Mechanism Of Low-frequency Large-amplitude Gravity Waves In Coupled Liquid And Cylindrical Elastic Shell System

In the recent years, nonlinear science is the important research project in domestic and international academic. As far as the liquid-solid coupled system which lies in engineering structure widely, the nonlinear factor in the system is not be ignored. It is of great value to study the nonlinear vibration of the liquid-solid coupled system.The paper is on coupled liquid and elastic shell system. According to the nonlinear vibration theory, a multiple-degree-of-freedom system nonlinear equations is constructed. Through numerical and analytic computation to the equations, we can discover that low frequency and large amplitude gravity waves can be generated by the big enough external excitation which has the frequency which about equals the sum of the excitation frequency and the shell's inherent frequency. And so the phenomenon is explained very well .Theoretical analysis is also consistent with numerical computation.1. Based on the experimental phenomenon that the low-frequency and large-amplitude gravity waves may be generated by the high-frequency external excitation in the liquid-elastic shell coupled system, according as the boundary conditions at the fluid-structure interface, a set of nonlinear equations for the multi-degree of freedom system is constructed with the use of the knowledge of hydromechanics and elasticity.2. The numerical computation is carried out by means of the Runge-Kutta method. The time history curves and frequency spectrum curves are obtained, and amplitude-frequency characteristic curves are obtained by changing the amplitude and frequency of the exciting force. Sequentially analyze the dynamical character of the liquid-elastic shell coupled system.3. The theoretical analysis is carried out by the means of averaging method. A set of nonlinear differential equations for the two-degree of freedom system is solved. According to the steady state solution of the first order approximation obtained, the relationship between the amplitude and the frequency of the external excitation and the response of the revolving gravity waves is established, which makes the vibration mechanism more clear. The results show good agreement with the numerical results.4. The modes of cylindrical container with a height and free surface of fluid are calculated with finite element software ANSYS on the basis of the fluid—solid...