Analysis And Control Of Flow-induced Noise In The Bow Of Underwater Vehicle

As an important weapon and equipment of national military forces,underwater vehicles are widely used in underwater detection and covert operations because of their good concealment,strong maneuverability and wide range of operations.At high speed,hydrodynamic noise is the main noise source of underwater vehicles,so effective control of hydrodynamic noise can improve the comprehensive performance of underwater vehicles.Flow-induced noise is generated by the interaction between the flow field around underwater vehicles and the wall surface,which will cause serious harm to the acoustic window structure at the bow.Due to its complex formation mechanism and numerous influencing factors,it is of great significance for the analysis and control of flow-induced noise of underwater vehicles.In this thesis,the flow induced noise of underwater vehicle bow is analyzed and controlled by statistical energy method in high frequency band,and a composite sandwich structure which can effectively control flow induced noise on the premise of ensuring strength and sound transmission is designed.In low frequency band,an active vibration control method based on admittance response of left feature vector configuration is proposed,which provides effective theoretical support for vibration and noise control of local bow structure.The main research contents are summarized as follows:1.Studied and analyzed the domestic and foreign research status of statistical energy method for noise control in high-frequency cabin,and mastered the basic theories of statistical energy method,including basic meaning,power flow equation,mode density and loss factor.The high frequency model of the bow of underwater vehicle is established to forecast the convection-induced noise and analyze the contribution of the internal cavity,which provides reference for acoustic packet noise reduction.2.The influence of the velocity and distance from the front end of the turbulent layer on the convection-induced noise was analyzed,and the performance of different structural materials in reducing the flux-induced noise with the same thickness and the analysis of sound permeability were explored.According to the damping noise reduction principle,a composite sandwich structure design including three layers and five layers was proposed.Relying on a tablet model,Through abaqus,matlab and isight,the optimal layup thickness of three-layer and five-layer composite sandwich structure is obtained.3.Select several optimal ply thicknesses,and compare the sound permeability of composite sandwich plate against single-layer composite plate respectively,and compare the noise reduction performance and sound permeability performance of three-layer composite sandwich structure and five-layer composite sandwich structure with different ply thicknesses,so as to obtain the optimal ply thickness with high permeability and low noise.Then,the acoustic package insulation capacity optimization analysis is carried out for the internal cabin of the bow of the vehicle.Five acoustic package schemes are set according to practical acoustic insulation materials,and the optimal scheme is selected through the calculation of the acoustic insulation capacity.Finally,the built-in optimization algorithm is used to optimize the thickness of the acoustic package to obtain the best scheme.4.An active vibration control method based on the left feature vector configuration of admittance response is proposed to control the fluid-induced vibration noise of the bow part structure of low-frequency underwater vehicle.Since structural vibration is related to both eigenvalues and eigenvectors,and the excitation positions of some structures are known when underwater vehicles are traveling,it is of great significance to use the relationship between left eigenvector and excitation for active vibration control,which provides important reference value for practical applications.