Effect of skew on the tonal noise characteristics of a full-scale submarine propeller

Abstract

Recently, interest in underwater propeller noise has been increasing, especially submarine propeller noise which is directly related to the survivability. The submarine propeller is operating in a strong non-uniform inflow, thereby generating unsteady loading noise, which is dominant under non-cavitating conditions. It is widely known that unsteady loading noise can be reduced using a skewed propeller, therefore, accurate modeling of non-uniform inflows is important to understand the effects of skew. In this study, the entire submarine and propeller were modeled at full scale to consider the non-uniform inflow and analyze the effect of skew on tonal noise characteristics. Numerical studies of the submarine with Case-B (Base) and Case-S (Skewed) propellers were carried out in STAR-CCM+, and each case was analyzed according to the advance speed. The results show that the thrust of a blade fluctuates significantly and causes unsteady loading noise when the blade passes through non-uniform inflow regions. The noise level of the Case-S propeller decreases by 9-10 dB from that of the Case-B propeller near the axial direction but increases at specific radiation directions. Furthermore, it was observed that the effect of the skew on the tonal noise decreased as the advance speed increased.