冲击波对多孔材料作用的模拟研究
Simulation study of shock reaction on porous material
摘要：
冲击作用下多孔材料的直接建模是一个复杂的问题。我们通过新开发的物质点方法研究这样的系统。冲击强度和孔隙尺寸的影响是主要关注的问题。对于相同的孔隙率，平均孔隙尺寸的影响进行了检查。研究发现，局部湍流混合和体积耗散是动能向热量转化的两个重要机制。当孔隙率很小时，冲击段可能达到动力学稳定状态;下游段的空隙反射稀疏波，导致平均密度和压力的轻微振荡;对于相同的孔隙率值，较大的平均空隙尺寸使得较高的平均温度。当孔隙率变大时，在整个冲击加载过程中，流体力学量随时间变化：初始阶段后，平均密度和压力下降，但温度以较高的速率上升。局部密度、压力、温度和颗粒速度的分布一般是非高斯的，并随时间变化。其变化率与孔隙度、平均孔隙尺寸和冲击强度有关。加载冲击波越强，孔隙度效应越强。这一工作是对快速程序实验的补充，揭示了能量和动量输运的更基本的机理。
英文摘要：
Direct modeling of porous materials under shock is a complex issue. We investigate such a system via the newly developed material-point method. The effects of shock strength and porosity size are the main concerns. For the same porosity, the effects of mean-void-size are checked. It is found that, local turbulence mixing and volume dissipation are two important mechanisms for transformation of kinetic energy to heat. When the porosity is very small, the shocked portion may arrive at a dynamical steady state; the voids in the downstream portion reflect back rarefactive waves and result in slight oscillations of mean density and pressure; for the same value of porosity, a larger mean-void-size makes a higher mean temperature. When the porosity becomes large, hydrodynamic quantities vary with time during the whole shock-loading procedure: after the initial stage, the mean density and pressure decrease, but the temperature increases with a higher rate. The distributions of local density, pressure, temperature and particle-velocity are generally non-Gaussian and vary with time. The changing rates depend on the porosity value, mean-void-size and shock strength. The stronger the loaded shock, the stronger the porosity effects. This work provides a supplement to experiments for the very quick procedures and reveals more fundamental mechanisms in energy and momentum transportation.
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