Penetration of individual microparticles into rigid barriers on collision of powder streams with them

In a number of experiments with high-velocity powder streams, ultra-deep penetration of individual microparticles into obstacles has been observed on impact of them with rigid barriers. Previous ideas about crater formation are not in a state to explain this penetration. A hypothesis is suggested and discussed for capture of microparticles by an SW front which has a finite width in real materials. From equilibrium conditions for all of the forces acting on a particle, a condition is obtained for this entrainment. A number of numerical experiments are provided which point to the competence of this hypothesis.