Vibration And Noise Suppression Of Side Array Platform Under Fluid Excitation

Acoustic concealment is a key feature of underwater vehicles,and ensuring the concealment of underwater vehicles is a research hotspot at this stage.Hydrodynamic noise is the dominant noise at higher speeds,including flow noise and flow-induced noise.Flow noise is mainly composed of noise caused by turbulent boundary layer disturbance and wall fluctuating pressure outside the shell.On this basis,the superposition of the structural vibration noise generated by the mutual coupling between the shell and the fluid is the flow-induced noise.With the continuous improvement of speed,the contribution rate of flow-induced noise in hydrodynamic noise is increasing.Therefore,this paper conducts a full study on flow-induced noise based on underwater cylindrical shell model.Firstly,the current research on convective noise and flow-induced noise is summarized in this paper.By comparing the values and simulation solutions of the SUBOFF submarine model and the‘ big blue and white fish ’model test in the United States,the feasibility of using the steady flow field as the basis and the large eddy simulation method to solve the flow field is verified.The accuracy of obtaining flow field information by bidirectional fluid-solid coupling is verified by comparing the vibration displacement,pressure and flow-induced noise of the shell.Secondly,the flow noise is calculated by the boundary element method,and the acoustic analysis of the flow-induced noise based on the two-way fluid-solid coupling is carried out.By comparing the sound pressure changes of flow noise and flow-induced noise in X,Y and Z directions,it can be concluded that the value of flow-induced noise is greater than that of flow noise at the same frequency.Both of them will increase with the distance,and the sound pressure value will decrease due to the dissipation of energy,in which the attenuation rate in the near field is higher than that in the far field.Thirdly,the main factors affecting the flow-induced noise are analyzed.At different distances,the sound pressure values of flow-induced noise under three different conditions of incoming flow velocity,shell material characteristics and shell thickness are compared.The results show that the flow-induced noise will increase with the increase of inflow velocity.Under the condition of changing shell thickness and material,the flow-induced noise value will be affected by changing the inherent properties such as shell stiffness.Finally,based on the simulation,the drag experiment is designed to verify that the two-way fluid-solid coupling can more accurately obtain the real underwater acoustic environment,and the appropriate vibration and noise reduction method can effectively suppress the flow-induced noise.