水中电爆炸金属丝阵形成强汇聚冲击波的研究

Converging strong shock wave generated by underwater electrical explosion of wire array has good application prospects in researches related to impact loading and inertial confinement fusion. However, it is still in a groping phase. This project intends to carry out the research on the formation of converging strong shock wave generated by underwater electrical explosion of cylindrical and spherical wire array, and the main tasks include: ① Diagnostic of density distribution of water medium behind wave front. Thermodynamic theory tells us that for thermodynamic parameters such as pressure, density, temperature, internal energy and enthalpy, we just need to get two of them and then can determine the remaining parameters according to the material equation of state (EOS). However, only the shock wave pressure can be diagnosed at present. In this project, an M-Z laser interferometer will be used to diagnose the density distribution of water medium. Based on the diagnostic results of the interferometer and a pressure probe, we can achieve a comprehensive description of the thermodynamic properties of water media behind wave front. ② Diagnostic of wave front shape of converging shock wave and study on the adjustment technique for symmetry degree of wave front shape. For cylindrical and spherical wire array, by means of laser shadowgraphy, the time and space resolved images of wave front will be obtained under different conditions, and the effects of various factors (such as wire spacing, wire array radius, wire radius, and driving current waveform) on the symmetry degree of wave front will also be studied. The results of this project would provide us a better understanding of propagation characteristics of converging shock wave and basic experimental data to develop and validate the hydrodynamic (HD) model.

水中电爆炸金属丝阵形成的强汇聚冲击波在冲击加载、惯性约束核聚变研究方面有重要应用前景，目前只处于探索研究阶段。本课题开展水中电爆炸金属丝阵（柱形、球形）形成强汇聚冲击波研究，主要研究内容为：①水中冲击波特性参数：波后水介质密度分布的诊断研究。对于压力、密度、温度、内能、焓这几个热力学参数，只需知道其中两个参数便能根据物态方程确定其余参数，但目前唯一能诊断的只有冲击波压力。本课题拟采用M-Z激光干涉法对波后介质密度分布进行诊断，以全面描述波后介质热力学性质。②汇聚冲击波波前时空演化的诊断及对称性调整技术研究。针对柱形、球形丝阵，基于激光阴影法，获取不同实验条件下汇聚.冲击波波前形态的时空演化图像，掌握各影响因素（丝间距、丝阵半径、丝半径、驱动电流波形等）对波前对称性的影响规律，实现对波前对称性的调整。项目成果有助于深入理解丝阵汇聚冲击波传输特性，还可提供建立及校验流体力学模型所需实验数据。

基于冲击加载、惯性约束核聚变研究的需要，本课题开展水中电爆炸金属丝阵形成强汇聚冲击波的研究，获取汇聚冲击波波前形态的时空演化图像，掌握各影响因素对波前对称性的影响规律，深入理解丝阵汇聚冲击波传输特性。主要研究成果如下：.（1）基于拉格朗日描述，建立了水中单丝电爆炸的单温磁流体动力学模型，并给出一种高阶混合有限元离散求解方法，该离散方法具有较好的多介质界面追踪能力和激波分辨能力。实现了水中金属丝电爆炸加热相变、放电模式转变、冲击波的产生与传播、波后区热力学参数分布变化等物理过程的自洽模拟。.（2）对水中金属丝阵电爆炸的冲击波汇聚过程进行了二维流体模拟，结果表明：冲击波汇聚过程中，自调整现象及压力的非线性叠加是因为强冲击波下进入非线性反射模式形成了马赫杆，以及马赫杆之间出现二次反射而引起。.（3）利用欠热状态下的单丝电爆炸实验，成功分离了液化冲击波和汽化冲击波，首次记录了液化冲击波的波形，并观察到了汽化冲击波追赶液化冲击波的过程。采用旁路水间隙开关，分离了汽化冲击波和电弧等离子体冲击波，发现在相同耗能的条件下，汽化冲击波的峰值压力远大于等离子体冲击波，其原因是丝爆过程的能量沉积功率远大于等离子体电弧功率。.（4）对水中金属单丝、丝阵爆炸产生冲击波及其传播过程实现了激光成像（阴影、干涉）诊断。对单丝负载，发现粗细不均匀导致的局部微爆炸现象和多个沉积功率峰导致的多层冲击波现象；对丝阵负载，获取了汇聚冲击波波前形态的时空演化过程。.（5）保持驱动源参数、负载总质量不变：提出了“分裂丝”丝阵的概念，将单丝分裂为多根并联细丝，实验表明冲击波随着“分裂丝”数量的增多而显著提高；提出了“串并联丝”丝阵的概念，将丝阵中各丝串、并联混合，实验表明，因负载动态电阻在更长时间范围内与电源内阻接近“匹配”从而获得了更强冲击波。