Sinusoidal Vertical Motion Suppression and Flow Noise Calculation for a Sonobuoy

The flow noise associated with sinusoidal vertical motion of a sonobuoy restrains its working performance. In practice, a suspension system consisting of elastic suspension cable and isolation mass is adopted to isolate the hydrophone from large vertical motions of the buoy on the ocean surface. In the present study, a theoretical model of vertical motion based on the sonobuoy suspension system was proposed. The vertical motion velocity response of the hydrophone of a sonobuoy can be obtained by solving the theoretical model with Runge-Kutta algorithm. The flow noise of the hydrophone at this response motion velocity was predicted using a hybrid computational fluid dynamics (CFD)-Ffowcs Williams-Hawkings (FW-H) technique. The simulation results revealed that adding the elastic suspension cable with an appropriate elastic constant and counterweight with an appropriate mass have a good effect on reducing the flow noise caused by the sonobuoy vertical motion. The validation of this hybrid computational method used for reliable prediction of flow noise was also carried out on the basis of experimental data and empirical formula. The finds of this study can supply the deep understandings of the relationships between flow noise reduction and sonobuoy optimization.