Study On Liquid Sloshing Simulation And Rigid-Fluid Coupling Dynamics

Liquid-filled spacecraft will implement many commands, such as large-scale or-bit maneuver, a wide-angle attitude control during the mission. And on-board liquidsloshing will bring distinct in?uence to the accuracy of the instructions and the stabilityof the whole system. The rich theoretical results have been achieved from the study onliquid sloshing during these years. However, the theoretical results almost are stemmedfrom the simplified models, and the experiments cost are expensive. This paper adoptsfinite element method in the numerical simulation of the ?uid sloshing in tanks withvarious shapes, and studies the spacecraft as a rigid-?uid interaction coupled system,where the liquid-filled spacecraft is a rigid tank and the liquid is viscous.Firstly, the ALE finite element method is applied to model the free surface slosh-ing of viscous ?uid. Equal-order interpolation functions are used to discrete the finiteelement space. The Crank-Nicolson, a second order accuracy discrete method, is usedas the time discretion method. A stabilized fractional-step method is imposed to re-duce the in?uence of the pressure results driven by the improved discrete accuracy.This calculation procedure enhances the discrete precision of convection and viscousterms, and improves the velocity results. The pressure iteration procedure is chose toensure the incompressible constraint of ?uid, and it can also improve the computationale?ciency. Numerical experiments indicate that this method is very stable and can beused to simulate the ?uid sloshing in a long time. Moreover, this method has smallernumerical damping than other methods.Secondly, the moving mesh technology is studied under ALE description. Com-bined with the numerical method above, the sloshing in the tank with a variety ofcurved walls is completed. Defined the nodal velocity on the moving interface of theALE mesh as a product of a scalar and a shape vector, the kinematical boundary con-ditions on the free surface is modified to increase the freedom of the movements of thegrid on free interface. Then the interior nodes'velocities are smoothed by a Laplace technique. Numerical experiments indicate that this moving grid method does not af-fect the results of the sloshing, and can extend the ALE finite element method to theinterior ?ow computations with non-straight boundary. It is utility to simulation slosh-ing in the spacecraft tanks.Finally, the model of rigid-liquid coupled system in which liquid is viscous isestablished by using the Jourdain principle, the stagger algorithem is used in the inte-gral calculation of interaction system. The features of this mathematical model is thatit regards the liquid-filled system's response as the research object, the in?uences tothe system dynamics including the mass distribution, the inertia moment, the sloshingforce, sloshing torque and others, which are brought by ?uid sloshing, are recordedreal-time during the calculation. Numerical experiments indicate that the response ofthe liquid-filled system is strongest near the resonance frequency of the liquid itself.The characteristics of the nonlinear response exist under this frequency.