The influence of drag, lift and torque modelling on the dynamics of ellipsoidal particles in a turbulent channel flow

Abstract

Direct numerical simulation is coupled with a Lagrangian point-particle tracking to study the dynamics of inertial prolate ellipsoids in a turbulent channel flow. Two models are employed to compute the hydrodynamic force and torque acting on the ellipsoids in order to assess the influence of the fluid inertia. The first one is an analytical model derived under the assumption of a creeping flow motion at the particle scale while the second model relies on semi-empirical correlations to account for the effect of the fluid inertia on the hydrodynamic actions. For spherical and ellipsoidal particles alike, the hydrodynamic actions model has a weak influence on the probability density function of the particle Reynolds number and on their translational velocity statistics. The hydrodynamic actions modelling however strongly affects the near-wall rotation of weakly and moderately inertial ellipsoids, owing to the different rotation orbits favoured by the ellipsoids. This causes significant variations of the mean orientation and of the ellipsoids angular velocity statistics. In contrast, the rotational dynamics of highly inertial ellipsoids weakly depends on the hydrodynamic actions modelling in the near-wall region, but significantly varies in the buffer region. This effect is associated with the torque generated by the particle motion relative to the surrounding fluid, which results in a strong enhancement of the particle angular velocity fluctuations. Preferential alignment of the ellipsoids normal to the relative translational velocity vector is observed when the inertial effects are accounted for, corresponding to recent experimental observations and theoretical developments.