The effects of thermal conductivity and viscosity of argon on shock waves diffracting over rigid ramps
The effects of thermal conductivity and viscosity of argon on shock waves diffracting over rigid ramps
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氩气的热导率和粘度对刚性坡道上衍射冲击波的影响
DOI：
10.1017/s0022112096003850
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发表时间：
1997
影响因子：
3.7
通讯作者：
R. J. Virgona
中科院分区：
文献类型：
--
作者：
L. F. Henderson;W. Crutchfield;R. J. Virgona
实验是用强激波在浸入氩气中的钢坡道上衍射来完成的。实验的数值模拟是通过将Navier-Stokes方程与使用等温无滑移边界条件的高阶Goddom有限差分数值格式相结合来完成的。绝热，滑移边界条件进行了研究，以模拟腔型衍射。给出了理想气体欧拉数值格式的一些结果，以供比较.当斜板角θ足够小而引起马赫反射MR时，发现真实的气体效应延迟了它的出现，并且它的激波三相点轨迹最初是弯曲的，随着MR演化成自相似系统，它最终变成直线。衍射是延迟状态下的规则反射RR，随后被超过RR的角信号扫去，并迫使马赫激波爆发。动态转变发生在或接近理想气体脱离准则θe。拐角信号的通过以粘性边界层厚度的大振荡为标志。随着θ的增加，MR的开始延迟随着动力学过程的减慢而增加。一旦建立了自相似性，则支持冯诺依曼准则。虽然冯·诺依曼准则的证据是强有力的，但由于数值上的花费，它不是决定性的。延迟过渡导致轨迹的一些实验数据受到简单视差误差的影响。当θ < θe时，自相似流的绝热滑移边界条件也支持冯·诺依曼准则，但轨迹角在θe处不连续地变为零，因此与实验相反，θe得到数值的支持。
Experiments were done with strong shocks diffracting over steel ramps immersed in argon. Numerical simulations of the experiments were done by integrating the Navier–Stokes equations with a higher-order Godunov finite difference numerical scheme using isothermal non-slip boundary conditions. Adiabatic, slip boundary conditions were also studied to simulate cavity-type diffractions. Some results from an Euler numerical scheme for an ideal gas are presented for comparison. When the ramp angle θ is small enough to cause Mach reflection MR, it is found that real gas effects delay its appearance and that the trajectory of its shock triple point is initially curved; it eventually becomes straight as the MR evolves into a self-similar system. The diffraction is a regular reflection RR in the delayed state, and this is subsequently swept away by a corner signal overtaking the RR and forcing the eruption of the Mach shock. The dynamic transition occurs at, or close to, the ideal gas detachment criterion θe. The passage of the corner signal is marked by large oscillations in the thickness of the viscous boundary layer. With increasing θ, the delay in the onset of MR is increased as the dynamic process slows. Once self-similarity is established the von Neumann criterion is supported. While the evidence for the von Neumann criterion is strong, it is not conclusive because of the numerical expense. The delayed transition causes some experimental data for the trajectory to be subject to a simple parallax error. The adiabatic, slip boundary condition for self-similar flow also supports the von Neumann criterion while θ < θe, but the trajectory angle discontinuously changes to zero at θe, so that θe is supported by the numerics, contrary to experiments.