结构物入水冲击动力学问题的DSPH计算方法和试验研究

This proposal comes from the complex event of crash landings on water in modern aerospace vehicles. The objective of this project is to setup a platform to evaluate the crashworthy concepts prior to expensive testing programs, and the global research focus is on developing efficient simulation tools, particularly using the DSPH (Discontinuous Smoothing Particle Hydrodynamic) method. Through numerical modelling with experimental testing, a better understanding of the dynamics behavior of the event can be gained and thus lead to the development of efficient computational tools...The aim of the computational tool is to extend our self-developed discontinous SPH （DSPH）codes to describe the fluid-structure interaction,which has been previously applied in presenting the interfaces between two solid materials under imapct loading. The numerical accuracy and the stability for DSPH method in sloving the fluid solid coupling interface would be the main issues. The effect of the DSPH code on simulating the dynamic response of rigid wedges will be validated by the corresponding water entry tests. Then several scaled models of a typical shell structure will be investigated by the DSPH computational tool to analysis the dynamic similarities among them. ..Experiments will be conducted on the rigid wedges and different scaled models with varying impact factors, such as the mass, the geometry, the impact velocity， etc. The high-speed video camera, the thin film PVDF,the accelaration sensor, the laser and the strain gage will be equipped to record the dynamic characteristics of the water entry event. All these data would be used to validate our simulation results to develop the DSPH method.

本文以大型飞机水上迫降、航天飞行器水上回收等重大工程问题为研究背景，拟建立一套较完整的以DSPH计算为主、试验为辅的分析方法，研究结构物入水的冲击动力学响应规律，并给出冲击过程中结构物减速、入水砰击力、结构物表面压力分布等力学参数，为结构物入水的安全性评估提供理论与技术支撑。拟开展三方面的研究工作：（1）在课题组针对弹靶侵彻问题中固/固不连续界面的DSPH方法研究和自编分析软件的基础上，将其推广应用到流固耦合界面问题，着力提高计算的精度和稳定性；（2）建立结构物入水试验测试系统，开展楔形体入水的试验研究，验证算法及其软件的有效性；（3）开展不同尺寸缩比模型入水冲击动响应规律的数值计算研究，结合模型入水试验，探索壳体结构入水冲击动力学缩比模型的相似性问题。

项目针对大型飞机水上迫降、航天飞行器水上回收等重大工程问题的研究背景，开展了结构物入水的试验和数值仿真计算方法研究，考察了SPH算法研究固-液-气多介质相互作用的计算能力，提出了固液界面考虑界面力的DSPH算法。.取得研究成果主要为：（1）试验方面，设计构建了水平和垂直两套结构物入水试验测试平台，能够完成结构物入水过程加速度和表面压力的测量，溅水形态的捕捉，开展了缩比模型刚性、弹性、楔形体、弧形体结构物入水的冲击响应试验，获得了结构物垂直和水平入水响应参数，为SPH算法验证提供了数据。（2）界面算法方面，推导了可获得稳定矩阵逆的FPM算法和具有高阶精度的RDSPH算法，可显著提高算法的计算效率和计算精度；在结构物入水界面问题处理时考虑界面力的DSPH算法能获得均匀稳定的弹性体应力分布。（3）工程应用方面，考察了固-液-气界面的SPH接触算法；基于缩比关系研究了楔形体入水结构物响应，并推广至飞机迫降中最优姿态的控制；在此基础上，开展了返回舱水上回收、飞机轮胎溅水和脆性材料高速破碎等问题的SPH方法分析计算，推动了该算法在复杂工程问题中的应用。（4）基于复杂工程问题计算规模的需要，增加了自主研发SPH算法并行计算程序的研究内容，注册了“基于无网格SPH方法的冲击动力学仿真软件 v1.0”，开发了基于OpenMP/MPI/GPU的并行策略，通过楔形体入水算例研究，计算规模和计算效率获得了极大提升，GPU并行后的计算效率达到国际先进水平。