ABSTRACT
As is known from hydrodynamics, when sound waves of large amplitude are propagated in a liquid, there appear shock waves with surfaces of discontinuity. The essence of this phenomenon is the following: different points of the wave front move with different velocities, and this leads to a deformation of the wave front in time. Points with large velocities move forward (to the crest of the wave), leaving behind them the points with smaller velocities. Finally the wave front may be bent so much that it ceases to be a single-valued function of the coordinates. Physically, such a situation is not possible. What in fact happens is that a discontinuity appears, which separates off one part of the twisted wave front. As a result all physical quantities in the wave turn out to be single-valued functions of the coordinates. The shock waves which are thus formed from sound waves, naturally have small amplitudes.
