A Generalized Form for Impact Velocities Used to Determine Graupel Accretional Densities

Abstract

A simple parameterization is presented which allows calculation of surface averaged radial impact velocities for droplets colliding with spheres as a function of the Reynolds and Stokes numbers. These impact velocities are averaged over the collector particle surface, assuming that the incoming droplets are uniformly distributed in space. The results extend the experimental graupel density measurements of Pflaum and Pruppacher to a wide range of graupel masses, sizes, and fallspeeds.