高超声速圆柱绕流中驻点热流的稀薄效应

采用Fay-Riddell关系式、直接模拟Monte Carlo方法和基于直接模拟Monte Carlo流场温度的Fourier传热三种热流表达方式,分别对比研究了不同来流克努森数(Kn)和不同来流马赫数(Ma)的结果,以期从微观视角给出经典连续方法在稀薄流区高估驻点热流的新理解。结果表明,驻点热流的稀薄效应体现在三个方面:一是温度跳跃,削弱温度梯度导致驻点热流降低；二是壁面附近平动非平衡,导致Fourier热传导定律失效且高估热流；三是壁面约束,致使Fourier热传导定律在距壁面3倍分子平均自由程内高估热流。

Rarefaction effect on the stagnation point heat flux in hypersonic cylinder flows

The Fay-Riddell correlation, direct simulation Monte Carlo method, and the Fourier heat transfer expression based on direct simulation Monte Carlo flow field temperature were considered. Cases with different freestream Knudsen numbers (Kn) and Mach numbers (Ma) were studied to provide a new understanding of the classical continuum method to overestimate the stagnation point heat flux in the rarefied region from the microscopic perspective. The related results show that the rarefied effect on the stagnation point heat flux includes three aspects. The temperature jump upon the wall decreases the temperature gradient, reducing the stagnation point heat flux. The translational nonequilibrium was found near the wall, which leads to the failure of the Fourier heat conduction law and overestimates the heat flux. The wall-bound effect makes the Fourier heat conduction law overestimates the heat flux located three times the mean free path away from the wall.