Acceleration statistics of prolate spheroidal particles in turbulent channel flow

Abstract

Computation of a dilute suspension of prolate spheroidal particles in a turbulent channel flow is undertaken to study the influence of inertia and shape on acceleration statistics. A pseudo-spectral direct numerical simulation is coupled with Lagrangian tracking under the one-way coupling assumption. Simulations are carried out at friction Reynolds number $\mathit{Re}_\tau = 1440$, for three aspect ratios $\lambda = 1, 3$ and $10$, and two Stokes numbers $\mathit{St} = 5$ and $30$. Results indicate that, as a consequence of the filtering effect of inertia, particle acceleration RMS decreases with increasing inertia. In addition, the normalised streamwise acceleration PDFs depart from that of the conditional fluid and their tails become narrower as inertia is increased. Furthermore, acceleration statistics show that particle elongation has a significant effect on the mean drag and on the particle selective sampling. Moreover, the classification of elongated particle behaviour in turbulent channel flow based on a global Stokes number is questioned. The zero-crossing acceleration autocorrelation timescales presented points out the need for a local dimensionless number estimation adapted to the case of prolate spheroids.

Publication
Journal of Turbulence
Juan Ignacio Polanco
Juan Ignacio Polanco
Postdoctoral researcher