The Research On Experimental Design And Measuring Methods For Underwater Flow Noise Of Spheres

Flow noise is an important part of total radiated noise for high-speed underwater vehicles. The study on mechanism and characteristics of flow noise would lay the foundation for noise reduction measures and acoustic optimization design in the future, which is of great significance to improving the acoustic stealth performance of underwater vehicles.This paper takes flow noise and experimental methods of spheres as the research object. First of all, a reasonable experiment scheme and measuring method of spheres flow noise is designed and be used to measure the flow noise accurately; Then a wavelet threshold de-noising method based on CEEMD(Complete Ensemble Empirical Mode Decomposition) is proposed to remove the interference of the environment noise signal to the flow noise. The method is applied to deal with a simulative signal and the results proved its feasibility and superiority; Velocity measured by experimental methods are compared with theoretical calculation ones to obtain the motion of spheres; In view of the real-time measurement of flow noise signal, time pass characteristic and frequency spectrum characteristics of flow noise and the effect of factors such as velocity and Reynolds number on flow noise are analyzed; Finally, numerical simulation is performed using LES(Large Eddy Simulation) combined with FW-H(The Ffowcs Williams and Hawkings). Flow noise mechanism and spectrum characteristics of spheres is Studied. The results show that the frequency of flow noise mainly concentrates in the low frequency. In the experimental measuring range, the sound pressure level increases with the increase of velocity and Reynolds number. Sound pressure level of the sphere has directivity.This paper carries out a new experimental scheme of flow noise measuring on the lake, through which the speed and flow noise of spheres could be measured accurately. The flow noise characteristics of spheres are researched with signal processing and numerical simulation technology. This work would provide a reference for theoretical research and simulation calculation of flow noise, and it would provide a basis for further optimization on flow noise prediction method as well.