航天器贮箱内液体大幅晃动动力学分析

Dynamic analysis of large-scale amplitude liquid sloshing in the spacecraft

当航天器进行姿态和轨道机动时,有可能激发出贮箱内液体的大幅晃动,甚至出现液面破碎现象,此时等效力学模型方法已不适用.本文基于光滑粒子流体动力学(Smoothed Particle Hydrodynamics, SPH)基本理论,提出了基于质点系动量定理和动量矩定理的液体大幅晃动产生的作用力及力矩的求解方法,该方法可以精确地计算出液体对于航天器的晃动力和晃动力矩,避免了压力场的计算误差影响.此外,针对传统计算流体力学(Computa-tional Fluid Dynamics, CFD)方法计算效率低的问题,讨论了方法中粒子初始间距选取对于晃动力和晃动力矩计算精度的影响,在不降低计算精度的前提下通过加大粒子初始间距显著提高了计算效率,使得将其嵌入控制系统闭环仿真成为可能.最后,通过与传统CFD求解器计算结果的对比验证了所提出算法的有效性.

With the development of space technology,functionalities and life span of the spacecraft are increasing,leading to requirement of a greater proportion of fuels.Liquid sloshing in fuel tanks has more unavoidable effect on the spacecraft. During the attitude and orbital maneuvering of the spacecraft,large-scale amplitude liquid sloshing can be excited with liquid merging and splitting.Generally,theoretical,experimental and numerical methods can be used to predict the dynamics of liquid sloshing.However,most theoretical formulas,like the equivalent mechanical model methods,are only valid for liquid sloshing with small amplitude in simple geometrical tanks.Meanwhile,experimental results are difficult to obtain under a low gravity environment and the accurate measurement of nonlinear liquid sloshing is also a challenge.In most actual simulations,numerical simulation are required.In this paper,based on the smoothed particle hydrodynamics (SPH)method which is a Lagrangian mesh-less method,the linear and angular momentum theorem of the particles system are adopted to calculate the force and moment exerted by liquid against the spacecraft accurately, which avoids the accuracy loss of the pressure field.Moreover,aimed at the low computational efficiency of the common computational fluid dynamics (CFD)method,the impact of particle initial spacing on the accuracy of sloshing force and moment calculated is discussed and enough accuracy of global loads can be guaranteed with fewer particles,which greatly improves the computational efficiency.The time-efficiency of the SPH solver is adequate for embedding into a whole-spacecraft simulation system.Finally,in order to verify the validity of the method,results from SPH method are compared with those obtained by a traditional CFD solver for a 3D liquid sloshing case.