The physical products of splashing water drops were investigated with respect to several parameters: impact velocity, drop size, surface tension, radius of curvature and roughness of the target surface, and the depth of liquid film covering the surface of the target. It is shown that the number of droplets produced by a splash increases with surface roughness, impact velocity and drop size, but decreases with an increase in liquid film depth and with a reduction in surface tension of the drop. For a given drop size, the number of splash products is proportional to the kinetic energy of the drop at impact. The size distribution of splash products is approximately log-normal; the mean size of the ejected droplets (approx. 120μm diameter) increases with drop size, surface roughness and depth of liquid film, but decreases with increasing impact velocity and with a reduction in surface tension.
Certain empirical relationships are established which permit the number of splash products, N, to be estimated in terms of the conditions of impact. One such relationship gives N=3.4 R³V²-63, where R(mm) is the radius of a water drop impacting a flat solid surface with velocity V(ms^-1). It is also shown that water drops of less than 0.75mm in radius require an impact velocity greater than their terminal velocity if they are to eject droplets.