Mechanism Study On The Influence Of Different Media On The Acoustic And Vibration Characteristics Of Plate And Shell Structures

Underwater vehicles and other combat equipment are important defense lines for protecting China’s marine safety.Accurately monitoring and predicting the vibration and sound radiation levels of underwater vehicles has always been a concern.At present,underwater model measurement experiments are the main way to obtain the vibration and sound radiation characteristics of underwater vehicles.However,the vibration and sound radiation experiments of underwater models in engineering are often costly and difficult.Compared to underwater experiments,conducting experiments in air is more convenient and reliable.If structural vibration and sound radiation experiments can be conducted in air medium to analyze the changes in acoustic vibration characteristics of the structure underwater,providing prior guidance for subsequent underwater model experiments,this will undoubtedly greatly reduce experimental costs and improve experimental efficiency.This article conducts a mechanistic study on the coupling effect of medium on structural vibration and sound,and obtains the variation law of the influence of medium on structural sound vibration characteristics.It also discusses the possibility of using structure in air testing to replace or partially replace underwater testing.Firstly,this article takes simple typical structures such as rectangular plates and finite length cylindrical shells as research objects,and takes the surface mean square vibration velocity and radiated sound power of rectangular plates and cylindrical shells as characterization parameters.The vibration and sound radiation characteristics of rectangular plates and cylindrical shell structures in air and water media are discussed in detail.Secondly,based on the research on the vibration and sound radiation of rectangular plates and cylindrical shells in the air,this paper further conducts research on the vibration and sound radiation mechanisms and laws of underwater rectangular plates and cylindrical shells,and derives expressions for the modal added mass and radiation sound resistance of rectangular plates and cylindrical shells in water.Taking advantage of the characteristic that the main mode shapes of rectangular plates and cylindrical shells do not change much in different media,the wet mode shapes are replaced by the dry mode shapes of rectangular plates and cylindrical shells.Based on the modal superposition principle,a method to modify the formulas of rectangular plates and cylindrical shells in air by using modal added mass and radiated acoustic damping is proposed.And the feasibility of this correction method in predicting the underwater vibration response and acoustic radiation characteristics of rectangular plate and cylindrical shell structures was verified through specific examples.At the same time,this article also explores the consistency of the effects of boundary conditions,excitation positions,and plate thickness on the variation of acoustic and vibration characteristics of rectangular plates and cylindrical shells in water and air.Finally,experimental studies were conducted under different media conditions to measure the surface mean square vibration velocity and radiated sound power of rectangular plates and cylindrical shells.The experiment analyzed the influence of medium on the acoustic and vibration characteristics of rectangular plate and cylindrical shell structures.The experimental and simulation results indicate that due to the influence of the medium,the mean square vibration velocity and the same order resonance frequency of the radiated sound power of rectangular plates and cylindrical shells in water are significantly reduced compared to those in air.Within the same frequency band,the resonance peaks of rectangular plates and cylindrical shells in aqueous media are more dense.