Prediction method of low-order blade frequency noise of non-cavitation propeller in time domain

In order to study the characteristics and prediction method of low-order blade frequency noise of a non-cavitation propeller, the velocity potential-based surface panel method and the noise analysis method in a time domain were adopted. The unsteady loading (dipole source) on the blade surface was calculated by a surface panel method. Then the time-dependent pressure data were used as the input for the Ffowcs Williams-Hawkings formulation to predict the acoustic pressure induced by the propeller. The integration of the noise source was performed over the true blade surface rather than the arc blade surface. The distance between the noise source and observation point was not approximated and the effect of the propeller hub was considered. Through comparison and analysis of computation results, it was shown that the sound pressure level (SPL) caused by the blade thickness and hub is very small and can be ignored. The 2nd order higher order blade frequency SPL is obviously lower than the 1st order blade frequency SPL. The 1st order blade frequency SPL is the highest in the direction of the propeller axis and lowest in the direction of the propeller disc.