mass offset, Galileo number (expressing gravity forces over viscous forces), density ratio, and moment of inertia. The particle is observed to undergo the resonance mode, where translational and rotational effects enhance each other, with the Magnus lift force at the base as the primary mechanism for a subset of buoyant density ratios.

In Chapter 3, we dealt with the dynamics of a freely moving buoyant sphere with eccentric mass distribution. In this study, we extend previous work to an unexplored Reynolds regime. The investigated regime extends from the onset of wake instabilities to where the wake breaks into smaller structures.

In Chapter 4, we explored shape and size effects for a prolate ellipsoid (of aspect ratio 4) in Taylor-Couette flow. Here, the set-up consists of a particle-laden flow between a rotating inner and a stationary outer cylinder. We found that the particles, which were initially randomly positioned, ultimately display characteristic spatial distributions.