Abstract
Effects of mass density ratio on clustering of small particles in a homogeneous isotropic turbulence have been investigated by direct simulations of the Navier-Stokes equations. An emphasis is placed on particles with small excess density, which are representative to those encountered in marine and aquatic environments. It is found that particles with specific gravity of 1:005 exhibit a weak preferential concentration, only when the fluid and particle velocities are initially not the same. The non-uniform distribution of particles is a transient phenomenon and disappears in a period of several tens of the Kolmogorov time scale. With increasing the specific gravity, the particle distribution becomes non-uniform, irrespective of the initial conditions. It is shown that the extent of preferential concentration does not depend on the particle specific gravity any more when it reaches to around 100.
