标题： 高阶两流体等离子体求解器用于包含完整输运现象的等离子体流动的直接数值模拟 显示英文标题

标题： High-order two-fluid plasma solver for direct numerical simulations of plasma flows with full transport phenomena

摘要： 双流体等离子体方程针对单一离子种类，包含完整的输运项，包括温度和磁场相关的离子和电子粘性应力及热通量、摩擦阻力以及欧姆加热项，已经在CFDNS代码中实现，并通过使用六阶非耗散紧致有限差分法求解不同 regimes 中的等离子体流动。 为了能够完全解析所有动态相关的时空尺度，同时保持计算可行性，做出了光速无限大和电子惯性可忽略的假设。 对双流体等离子体方程的无量纲分析表明，通过改变特征/背景数密度、长度尺度、温度和磁场强度，可以将相应的霍尔、电阻和理想磁流体动力学（MHD）方程作为极限情况恢复出来。 该双流体等离子体求解器在处理不同 regimes 中等离子体流动的准确性和鲁棒性已通过四个典型问题进行了验证： 阿尔芬波和哨声波色散关系、电磁等离子体激波和磁重联。 对于所有测试案例，通过使用物理耗散和扩散，数值耗散/扩散可忽略，当基于网格尺寸的离子雷诺数小于阈值时，可以获得完全收敛的直接数值模拟（DNS）类似解，该阈值在本研究中约为2.3。 对于磁重联问题，结果表明当离子和磁雷诺数足够大时，磁通量饱和时间和值都会收敛。 因此，DNS类似的结果变得与具有更大雷诺数的实际问题相关。 显示英文摘要

摘要： The two-fluid plasma equations for a single ion species, with full transport terms, including temperature and magnetic field dependent ion and electron viscous stresses and heat fluxes, frictional drag force, and ohmic heating term have been implemented in the CFDNS code and solved by using sixth-order non-dissipative compact finite differences for plasma flows in several different regimes. In order to be able to fully resolve all the dynamically relevant time and length scales, while maintaining computational feasibility, the assumptions of infinite speed of light and negligible electron inertia have been made. Non-dimensional analysis of the two-fluid plasma equations shows that, by varying the characteristic/background number density, length scale, temperature, and magnetic strength, the corresponding Hall, resistive, and ideal magnetohydrodynamics (MHD) equations can be recovered as limiting cases. The accuracy and robustness of this two-fluid plasma solver in handling plasma flows in different regimes have been validated against four canonical problems: Alfven and whistler dispersion relations, electromagnetic plasma shock, and magnetic reconnection. For all test cases, by using physical dissipation and diffusion, with negligible numerical dissipation/diffusion, fully converged Direct Numerical Simulations (DNS)-like solutions are obtained when the ion Reynolds number based on grid size is smaller than a threshold value which is about 2.3 in this study. For the magnetic reconnection problem, the results show that the magnetic flux saturation time and value converge when the ion and magnetic Reynolds numbers are large enough. Thus, the DNS-like results become relevant to practical problems with much larger Reynolds numbers.