标题： 激波在辐射等离子体中的形成 显示英文标题

标题： Shock Wave Formation in Radiative Plasmas

摘要： 弱冲击波在辐射介质中的时间演化在此工作中被理论研究。 辐射冲击波的结构传统上是在稳态框架下研究的。 它们的系统分类是复杂的，因为光学薄层和厚层交替形成一个辐射驱动的前导区和温度弛豫层，而流体动力学冲击波嵌入在这两者之间。 在本工作中，我们分析了当两个压力不同的辐射等离子体接触时弱冲击波的形成。 应用约化摄动方法得到一个Burgers型方程，该方程描述了包括辐射场在内的扰动变量的时间演化。 已经推导出并表达出光学薄和厚解存在的条件，作为冲击波强度和玻尔兹曼数的函数。 在某个玻尔兹曼数阈值以下，弱冲击波随时间逐渐变为光学厚，而薄解则作为瞬态结构出现。 光学薄区的存在与压缩物质中过密层的存在有关。 为每种情况提供了特征形成时间和冲击波宽度的标度定律。 理论分析得到了FLASH模拟的支持，并设计了一个全面的测试案例来基准化辐射流体动力学代码。 显示英文摘要

摘要： The temporal evolution of weak shocks in radiative media is theoretically investigated in this work. The structure of radiative shocks has traditionally been studied in a stationary framework. Their systematic classification is complex because layers of optically thin and thick regions alternate to form a radiatively-driven precursor and a temperature-relaxation layer, between which the hydrodynamic shock is embedded. In this work, we analyze the formation of weak shocks when two radiative plasmas with different pressures are put in contact. Applying a reductive perturbative method yields a Burgers-type equation that governs the temporal evolution of the perturbed variables including the radiation field. The conditions upon which optically thin and thick solutions exist have been derived and expressed as a function of the shock strength and Boltzmann number. Below a certain Boltzmann number threshold, weak shocks always become optically thick asymptotically in time, while thin solutions appear as transitory structures. The existence of an optically thin regime is related to the presence of an overdense layer in the compressed material. Scaling laws for the characteristic formation time and shock width are provided for each regime. The theoretical analysis is supported by FLASH simulations, and a comprehensive test-case has been designed to benchmark radiative hydrodynamic codes.