Pressure Fluctuation and Flow-Induced Noise of the Fin and Rudder in a Water Tunnel

The flow field and radiated noise resulting from water flowing through a fin and rudder were analyzed in this study. A hydrodynamic experiment was conducted in a water tunnel to measure the pressure fluctuations affecting a fin and rudder, and then the experimental data and Large Eddy Simulation (LES) results were compared and analyzed. The discussion presented herein focuses on the zero angle of attack and the Reynolds number based on a maximum width of the fin and rudder ranging from 3.6 × 106 to 9.7 × 106. Furthermore, a numerical model was developed using the LES turbulence model and Lighthill’s acoustic analog theory to predict the flow-induced noise generated by the fin and rudder. The test data reveal that the pressure fluctuation decreases as frequency increases, and the average rate of decrease is obtained for frequencies up to 5.0 kHz. Additionally, as flow velocity increases, the overall sound pressure level of flow-induced noise also increases. The relationship between the sound power radiated by the fin and rudder and the flow velocity approximately follows a power law with an exponent of seven, and the noise radiated on both sides is greater than that radiated in the direction of flow. The findings presented in this paper have practical implications for designing quieter rudders and optimizing the noise performance of underwater vehicles and ships, thereby addressing concerns regarding the impact of anthropogenic noise on marine life and ecosystems.