Study On Vibration And Acoustic Radiation Characteristics Of Underwater Open Elastic Cavity

Hydrodynamic noise is one of the main sources of noise for underwater vehicles,and the underwater open cavity structure is one of the typical structures for generating hydrodynamic noise from underwater vehicles.Domestic and foreign scholars have been studying the vibrational acoustic radiation of open cavity structures for a long time,but most of the research is limited to simple structures such as open structures in the air.There are relatively few studies on the complex structure of underwater open elastic cavities,and there are not many results.In this paper,a simplified underwater cavity open acoustic cavity model is used as the research object,mainly using numerical simulation method.The coupled mode of underwater open elastic cavity structure,vibration and sound radiation under various excitations,opening mode and internal partition,the influence of the plate mode on the vibration sound radiation and the control measures of the radiation noise were studied.The main research contents of this paper include:1.Considering the rigidity of the cavity wall structure,a Helmholtz cavity model of the cavity is established.The effect of the opening on the cavity mode is studied.The results show that the opening will cause the Helmholtz resonance frequency in the cavity and increase the natural frequency value of the cavity mode in the opening direction.2.Considering that the cavity wall structure is elastic,the fluid in the cavity is air and seawater,and an elastic wall cavity structure is established.The interaction mechanism between fluid,elastic structure mode,acoustic cavity mode and coupled structure mode under different fluid conditions is studied.The results show that the fluid will reduce the structural modal frequency of the coupled structure.When the fluid is seawater,the coupling structure will lose some modalities.When the fluid is air,the elastic structure slightly increases the modal frequency of the acoustic cavity;when the fluid is seawater,the elastic structure greatly reduces the modal frequency of the acoustic cavity and loses some modalities.The underwater cavity elastic cavity structure is established,and the vibration and sound radiation characteristics of the structure under various excitations are studied.The effects of vibration and acoustic radiation were studied by changing the form of the opening and the form of the internal partition.Studies have shown that for the open form,the round hole is better than the square hole;for the opening position,the opening position is optimal at the center of the top surface;for the number of openings,the single hole is superior to the porous one.For the separator,the addition of the combined partition is the best,and the addition of the two separators is better than the single separator.4.Various measures are taken to control the radiation noise of the underwater open elastic structure.For the thickness of the sheet,when the thickness of the plate is increased,the peak position of the radiation sound pressure curve is shifted back but the peak sound pressure level is increased.For the sound absorbing material,as the acoustic impedance increases,the peak value of the peak of the radiated sound pressure curve decreases,but the position of the first peak point advances.For the damping material,adding a damping layer can control the radiation noise,but the thicker the damping layer,the better.As the damping material loss factor increases,the control effect is better,but the loss factor is raised to a certain critical point and then improved.The improvement in control effect is not obvious.