Three Nonlinearities in Physics of Acoustic Flows

Abstract

There are three types of nonlinearities in problems of acoustic flows. First, there is a nonlinear parameter in the expression for the radiation force causing the flows. Second, there is a hydrodynamic nonlinearity, which is the convective term in the equation of motion of a fluid. Third, the wave itself, which results in the flow arising, can be nonlinear. It is shown that these nonlinearities can manifest themselves independently of each other. The widespread opinion that the nonlinear term in the equations of hydrodynamics should be taken into account only for sufficiently strong acoustic waves is inaccurate. The “acceleration” of a fast flow can be carried out also by a weak wave in a large volume with a low-viscosity liquid if the action of the radiation force continues for a long time. The estimates and formulas that explain these statements quantitatively are given.