THE INFLUENCE OF THE SQUEEZE FILM ON PARTICLE IMPACT VELOCITIES IN EROSION

The results of a study of the cushioning effect of the fluid between an approaching solid particle and a planar surface are reported. Solutions are obtained for the equations that describe the motion of the fluid the fluid from between the impinging particle and the target can be of sufficient magnitude markedly to the fluid from between the impinging particle and the target can be of sufficient magnitude markedly to reduce the impact velocity below the value predicted by the potential flow solution. Acriterion for the asses- sment of the effect, expressed in terms of the particle Reynolds number and the particle and fluid densities, is presented. Significant retardation immediately prior to impact is found for all particles and approach velo- cities in liquid-solid erosion, but the effect is insignificant in gas-solid particle erosion. The predicted func- tional form of the results is confirmed by experimentally determined values of impact velocity of spherical glass and steel particles suspended in various liquids deduced from examination of crater sizes.