Numerical simulations of hydrodynamic noise of an underwater vehicle

Numerical simulations of hydrodynamic noise are made based on the Large Eddy Simulation for both flow-induced noise and noise from the flow-induced vibration of shell and propeller of an underwater vehicle. All hydrodynamic noises are predicted by using Lighthill´s acoustic analogy method, and their variation characteristics along the axial and transverse directions, the radiation directivity and the sound energy are all investigated. It shows that the radiation laws of each kind of noise in the transverse direction have good symmetry about the underwater vehicle. The noise energy in the transverse direction is stronger than the axial in the transverse direction, and decreases with increasing distance deviating from the underwater vehicle. The main energy of the flow induced-noise of the shell is distributed near the wings, while others are near the middle, the propellers, and first half of the underwater vehicle, respectively. The noise energy increases with the increase of the forward speed of the vehicle. A comprehensive analysis of the hydrodynamic noise of the underwater vehicle is also made. It shows that the hydrodynamic noise induced by the shell is the major noise at low speed, and the hydrodynamic noise induced by the propellers will dominate the whole noise with the increase of speed. The total hydrodynamic noise increases with the increase of the speed and is proportional to the square of the speed.