Wind-tunnel measurements of restitution coefficients and ejection number of snow particles in drifting snow: Determination of splash functions

Wind-tunnel experiments of drifting snow were carried out and splash functions were formulated to describe probability distributions of vertical restitution coefficient, horizontal restitution coefficient and ejection number when a natural snow particle collided at a natural snow surface. The following results were obtained: (1) The vertical restitution coefficient was usually larger than unity and decreased sharply with impact angle. At smaller impact angles around 5 degrees the vertical restitution coefficient exceeded a magnitude of ten. (2) The horizontal restitution coefficient, ranging from -1 to 1.5, decreased with impact velocity, but was not clearly dependent on impact angle. (3) The ejection number amounted to five per impact and increased with impact velocity. (4) Three splash functions to express the probability distributions of the vertical restitution coefficient, horizontal restitution coefficient and ejection number were formulated, which will be used in future computer simulations of the snow drifting process.