Precursor waves associated with the motion of sources of variable intensity in a stratified fluid

Abstract

When a source of variable intensity moves in a stratified fluid, several types of waves, possibly including waves that outstrip the source (precursor waves), are generated. By analyzing the expressions for the mean energy losses due to internal wave radiation per unit time it is shown that in fluids with convex wave dispersion curves up to four types of waves per mode are possible. One of these types, which vanishes under supercritical conditions, is related to the precursor waves. The angle dependence of these waves and their conditions of excitation with respect to source velocity are established.