The problem of wave momentum, radiation pressure and other quantities in the case of plane motions of an ideal gas

Small vibrations and waves of an ideal fluid gas (a liquid or gas) are cons idered in the quadratic approximation. Actual values of the momentum densit y and the pressure and also their averaged values are obtained in a number of specific characteristic problems. It is shown that the momentum of an is olated wave with a mean density equal to the density of the unperturbed med ium, and the radiation pressure are due to non-linearity of the system of e quations, and that this wave has no momentum if its profile remains unchang ed during its motion. The latter assertion is also true for finite-amplitud e waves. (C) 1999 Elsevier Science Ltd. All rights reserved.