Spectrum asymptotics of high-frequency acoustic emission generated by surface explosion

The problem of high-frequency acoustic emission generated by an underwater explosion at the free surface of inviscid liquid is considered. Flow is ass umed to be irrotational that allows an approximate equation of motion for t he boundary of expanding breakdown to be constructed in analogy to the Rayl eigh equation for a spherical bubble. The surface of the cavity (having the "bowl"-like form) is replaced by the circular cylinder whose height is equ al to its diameter. The simple solution is obtained if the adiabatic expone nt is taken equal to 1.2. It is shown that, in the first approximation, the spectral density of an acoustic energy emitted by surface explosion varies as the minus 1.1 power of the frequency and decreases approximately by 3.3 decibels per octave. Such slow decrease of the spectral density versus the frequency is the consequence of accepted assumption about the existence of potential flow after an energy deposition. (C) 2001 American Institute of Physics.