Numerical prediction of blade frequency noise of cavitating propeller

The blade frequency noise of a cavitating propeller in a uniform flow is analyzed in the time domain. The unsteady loading (of a dipole source) and the sheet cavity volume (of a monopole source) on the propeller surface are calculated by a potential-based surface panel method. Then the time-dependent pressure and the cavity volume data are used as the input for the Fowcs Williams-Hawkings formulation to predict the acoustics pressure. The integration of the noise source is performed over the true blade surface rather than the ideal blade surface without thickness. The noise characteristics of the cavitating propeller are discussed. With the sheet cavitation, the thickness (cavitation) noise is larger than the loading noise and is the dominant noise source. The noise directivity is not as clear as that of the noise under a non-cavitation condition. The cavitation noise is attenuated more slowly than the non-cavitation noise.