NONLINEAR SLOSHING OF LIQUID IN A CIRCLE CYLINDRICAL CONTAINER UNDER PITCHING EXCITATION
俯仰运动圆柱贮箱中液体的非线性晃动

In this paper, the nonlinear sloshing of liquid in a circle cylindrical tank under pitching excitation is studied analytically for the first time. Owing to the complexity of problem, it is very difficult to solve the nonlinear sloshing of liquid in a container subjected to forced pitching and (or) yawing oscillation by existing methods. Therefore, a method used to analyze this problem is presented. Firstly the nonlinear initial-boundary problem of PDE system for liquid sloshing in a container under pitching and (or) yawing excitation is established. With regard to the previous problem, variational principle and Lagrange function in the form of the volume integration of liquid pressure are obtained. Based on the variation equation and new Lagrange function proposed, nonlinear dynamic system for sloshing of liquid in a circle cylindrical container under pitching and (or) yawing excitation is derived. Subsequently, the nonlinear dynamic system gives the free surface kinematics and dynamic boundary condition. At the same time, the present method greatly reduces the work of formula derivation. Finally, the nonlinear dynamic system is solved by the multiple scale method. The dynamic characteristic of nonlinear liquid sloshing is analyzed in detail. Some kinds of motion which may appear in the liquid sloshing are discussed. Response curves and stable-unstable regions of liquid motion are determined. As to two-dimensional sloshing in a rigid, rectangular, open tank, the comparison between theoretical result by the present method and experiments shows good agreement. So, the present method is proved feasible. By means of the present method, the coupled dynamics of liquid in a tank and structure may also be investigated analytically.