The Effect of Particle Shape on the Dynamics of Suspensions of Spheroidal Particles

The effect of the shape on the dynamics of a suspension of non-spherical heavy particles is examined by fully resolved numerical simulations of oblate and prolate spheroids, as well as spheres, for a density ratio of ten, volume fractions ranging from 0.5% to 5%, and a Reynolds number between 20 and 30. The dynamics is determined both by the interactions of the particles with the fluid as well as by collisions, with the number and importance of collisions increasing with volume fractions. A single oblate and prolate spheroid fall broadside-on and at low volume fractions this is the predominant orientation. At higher volume fractions the orientation is more random. The various averaged quantities for prolate and oblate spheroids are similar and different from what is seen for spheres, particularly for low volume fractions. While the average slip velocity of the particles generally decreases with volume fraction, the orientation angle has an important role and as interactions and collisions orient some particles such that their smallest projected area faces the flow direction, they fall faster and the average particle slip velocity of the suspension is increased. The effect of particle orientation on the dynamics is obviously not captured by simulations with spherical particles.