Gravity-induced settling of many non-spherical particles at intermediate Galileo numbers: a DNS study

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The motion of ice particles in the atmosphere, of plankton in the oceans, and of suspended particles in chemical engineering apparatuses are some examples of sedimentation processes where the particle settling speed strongly depends upon their spatial distribution. Considerable progress in our fundamental understanding of suspension dynamics has already been gained through modern laboratory experiments and numerical analysis. However, most studies restrict their attention to spherically-shaped solids, although the majority of real-world applications such as the ones mentioned above involve non-spherical particles. In the present project we propose to study the settling behavior of ensembles of many spheroidal particles (both oblate and prolate) via interface-resolved direct numerical simulation (DNS) at low solid volume fraction and for particle Reynolds numbers of O(100. In this regime the modeling uncertainty of Euler-Lagrange (point-particle) models and of Euler-Euler (two-fluid) models is particularly high, and high-fidelity data for many non-spherical particles is practically non-existent. In the present project we plan to use the large data-set which will be generated in order to answer the following questions: How does particle shape influence the tendency to form wake-induced clusters? What are the consequences for the statistics of the particle motion? What is the impact upon the fluid flow induced by the settling particle ensemble? It can be expected that the thorough data analysis will allow us to make recommendations for reduced-order modelling of settling suspensions involving non-spherical particles.