Abstract:
The waveform of a single cavity volume change based on classical single cavitation dynamics model has been simulated.The instantaneous free-field acoustic pressure radiated from a pulsating monopole source can be derived by solving the acoustic wave equation in the case of a fluctuating mass source.If its density change is assumed to be negligible,the monopole pressure waveform is directly proportional to the second derivative of the cavity volume change.Based on the physical mechanism of low frequency line spectrum on propeller cavitation noise,the acoustic radiations of a great of cavitation bubbles can be represented by a single cavitation bubble during the time of propeller cavitation.A pulsating radiated acoustic pressure,which is caused by propeller rotation,is treated as a pulsatory random process with the radiated acoustic pressure waveform from a single cavity,equal iterative,random amplitude and structure of group by group.Through overlapping white Gaussian noise,the randomicity of pressure waveform of low frequency line spectrum is simulated.The transfer function expressions of radiated acoustic pressure field based broadband Lloyd-Mirror pattern are deduced,and the characteristic of transfer function is analyzed.Based on the above,the nearfield radiated acoustic pressure in deep water from a shallow pulsating monopole source is simulated.Although the model of low frequency line spectrum on propeller cavitation noise is simplified,the results are in good agreement with experiment results.