Theoretical And Experimental Research Of Underwater Noise Reduction Prediction Based On Wave Superposition Method

Radiation noise is an important index to measure the operational performance andviability of submarine, it is the main detection target of enemy acoustic weapons, and itdirectly affects the submarine acoustic stealth performance, so it is important for noiseprediction for underwater typical structures of similar power cabin submarine. Acousticcovering layer in the submarine surface is main means of noise reduction, the theoreticalprediction and test of the noise reduction effect is extremely important, so the paper works onthe underwater noise prediction research of underwater typical structures. But the study ofnoise prediction has some technical difficulties, including the way to obtain validmeasurement data; the way to reduce the number of measuring hydrophone;the way to reducemeasuring cost; the way to estimate the acoustic radiation of other conditions and reducingthe number of engineering based on data of underwater adhesions sound field and noadhesions sound field. Considering problems of the existing noise prediction of underwaterstructure, this paper worked on the following research:The paper introduces the background of the wave superposition method, and states thedynamic research at home and abroad on the acoustic field prediction, near field acousticholography, noise source identification of the dynamic research, and analyses the researchmethod of noise reduction mechanism and noise prediction structure acoustic covering layerunder water, and discusses the advantages and disadvantages of each method, and points outthe technical difficulties in applying the wave superposition method to the structural acousticunderwater noise prediction, according to the research needs in this area, the main contents ofthe thesis are determined.The paper works on noise prediction theory based on wave superposition method underthe condition of free field, namely predicting sound field of underwater structure coveredbased on underwater structure not covered. Firstly, the paper explains the principle of wavesuperposition method based on measurement of vibration velocity and sound pressure, andanalysis the effect of regularization filter on calculation accuracy of the wave superpositionmethod, the paper discusses the viscoelastic material impedance transfer principle andprocessing method coupled with the structure of the interface; taking pulsating sphere, singlepoint excitation spherical sound radiation as an example, the paper introduces the complexantero-posterior diameter, and the paper respectively verifies the significance of the wavesuperposition method based on measurement of vibration velocity and sound pressure; the paper discusses the factors that influence the accuracy of sound field, the initial conditions ofsurface pressure measurement based on ANSYS finite element and boundary elementSYSNOISE software, the paper studies the noise reduction effect of radial finite singleunderwater incentive simply supported cylindrical shell paste the uniform viscoelasticmaterial.The paper works on noise reduction prediction theory based on wave superpositionmethod with the half free field, namely, predicting the sound field of underwater structurecovered by the sound field of underwater structure not covered. The paper firstly works onwave superposition method of the half free field based on sound pressure measurement, thecalculation method of reflection coefficient between virtual source point and sound point, themethod of virtual image source calculation and software measurement are given under ahalf-free field condition. Under numerical simulation of the half-free field condition, the noisereduction effect of spherical shell and cylindrical shell with simply supported edges pastesingle radial excitation are calculated, and the simulation results are compared with thenumerical result of software and calculation of free field results.The paper works on backward noise prediction theory under the adhesive layer ofunderwater structure, and it means predicts uncovered sound field using underwater structurewith viscoelastic coating sound field. Firstly, the paper states backward noise reductionprediction theory based on wave superposition method of pressure measurement underunderwater structure has pasted the viscoelastic material. Secondly, the paper works onparametric setting method of underwater structure sound field based on the paste ofviscoelastic materials of finite element and boundary element software, the softwarecalculates surface pressure of viscoelastic material spherical shell and cylindrical shell offinite length, and the result is considered as the initial condition, wave superposition methodare used and combined with viscoelastic material impedance transfer and interfacial couplingtheory, the radiation pressure of spherical shell and cylindrical shell with viscoelastic layer ofpaste are calculated, and thus the effect of reducing the underwater structure adhesiveviscoelastic layer is predicted.The paper works on noise prediction theory of structure that is pasted by underwatercomposite structure, considering the viscoelastic materials with hollow composite structure,and it is in a small perforation ratio, structure rule and uniform distribution, Using theacoustic parameters equivalent method, the wave superposition method is introduced, thepaper works on the noise reduction effect of underwater structure; considering the nodestructure under water for a viscoelastic material, the paper uses acoustic impedance matching method to optimize the external loss circuit parameters, and then combined with thepiezoelectric impedance transfer principle and wave superposition method, the noisereduction effect of underwater structure is theoretical predicted.Finally, the paper works on noise reduction coverage of underwater structure pasteviscoelastic prediction experiments based on the wave superposition method, consider usingwave superposition method, combined with viscoelastic material impedance transfer andinterfacial coupling theory, by measuring the surface sound pressure through a workingunderwater structure and then predict sound pressure of another condition of the field. Thepaper works on the single condition forecast on the noise reduction of underwater doublecylindrical shell sticking visco-elastic covering, and then the sound pressure and noiseprediction effect are compared with the experimental results. Consider viscoelastic smallaperture cavity has a cycle, rules for internal coverage, the paper respectively works onimpedance transfer and interface coupling based on the equivalent parameter method andvariable cross-section waveguide theory, the forecast method for cylindrical shell workingforward and reverse are verified. By the analysis of error comparison, the wave superpositionmethod that is applied to elastic underwater structure adhesive cover noise reductionprediction is effectively evaluated, the conclusion is applied in the application of engineeringto provide effective technical support.