Collision Efficiency Calculations for Slightly Deformable and Spherical Drops

Abstract

Collision efficiency values are calculated for both slightly deformable drops and spherical liquid drops. For slightly deformable drops, subjected to combined gravitational and thermocapillary driving forces at small Reynolds numbers and Marangoni numbers, collision efficiency values vary with changing values of the ratio of the isolated gravitational drop velocity to that of the isolated thermocapillary drop velocity, the drop-to-medium viscosity ratio, and the drop-to-medium thermal conductivity ratio. Increases in the drop-to-medium viscosity and thermal conductivity ratios lead to significant decreases in the collision efficiency values. While for spherical liquid drops, as applied to raindrop growth, it is shown, for small Reynolds numbers, that the inclusion of Maxwell slip and retarded or unretarded van der Waals forces increases the collision efficiency values calculated for certain drop sizes and drop size ratios. Hydrodynamic and lubrication forces, internal drop circulation, weight, and buoyancy are also included in the calculations.