Study Of Acousto-vibration Coupling Characteristics Of Elastic Open Cavities

When the underwater vehicle is sailing in medium and high speed conditions,the open hole on the surface of the hull will lead to shear oscillation of the fluid boundary layer.When the oscillation frequency coincides with the resonant frequency of the hole cavity,it will produce strong line spectrum noise,which seriously affects its stealth performance.At present,the research on the mechanism and law of low-frequency line spectrum noise of the flow-excited hole cavity is still immature,and there are many difficulties to overcome in the establishment of mathematical and physical models as well as numerical simulation calculations.To address this engineering research background,this paper takes the submerged simple plate cavity model and the enclosure structure as the object respectively,and initially studies the vibration sound radiation problem of the point source excitation plate cavity coupling system,and carries out the circulating water tank flow-excited plate cavity test to verify the calculation conclusion,and based on the test results to analyze the sound radiation law of the flow-excited plate cavity structure,and then provides the underwater cavity structure flow-excited coupling noise control research.The experimental results were used to analyze and summarize the sound radiation law of the flow-excited plate cavity structure.Firstly,the improved Fourier series is used as the formal solution of rectangular plate vibration and cavity acoustic pressure,and the acoustic-vibration coupling equations of a typical plate cavity coupled system are derived analytically by using the Ritz method of the principle of minimum action,and the correctness of the simple model established in this paper is verified by references.The literature comparison shows that the improved Fourier series method Ritz method established in this paper has high computational accuracy and can be used to analyze the simple plate cavity pore-flow acousto-vibration coupled system by literature comparison.Then,for the complex elastic hole-slab-cavity system,the numerical model of acoustic radiation of the coupled system is established by using Virtual.Lab acoustic software with an idealized typical rectangular cavity and a typical open enclosure in engineering.The mesh data generated in Abaqus is imported into the acoustic software for modal calculation and modal characteristics analysis;meanwhile,the influence law study is carried out to summarize the influence law of cavity parameters,opening parameters and excitation source characteristics on the acoustic radiation characteristics.The main findings show that: the elasticity of the cavity wall of the plate cavity coupling system affects the resonant frequency of the plate cavity coupling system,the thinner the elastic plate,the lower the stiffness,the lower the resonant frequency of the coupling system;the damping of the cavity wall plate plays a greater role in modulating the amplitude of the resonant peak of the radiation noise of the coupling system,the greater the damping and the higher the frequency,the stronger the acoustic radiation suppression;the number of elastic parts in the enclosure structure is large,making the enclosure The resonance characteristics are more complex,and the contribution of the elastic plate and cavity to the resonant acoustic radiation is also difficult to analyze,and its excited acoustic radiation reflects the complex structural effects.Finally,in order to verify the low-frequency line spectrum characteristic law of a typical simplified open-hole plate cavity coupled system,a typical rectangular plate cavity system test model is designed and a water tank test is conducted in this paper.The modal characteristics and acoustic response law under the excitation of point source are studied,and compared with the numerical calculation results,the plate cavity acoustic-vibration coupling response characteristics have a good agreement at the low-order resonance peak,which verifies the accuracy of the numerical model.In order to further verify the low-frequency line spectrum characteristic law of the flow-excited plate cavity coupled system,the noise characteristics under the flow-excited condition were measured in the circulating water tank.The calculated results under different working conditions were statistically analyzed to analyze the effects of different factors on the acoustic radiation.The results show that: the cavity depth and the elasticity of the cavity wall affect the resonance characteristics of the plate cavity coupled system;the deeper the cavity and the thicker the elastic plate,the lower the resonance frequency;the shape of the cavity opening has little effect on the resonance frequency of the cavity,but has an effect on the shear oscillation,and the first-order shear oscillation frequency of the circular opening is slightly higher than that of the rectangular opening condition.