 Preferential concentration

Preferential concentration is the tendency of dense particles in a turbulent fluid to cluster in regions of high strain (low vorticity) due to their inertia.The extent by which particles cluster is determined by the Stokes number, defined as formula_1, where formula_2 and formula_3 are the timescales for the particle and fluid respectively; note that formula_4 and formula_5 are the mass densities of the fluid and the particle, respectively, formula_6 is the kinematic viscosity of the fluid, and formula_7 is the kinetic energy dissipation rate of the turbulence.