Migration of suspended particles in plane stationary ultrasonic field

The time-averaged motion of microscopic particles in plane stationary sound fields is investigated. A generalized kinetic theory of particle migration in which the effect of particle diltusion is taken into account is formulated and the particle distributions at the rather early stage and after a sufficient sound irradiation are derived analytically from the theory. It is found that the nodal change of particle concentration of microscopic polystyrene latex dispersions is well predicted by the present theory, independently of the particle size, the sound frequency and the energy density of sound. The condition of formation of the Kundt's tube striation is also characterized theoretically.