Fluid-solid Coupling Vibration Analysis Of Rectangular Containers

Dynamics of fluid-solid interaction,an interdisciplinary subject,research on the dynamic behavior of deformable solids under the action of fluid field and the influence upon the fluid field by the solid deformation.It is widely used in the field of aerospace,marine vessels,pressure vessels and rail transportation.The inherent characteristic of structure is obviously different from the character of structure coupling with fluid,so the study of fluid-solid coupling mechanism is a worthy subject.This paper focus on the solution of the differential equation of the rectangular thin plate structure in the case of coupling with the fluid,and then obtain the coupling vibration frequency formula and the vibration characteristic of the thin plate.Firstly,the differential equations of the coupled system are obtained by the related knowledge of fluid mechanics,elasticity and fluid-structure coupling dynamics.The method of approximate solution is adopted.The velocity potential function is implicitly displayed by the time function,and the deflection function adopts the Fourier transform form of the polynomial function.The admissible function of fluid velocity potential and plate deflection are set to satisfy with boundary conditions.The method of Fourier transform,Galerkin integral and differential transform is used to derive the coupling vibration frequency formula of the thin plate from the two-dimensional dimension.Then,the calculated result derived from coupling vibration frequency formula of the thin plate is compared with the results of the reference.The differences between the two results and the causes of the errors are analyzed On the basis of the above analysis and considering the three forms of the influence of fluid,the correction coefficient of the thickness per unit area is introduced to modify the formula to obtain the modified vibration frequency formula of the thin plate.Again,the calculated result derived from modified formula is compared with the results of the reference.The differences between the calculated result from the modified formula and the reference is significantly reduced,which proves the correctness of this method.Finally,by using the modified formula and the finite element analysis,the influence of the factors such as the aspect ratio and thickness of the plate,the depth and density of the fluid on the coupling vibration frequency are analyzed under the condition of introducing the dimensionless parameter.The method is used to analyze the improvement scheme of the fuel tank structureThe results show that for the fluid-solid coupling system of rectangular tank with rigid sidewall and flexible bottom plate,it is reliable to calculate the coupling vibration frequency of the thin plate with the modified formula.In both cases of using aluminum and steel material,the change trend of coupling frequency is basically the same.With the increase of the depth and density of fluid and the aspect ratio of plate,the fundamental frequency of the coupling vibration of plate will gradually decrease.In contrast,the frequency will gradually decrease with the increase of the thickness of plate.In the modified design of fuel tank structure,Optimizing the position of the internal baffle or increasing the number of baffles is more reasonable than increasing the thickness of the base plate.