Gravity-induced settling of many non-spherical particles at intermediate Galileo numbers: a DNS study
Final Report Abstract
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 have studied the settling behavior of ensembles of many spheroidal particles (of moderately oblate type) via interface-resolved direct numerical simulation (PR-DNS) at low solid volume fraction and for particle Reynolds numbers of O(100). In this regime the modeling uncertainty of Euler-Lagrange (pointparticle) models and of Euler-Euler (two-fluid) models is particularly high, and high-fidelity data for many non-spherical particles has heretofore been very scarce. Here we have first validated our immersed-boundary-based approach with the aid of reference data from spectral/spectral-element simulations specifically for the case of non-spherical particles. This reference data is now available to the community for other studies in the future. We have then generated a large data-set involving many-particle suspensions and used it 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? We have been able to show that the tendency to form clusters arises from a fundamentally different mechanism than in the case of spheres. This conclusion is based upon series of auxiliary simulations involving isolated pairs of settling particles (undergoing drafting-kissing-tumbling) while systematically varying the initial conditions. These results have direct implications for reduced-order modelling of settling suspensions involving non-spherical particles.
Publications
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Suppl. mat. “A single oblate spheroid settling in unbounded ambient fluid: a benchmark for simulations in steady and unsteady wake regimes”. 4TU. ResearchData. Dataset.
M. Moriche, M. Uhlmann & J. Dušek
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A single oblate spheroid settling in unbounded ambient fluid: A benchmark for simulations in steady and unsteady wake regimes. International Journal of Multiphase Flow, 136, 103519.
Moriche, Manuel; Uhlmann, Markus & Dušek, Jan
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Efficient methods for particle-resolved direct numerical simulation. Modeling Approaches and Computational Methods for Particle-Laden Turbulent Flows, 147-184. Elsevier.
Uhlmann, Markus; Derksen, Jos; Wachs, Anthony; Wang, Lian-Ping & Moriche, Manuel
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On the clustering of low-aspect-ratio oblate spheroids settling in ambient fluid. Journal of Fluid Mechanics, 963.
Moriche, Manuel; Hettmann, Daniel; García-Villalba, Manuel & Uhlmann, Markus
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Suppl. anim. “on the clustering of low-aspect-ratio oblate spheroids settling in ambient fluid”. KITopen, 2023. Dataset.
M. Moriche, D. Hettmann, M. García-Villalba & M. Uhlmann
