Seminarium Zakładu Mechaniki i Fizyki Płynów

Collision of drops with inertia effects in strongly sheared linear flow fields

prof. dr hab. Francois Feuillebois, Ecole Superieure de Physique et de Chimie Industrielles, Paris, France

środa, 20 marca 2002

The relative motion of drops in shear flows is responsible for collisions leading to the creation of larger drops. Collisions of drops are calculated and the efficiency of collision is derived in typical linear flow fields: pure shear flow, pure straining motion. The shear rate of these fields is strong enough for sedimentation effects to be negligible. The Reynolds number is small enough for the flows outside and inside drops to be in the creeping flow regime, but the inertia of drops in their motion is taken into account. Van der Waals forces are also considered. Results for the collision efficiency in a pure shear flow show a remarkable threshold for some value of the ratio of drop radii, regardless of the Stokes number (viz. of drop inertia). Results for a pure straining motion show that the collision efficiency increases regularly with the Stokes number and may be quite larger than unity. * to appear : F. Pigeonneau & F. Feuillebois, J. Fluid Mech., 455, 359 (2002).