DNS experiments on the settling of heavy particles in homogeneous turbulence: two-way coupling and Reynolds number effects

Abstract

The present study addresses the effects of two-way fluid-particle interaction (“two-

way coupling”) on the settling of heavy particles in homogeneous turbulence. The

modification of turbulence by the particles and the resulting effects on the settling

velocity are analyzed by taking into account Reynolds number effects. The turbulent

carrier fluid phase is resolved by direct numerical simulation (DNS) and the particle

phase by the Lagrangian point-particle approximation. Results are presented for two

Taylor microscale Reynolds numbers R λ = 40 and 130. While for R λ = 40 the

Kolmogorov time scale, t η , is found almost unaltered by the two-way coupling, it

is found significantly decreased for R λ = 130. The consequent modification of the

particle Stokes number St = τ p /t η , τ p being the particle response time, shows that

comparisons between one-way coupling numerical data and two-way coupling numerical

or experimental data may be inconsistent. This is particularly relevant for the particle

settling in turbulence which has been previously shown to be strongly influenced by

the dynamical interaction of the small flow scales with the particles.