Multi-cavity Fluid-filled Shaking Their Aircraft System Coupled Kinetic Study

In the dissertation, with the background of flight design to a rocket with several decade sub-cavities filled with liquid, the flight ballistic properties of rocket with liquid-filled multi-containers and liquid sloshing properties in container were investigated systemically.Based on the mathematical models of liquid-filled system (liquid-rigid container), to the situations that the shape of container is cylindrical, an overview of the theoretical, numerical and experimental investigations on the basic flow and complicated flow in non-rotating liquid-filled system were presented.Main results are as follows:(1) On the basis of equivalent mechanical models for liquid sloshing in a single tank, the equivalent mechanical models for liquid sloshing in multi-tank were proposed, and the calculating formulas for forces and moments acting on flight vehicle due to liquid sloshing of multi-tank were obtained.(2) A finite element method (FEM) for calculating eigenfrequencies and damping ratios of liquid sloshing with small amplitude was proposed. Some experiments on small amplitude liquid sloshing forced by horizontal excitations for different liquid depth in a circular cylindrical tank with spherical bottom were carried out. The first order eigenfrequency and damping ratio from experiments validated the calculating results by FEM.(3) By the experiments results about attenuation process of first order lateral free sloshing in a hemisphere container for different liquid depth, it was founded primarily that the nonlinear sloshing with large amplitude shows softening behavior and the relationships between damping ratios and amplitudes are complex. Based on the experimental observations on liquid nonlinear sloshing forced by vertical excitation in a circular cylindrical tank with spherical bottom, the relationships between liquid drop ejecting and maximum exciting accelerations are given. And it was also indicated that the mechanism of liquid drop ejecting depends on excited frequencies and surface tension coefficients relying on gravitational waves and capillary waves on liquid surface.(4) The experiments on liquid sloshing excited by vertical and horizontal excitations in multi-tank were performed. The phenomena about super-harmonic oscillation, resonant mode sloshing, saddle mode sloshing, campaniform mode sloshing, liquid drop ejecting etc. were observed in vertical and horizontal excitations. In the vertical situation, if the exciting frequency is low, the amplitude of sloshing in tank on top-layer is larger than that on bottom-layer. If the exciting frequency is high, the differences among amplitudes of sloshing in any layer are slight. In the horizontal situation, the case is opposite, which is that if the exciting frequency being low, the differences among amplitudes of sloshing in any layer are not evident, otherwise if the exciting frequency being high, the amplitude of sloshing in tank on top-layer is larger than that on bottom-layer.(5) By applying the Rumjantsev's Partial Variable Theory (PVT), the mathematical models of coupling dynamics of liquid-filled flight vehicle were proposed. It was demonstrated that the behavior of flight system is mainly affected by the force and moment due to the pressure from the wall and the gravity of the liquid.Combining with the design of rocket with liquid-filled sub-cavities, the simulating models of flight ballistics were established, and simulation calculations for planning model projectiles were processed. Following conclusions were obtained. In a situation that the flight of rocket filled with small liquid mass is stable, because the attack angle and the excited amplitude to liquid within container are small, so the influences of liquid sloshing to rocket flight ballistics are also small. However, if the mass center of liquid is not coincided with that of flight vehicle, the influences of liquid gravity moment become large. When the distance between the mass center of liquid and the mass center of flight vehicle is large, the influences to rocket flight ballistics become serious, which even induce flight instability. In reverse, reducing the distance and the liquid mass, the influences to rocket flight ballistics may be decreased.