Numerical study on the flow-induced noise from waterjet-propelled ship regarding a flexible boundary

Abstract

In hydroacoustics, it is generally acknowledged that a half-space is bounded by a flexible boundary with non-constant reflection coefficients. However, limited research has focused on the impact of the flexible boundary on noise characteristics. In this paper, a hybrid method combining the unsteady Reynolds-averaged Navier-Stokes (URANS) equations with the Ffowcs-Williams–Hawkings (FW–H) equation is presented. Firstly, the hybrid method coupled with the mirror source method (MS method) is applied to predict noise in a half-space with a rigid boundary for validation. Secondly, the proposed method is extended to predict the underwater noise generated by a medium-speed, mono-hull ship. Specifically, the differences between the noise fields in a half-space and free-space are considered and investigated comprehensively. The results reveal that: (1) the hybrid method performs well in predicting the overall noise induced by complex-shaped configurations in a half-space bounded by different boundaries, and (2) the half-space boundary can influence the noise field due to constructive\\destructive interferences. Additionally, (3) the quadrupole noise generated in the non-uniform wake of a waterjet-propelled ship should be considered. The proposed method has provided an efficient approach to predict the flow-induced noise radiated from a waterjet-propelled ship regarding a flexible boundary.