Numerical Simulation Of Sonar Fairing Flow Noise

The mechanism of flow noise for the underwater appendage on ship is very complicated. Up to now, all the researches about the mechanics mechanism and the dissemination characteristics of flow noise have a lot of diffcult problems still.This thesis researches the flow noise for the underwater appendage on ship. Firstly, it calculates the acoustic pressure spectrum for the underwater appendage on ship which has been compared with the model test results through theoretical analysis and numerical calculation methods. Moreover, the result of comparison between the value calculated by LES/FWH hybrid method and model test value shows accordant in the low frequency proportion of the acoustic pressure spectrum while still exists defference which has been considering caused by the large eddy simulation method in the high frequency proportion of the acoustic pressure spectrum in the thesis. Secondly, it approximately calculates the surface acoustic power level distribution of the underwater appendage based on NACA fins through Lilley's broadbond noise model method. The research indicates that the surface acoustic power level of the underwater appendage is directly proportional to the inflow velocity, and is also directly proportional to the thickness and leading edge radius. The noise sources of underwater appendage based on NACA fins distribute at leading edge. These results can provide some reference for further study either. Thirdly, this thesis calculates the acoustics field of a current fairing and gives a appropriate grid number which can be accepted in this case for calculation through the research. The surface acoustics power level and the acoustics sources distribution nephogram are given in this thesis. The main acoustics source distributes on the leading edge of the fairing. The research also shows the influence of navigational speed which affects the amplitude of acoustic power level only. Some advices are also given as reference about the decreasing of flow noise during the fairing design and the disposal of sonar in the fairing.