Acoustic radiation from a finite-length shell with substructures subjected to an impulsive load

A method is presented to obtain the impulsive response and the acoustic radiation of submerged shells of finite length. Solutions in the frequency domain are first evaluated by a modal based method and converted to the time domain using a fast Fourier transform technique. Numerical examples are presented for a cylindrical shell of finite length with endcaps, with and without bulkheads. The method is validated by comparing surface pressure response of the empty shell with that of an infinite, fluidloaded shell. It is demonstrated that the near-field pressure disturbances arise from elastic waves propagating on the shell and from the direct radiation from the driving force. The amount of energy input to the system by the driving force and the energy radiated to the far-field are calculated. Results show that most of the energy is dissipated in the shell by damping. It is also shown that shells containing bulkheads can radiate more energy than empty shells because the bulkheads generate supersonic, radiating flexural waves.