Dynamic Analysis Of Liquid Sloshing And Sloshing Suppression Design For A Tank

Liquid sloshing problems exist widely in the field of aerospace, ship and pavement transportation. For the aircraft, when taking off, landing and flying, fuel sloshing could bring adverse effect under the extrinsic excitation. On the one hand, cyclic impact load results in the fatigue failure of tank structure. On the other hand, the center of gravity (CG) may be changed due to the fuel CG transition, and the aircraft stability will be also influenced. At present, the research on liquid sloshing of aircraft mainly focuses on the structure failure, and most of the research depends on the high cost tests at home and abroad. Therefore, numerical research on fuel sloshing and sloshing suppression design of aircraft tank have much more important academic value and practical engineering significance.Firstly, continuous and incompressible fluid with free surface in a tank was described using mathematical method. Hydrodynamic N-S equations described by Lagrange method were established. Further more, hydrodynamic and dynamic boundary conditions of structural boundary and free surface were expatiated. The expression of hydrodynamic pressure was given. Elastic thin plate theory was discussed. N-S equations with SPH form were also derived. Basic conditions and processing methods of hydrodynamic simulation by SPH method were introduced. Artificial viscosity, wall boundary processing , solution of the imcompressible flow problem and some other problems were studied.Secondly, two liquid sloshing tests given abroad were numerically simulated by SPH method. With rotational sinusoidal excitation, sloshing characteristics in a prismatic liquid tank under 5 working conditions were obtained. Calculation results were compared with experiment results, perfect in agreement. The effects of liquid fill ratio, sloshing cycle and amplitude on wall pressure were investigated. With the translational acceleration excitation, liquid sloshing and impact in three dimensional rectangular containers with and without baffles were simulated. Calculation results were similar to the experiment and CFD results. With large-amplitude sloshing, welter and fragmentation of wave were simulated successfully. Reasonable and accurate SPH method lays a foundation for the study of aircraft fuel tank liquid sloshing.Thirdly, according to the type A aircraft auxiliary fuel tank and type B aircraft wing integral fuel tank, numerical simulation of tank sloshing in 5 cycles were performed on the basis of aircraft tank sloshing test. Structural stress and stress concentrated parts were obtained. The parts with maximal stress of auxiliary fuel tank have excellent agreement with the failure position in the test. Time histories of the fuel CG transition were plotted. The CG transition curves show periodicity on the motion trajectory. Analysis of structural dynamic strength and liquid CG transition could instruct the remodeling design of aircraft fuel tank.Finally, the rectangular container in chapter 3 were used, moreover, a columniform container model similar to auxiliary fuel tank was designed. Based on iSIGHT, sample points were designed using Latin designing method, the second order response surface models were also built up. Sequential quadratic programming was used to optimize the installation position and size of the tank baffles. Optimization constraint was the liquid CG, with the weight of tank baffles as optimization objective. The two optimization examples presented in this paper have guiding significance for aircraft fuel tank structural design, general design, as well as spacecraft propellant tank sloshing suppression design.