基于最优运输无网格法的Whipple屏超高速撞击数值模拟

Numerical simulation of Whipple shield hypervelocity impact based on optimal transportation meshfree method

Whipple屏是航天器防护空间碎片撞击的常用结构。现有的方法在模拟Whipple屏超高速撞击时均存在问题,本文采用最优运输无网格法(optimal transportation meshfree,OTM)对其进行模拟。OTM法是一种拉格朗日无网格法,其特点是运用最优运输理论对时间进行离散,采用带有位置信息的节点和带有材料信息的物质点对空间进行离散,利用局部最大熵(local maximum entropy,LME)方法得到插值函数,基于能量释放率来判断材料是否失效。本文首先用OTM法对铝球超高速撞击单层铝板进行模拟,通过与实验结果和各类SPH法的计算结果对比,验证了OTM法在超高速撞击问题上的适用性;然后采用OTM法对Whipple屏超高速撞击进行模拟,将OTM法预测的缓冲墙与后墙的损伤情况与实验结果进行对比,结果显示OTM法不仅能准确预测缓冲墙的弹孔直径,也能很好地模拟出后墙的剥落、穿透情况和碎片云的形态。

The Whipple shield is often used for protecting spacecraftfrom the impact of space debris.There are a lot of defects in the general numerical simulation methods for hypervelocity impact problems,thus this paper used OTM(optimal transportation meshfree)method to simulate the impacting process.OTM is a Lagrangian meshless method which ischaracterized by applying optimal transportation theory to discretize time,using a set of nodal-points with position information and a set of material-points with material information to discretize space,utilizing LME(local maximum entropy)approximation schemes to get interpolation functions,and simulating the failure of materials by material-point failure method related toenergy release rate.In this paper,OTM method was firstly used to simulate the impact of an aluminum ball on a single aluminum plate.The applicability of OTM method in hypervelocity impact was verified by comparing with the test results and the calculation results of other SPH methods.Then we used OTM method to simulate the hypervelocity impact of Whipple shield.The damage of the outer bumper and the spacecraft wall predicted by the OTM method was compared with the experimental results.It could be seen that the OTM method could not only predict the diameter of the bullet hole of the outer bumper,but also accurately simulate the spalling and penetration of the spacecraft wall,and the shape of the debris cloud.