Research On Vibration Prediction And Similarity Of Composite Plates Under The Action Of Turbulent Boundary Layer

Acoustic radiation from structural vibration under the excitation of turbulent boundary layer is an important part of submarine hydrodynamic noise.Composite plate structure is more and more widely used in submarine structure due to its advantages of high specific strength,high specific rigidity,and strong designability.This paper studies the underwater flow-induced vibration of two types of composite material panels: composite material laminated panels and composite material sandwich panels.In the research and design stage of convection-induced structural vibration and acoustic radiation,it is often necessary to rely on the results of model tests.Therefore,the study of a set of vibration response prediction and similar conversion methods for composite rectangular plates under the excitation of turbulent boundary layer has great engineering significance and application value.First,a similar conversion method for the flow-induced vibration response of a homogeneous single-layer flat plate in air is established.Based on the equation analysis method,three conditions that must be met for the flat plate model in air to be similar to the prototype are studied.A similar conversion method from the model test results to the prototype is also given.For fluid-loaded plates,two similar conditions are added on the basis of similar conditions in air,and a similar conversion method for the response of plate fluid-induced vibration in different fluid media is established.The conversion results show that this method can realize the conversion between the responses of plates of different sizes and different materials under the excitation of the turbulent boundary layer of the same medium.This method can be used to realize the theoretical conversion for the plate flow induced response of different external flow field media.Secondly,the calculation and similar conversion method of flow-induced vibration of composite laminates are studied.A simplified third-order shear deformation theory is introduced to describe its displacement field.Applying the variational principle to obtain the control equation of the composite laminate,combining the acoustic wave equation and continuity conditions to derive the single-frequency response function of the composite laminate under external flow field load,and combining the wall pressure cross-spectrum model to establish the flow-induced vibration self-power of the laminate Spectrum calculation formula.The applicability of the similarity conversion method in this paper is verified on composite laminates with the same material and completely similar geometry.Studies have shown that: a proper ply angle can reduce the flow-induced vibration response;the use of slender panels is beneficial to reduce the magnitude of the flow-induced vibration response.Finally,the calculation of flow-induced vibration of soft sandwich panels and similar conversion methods are studied.The first-order shear deformation theory is introduced,and the Layerwise model is constructed to describe the displacement field in combination with the continuous condition of the inter-layer displacement.The single-frequency response function of the sandwich panel is deduced,combined with the turbulent wall pulsating pressure crosspower spectrum model,and the calculation formula of the self-power spectrum of the sandwich panel’s flow-induced vibration is established.In the case that the far-field flow rate is set by itself,the applicability of the similar conversion method in this paper on sandwich panels with the same material and completely similar geometry is verified.Research shows that panel stiffness and soft core loss factor are important parameters that affect the magnitude of low-frequency and medium-high frequency flow-induced vibration of sandwich panels,respectively.The placement and thickness of the damping layer have little effect on the flowinduced response.