Research On Hydrodynamic Self-Noise Prediction And Noise Reduction Of Sonar With Coating Layer On Boardside

As hydrodynamic noise is the main component of sonar self-noise at medium and high speed,it is of great significance to forecast sonar hydrodynamic self-noise accurately and put forward effective control method for enhancing submarine combat capability.Different from the placement of traditional sonar array,broadside conformal sonar array generally can be reduced to a space plane array coated with compliant coating layer,and the prediction and control of hydrodynamic noise of this model is studied in this paper.Several existing turbulence boundary layer(TBL)models are firstly summarized and Corcos model is selected as the excitation source of the conformal sonar structure.The prediction model of hydrodynamic noise of uniform coating layer is established by transfer matrix method and noise reduction is studied.Combined with discrete stratification method and transfer matrix method,the prediction method of hydrodynamic noise of functionally gradient coating layer is proposed and some factors that may affect noise reduction are discussed.The main aspects of this paper are studied as follow:(1)The hydrodynamic noise prediction model of uniform coating layer is established by numerical integration method and transfer matrix method.The filtering characteristics and the reduction effect of finite hydrophone,array and compliant coating layer on turbulent pulsating pressure are analyzed.(2)The hydrodynamic noise prediction method of functionally gradient coating layer is proposed by using discrete layer method and transfer matrix method and the relationship between the convergence of transfer function and the thickness of layer element is analyzed,and the results in this paper are compared with those in the existing literature to verify the effectiveness of the prediction method.(3)According to four classical kinds of functionally graded materials with linear,parabolic,power function and exponential distribution characteristics,the hydrodynamic noise prediction of functionally graded coating layer is carried out by using the prediction method proposed in this paper,and the influence of positive or negative gradient and distribution characteristics on noise reduction are explored.