Translational and angular velocities statistics of inertial prolate ellipsoids in a turbulent channel flow up to Ret=1000

Direct numerical simulations of the turbulent flow in a channel are conducted up to Re-t = 1000 to examine the influence of the friction Reynolds number on the translational and angular velocities of inertial, prolate ellipsoids. The quadrant distribution of the turbulent events seen by the particles is not significantly affected by the value of Re-t, but subtle modifications take place, depending on the position in the channel and on the particle relaxation time. Overall, the influence of Re-t on the first and second statistical moments of the ellipsoids translational velocity is the same as that observed for the fluid velocity. The weak dependence of these statistics to the particle shape previously observed at low Reynolds number remains at higher values of Re-t. Similarly, the mean and root mean square (r.m.s.) of the angular velocity of the fluid seen by the particles weakly depend on particle shape and they have the same dependence to Re-t as the angular velocity statistics of the carrier fluid. Particle angular velocity statistics are more strongly affected by the flow Reynolds number due to the evolution of the complex shape and inertia dependent rotation orbits with Re-t. In the near-wall region the average angular velocity of weakly inertial ellipsoids increases with Re-t due to their stronger alignment with the mean fluid vorticity. Furthermore, the r.m.s. of the wall-nor mal component of the angular velocity of more inertial ellipsoids increases with Re-t owing to the larger fluctuations of the angle between the particle major axis and the velocity-gradient plane.

Automated summary

Direct numerical simulations are performed to investigate the influence of friction Reynolds number (Re_t) on the translational and angular velocities of inertial, prolate ellipsoids in turbulent channel flow. The quadrant distribution of the turbulent events experienced by the particles remains unchanged with varying Re_t, while subtle modifications occur depending on channel position and particle relaxation time. The statistical moments of the ellipsoids' translational velocity display the same dependence on Re_t as the fluid velocity, and the weak dependence on particle shape observed at low Reynolds numbers persists at higher Re_t. Similarly, the mean and r.m.s. of the particles' angular velocity weakly depend on particle shape and show the same dependence on Re_t as the fluid angular velocity statistics.