Numerical Prediction Of Propeller Non-cavitations Noise

The sound radiation of propeller in water occupies a very important part in ship noise. When the propeller rotates in water, the structure will interact with the surrounding fluid, then, the fluctuating pressure will be generated and radiate noise outside. So, it has a great significance on propeller design and the submarine stealth performance. In the prediction of propeller’s non-cavitations noise, the key is how to calculate the fluctuating pressure caused by the interaction of structure and fluid around. This paper has analyzed the hydrodynamic performance and non-cavitations noise of propeller in uniform flow field by means of numerical simulation.Based on the fluid mechanics and acoustic analogy equation, this paper has analyzed the hydrodynamic performance and noise of propeller model DTMB P4119. The work has been finished as follows:Calculating the hydrodynamic performance of propeller, in this part, the propeller has been both analyzed in steady flow and unsteady flow. In steady flow, three turbulence models has been used to simulate four kinds of working conditions, and the thrust and torque calculated by numerical simulation has been compared with the experimental result, and the result shows that the Reliable k-ε model is closer to the experimental result. The results of steady flow are the starting conditions of unsteady flow calculation. In this part, the sliding mesh has been used to calculate the hydrodynamic performance of propeller, also, the calculating result has been compared with the experimental result and the result shows that the sliding mesh is closer to the experimental result. Then, the distribution of pressure, velocity and wake flow has been analyzed.Forecasting the non-cavitations noise of propeller, this noise consists of rotation noise and eddy noise, and the former is caused by the fluctuating pressure from the interaction of propeller with fluid around, this is low frequency discrete spectral noise, and mainly turns up within the first five order blade frequency. Firstly, the Reliable k-ε turbulence model was used to calculate the steady state. After reaching steady state, the transient state was calculated, and then switched to the sound field calculation. The numerical calculations of non-cavitations noise in0-10KHz show that the non-cavitations noise increases with the velocity raises. At the same velocity, the non-cavitations noise decreases with the distance between observation point and propeller shaft center increases. The numerical calculations of low frequency discrete spectral noise show that in the propeller shaft center plane, the overall sound pressure level increases with the increment of distance between observation points and propeller shaft center, and the maximum pressure point locates in0.7R, circumferential fluctuation is constant. In any plane of axial direction, the overall sound pressure level increases first and then decreases at the radial direction. With the increase of axial distance, the overall sound pressure in the same plane changes slowly along the radial direction, and the peak position deviates from the propeller shaft center. The overall sound pressure level increases with the distance between observation planes and propeller shaft center plane, and the maximum overall sound pressure level plane locates in the propeller shaft center plane.