Study On Flow Stability And Noise Reduction Characteristics Of Quasi-periodic Elastic Support Skin

Hydrodynamic noise will expose the underwater position of the underwater vehicle,and the skin laying on the surface of the underwater vehicle can effectively reduce the hydrodynamic noise.However,in the design of the skin of the current underwater vehicle,due to the failure to effectively suppress the disturbance of the convective body,the skin can not give full play to the noise reduction effect in the actual use.Therefore,it is necessary to design the skin structure and analyze its noise reduction performance.In this paper,the dynamic equation of the skin is established with the quasi periodic elastic support skin as the research object.Based on this,the characteristic equation of flow stability is derived.Through solving the equation,the reasonable value of skin structure parameters is obtained.Through two-way fluid structure coupling simulation of the skin,the suppression effect of the skin on the fluctuating pressure is verified.Through acoustic calculation,the hydrodynamic noise is reduced The solution is given,and the noise reduction characteristics of the skin are obtained by analyzing the calculation results.This paper mainly completed the following research contents:Firstly,the theoretical model of quasi periodic elastic support skin is established.Based on the stress analysis of skin,the basic form of skin dynamic equation is obtained.On this basis,the equivalent form of skin dynamic equation is obtained by transforming the equation,and the impedance function of elastic support element and fluid impedance function are determined respectively.Secondly,the flow stability of the skin is analyzed.The characteristic equation of flow stability is derived from skin dynamics.The influence of skin structure parameters on flow stability is analyzed by solving the equation,and the reasonable value of skin structure parameters is determined to complete the skin structure design.The results show that the variation of the skin’s periodic spacing,flexible wall parameters and elastic support element parameters will affect the flow stability,while the skin can maintain the flow stability only when the above structural parameters are reasonable.Then,the quasi periodic elastic support skin is simulated.Based on the platform of ANSYS Workbench 17.0,the two-way fluid structure coupling simulation of skin is carried out.By analyzing the change of pulsating pressure in the flow field and the stress and strain produced by skin,the effect of skin on pulsating pressure suppression is obtained,which also provides the necessary input conditions for the calculation of hydrodynamic noise.The results show that the skin can effectively suppress the fluctuating pressure which causes hydrodynamic noise,and the skin can produce appropriate stress and strain to consume turbulent kinetic energy.Finally,the noise reduction characteristics of quasi periodic elastic support skin are obtained.The fluctuating pressure and mesh information obtained from the two-way fluid structure coupling simulation are substituted into the acoustic analogy method and the boundary element method respectively to solve the hydrodynamic noise.Through the analysis of the calculation results,the noise reduction characteristics of the skin are obtained.The results show that the skin can reduce 10 dB and 8 dB respectively for the low-frequency noise below 1000 Hz in X and Z direction,and 5 dB for the high-frequency noise above 1000 Hz in Y direction.