Highly resolved two- and three-dimensional computational fluid dynamics (CFD) simulations are presented for shock-tube experiments containing hydrogen/oxygen (H2/O2) mixtures, to investigate mechanisms leading to remote ignition. The results of the reactive cases are compared against experimental results from Meyer and Oppenheim (Proc Combust Inst 13(1): 1153–1164, 1971. https://doi.org/10.1016/s0082-0784(71)80112-1 ) and Hanson et al. (Combust Flame 160(9): 1550–1558, 2013. https://doi.org/10.1016/j.combustflame.2013.03.026 ). The results of the non-reactive case are compared against shock tube experiments, recently carried out in Duisburg and Texas. The computational domain covers the end-wall region of the shock tube and applies high order numerics featuring an all-speed approximate Riemann scheme, combined with a 5th order interpolation scheme. Direct chemistry is employed using detailed reaction mechanisms with 11 species and up to 40 reactions, on a grid with up to 2.2 billion cells. Additional two-dimensional simulations are performed for non-reactive conditions to validate the treatment of boundary-layer effects at the inlet of the computational domain. The computational domain covers a region at the end part of the shock tube. The ignition process is analyzed by fields of localized, expected ignition times. Instantaneous fields of temperature, pressure, entropy, and dissipation rate are presented to explain the flow dynamics, specifically in the case of a bifurcated reflected shock. In all cases regions with locally increased temperatures were observed, reducing the local ignition-delay time in areas away from the end wall significantly, thus compensating for the late compression by the reflected shock and therefore leading for first ignition at a remote location, i.e., away from the end wall where the ignition would occur under ideal conditions. In cases without a bifurcated reflected shock, the temperature increase results from shock attenuation. In cases with a bifurcated reflected shock, the formation of a second normal shock and shear near the slip line is found to be crucial for the remote ignition to take place. Overall, the two- and three-dimensional simulations were found to qualitatively explain the occurrence of remote ignition and to be quantitatively correct, implying that they include the correct physics.

中文翻译：

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冲击管远程点火的数值研究

为包含氢/氧 (H2/O2) 混合物的激波管实验提供了高分辨率的二维和三维计算流体动力学 (CFD) 模拟，以研究导致远程点火的机制。将反应案例的结果与 Meyer 和 Oppenheim 的实验结果进行比较（Proc Combust Inst 13(1): 1153–1164, 1971. https://doi.org/10.1016/s0082-0784(71)80112-1）和汉森等人。（燃烧火焰 160(9)：1550-1558，2013 年。https://doi.org/10.1016/j.combustflame.2013.03.026）。将无反应案例的结果与最近在杜伊斯堡和德克萨斯州进行的激波管实验进行了比较。计算域覆盖了激波管的端壁区域，并应用了具有全速近似黎曼方案的高阶数值，并结合了 5 阶插值方案。在具有多达 22 亿个细胞的网格上，使用具有 11 个物种和多达 40 个反应的详细反应机制采用直接化学。对非反应条件执行额外的二维模拟，以验证计算域入口处边界层效应的处理。计算域覆盖了激波管末端的区域。点火过程通过局部的预期点火时间场进行分析。提供了温度、压力、熵和耗散率的瞬时场来解释流动动力学，特别是在分叉反射激波的情况下。在所有情况下都观察到局部温度升高的区域，显着减少了远离端壁区域的局部点火延迟时间，从而补偿由反射冲击引起的后期压缩，并因此导致在远程位置进行第一次点火，即远离在理想条件下会发生点火的端壁。在没有分叉反射冲击的情况下，温度升高是由冲击衰减引起的。在分叉反射激波的情况下，发现在滑移线附近形成第二次法向激波和剪切对于远程点火的发生至关重要。总体而言，发现二维和三维模拟可以定性地解释远程点火的发生，并且在定量上是正确的，这意味着它们包括正确的物理学。远离在理想条件下会发生点火的端壁。在没有分叉反射冲击的情况下，温度升高是由冲击衰减引起的。在分叉反射激波的情况下，发现在滑移线附近形成第二次法向激波和剪切对于远程点火的发生至关重要。总体而言，发现二维和三维模拟可以定性地解释远程点火的发生，并且在定量上是正确的，这意味着它们包括正确的物理。远离在理想条件下会发生点火的端壁。在没有分叉反射冲击的情况下，温度升高是由冲击衰减引起的。在分叉反射激波的情况下，发现在滑移线附近形成第二次法向激波和剪切对于远程点火的发生至关重要。总体而言，发现二维和三维模拟可以定性地解释远程点火的发生，并且在定量上是正确的，这意味着它们包括正确的物理。