Direct Numerical Simulation of Rotating Ellipsoidal Particles using Moving Nonconforming Schwarz-Spectral Element Method.

We present application of a highly-scalable overlapping grid-based nonconforming Schwarz-spectral element method (Schwarz-SEM) to study the dynamics of rotating ellipsoidal particles. The current study is one of the first to explore the effect of rotation on ellipsoidal particles using fully resolved simulations (direct numerical simulation). The rotating ellipsoidal particles show substantial difference in the dynamics of the flow, when compared against non-rotating particles. The difference is primarily due to periodic attachment and separation of the flow to the surface of the particle for the rotating cases, which results in a higher drag on the particles when compared to the corresponding non-rotating cases. The dynamics is also different from a rotating spherical particle, where a steady shear layer develops near the surface of the sphere. For the rotating ellipsoidal particles, this mechanism results in a phase-difference between the position of observed maximum and minimum drag, and the position of expected maximum and minimum drag (i.e., maximum and minimum projected area). A similar phase-difference is also observed for the lift acting on the rotating ellipsoidal particles. The results presented here demonstrate the importance of explicitly modeling the shape and rotation of particles when we study the dynamics of non-spherical particles. Finally, the study also validates the use of non-conforming Schwarz-SEM for tackling problems in fully resolved particulate flow dynamics.