Direct Numerical Simulations of bed-load transport with non-spherical particles

This thesis presents the first highly resolved numerical simulations of sediment transport with a multitude of ellipsoidal particles of various shapes. To realize these simulations, the in-house code PRIME was extended with a constraint-based collision model for ellipsoids in a viscous media. Four phase-resolving Direct Numerical Simulations are conducted with monodisperse particles of different shapes (sphere, oblate, prolate, and tri-axial ellipsoid). The important quantities studied here are the mean particle velocities, the characteristic saltation length and period, the sediment-bed permeability, and the mean particle transport rate. By and large, the same two opposite extremes are observed in almost all mean quantities related to the disperse phase. At one end are the oblates, while at the other end are the spheres. The ellipsoids, which represent medium-size sand particles, behave in between these two extreme cases. Finally, an additional simulation is conducted using a set of particles which mimics a natural sand sample. To the best of the author’s knowledge, this simulation is the first of its kind and brings DNS of sediment transport with phase-resolved particles nearer to reality.