高超声速圆锥边界层转捩反转数值研究

Numerical Study on Transition Reversal of Hypersonic Cone Boundary Layer

为研究高超声速边界层转捩中存在的转捩反转现象,基于雷诺平均的N-S方程,采用γ转捩模型对高超声速圆锥体绕流进行数值模拟,得到了圆锥边界层转捩位置随攻角、头部钝度的变化规律,分析了圆锥边界层转捩反转现象的流动机理.结果表明:当圆锥头部钝度增大到一定值时,圆锥边界层转捩位置随攻角增大呈现迎风面提前、背风面推迟的反转现象;圆锥边界层转捩出现攻角反转现象时,迎风面摩阻系数明显大于背风面摩阻系数且转捩前后摩阻变化更大,此时应重点关注迎风面的热防护;在零攻角条件下,随着圆锥头部钝度从很小值逐渐增大,圆锥边界层转捩位置呈现出“N”型反转现象;圆锥头部钝度增大到一定值时出现的边界层转捩反转现象的可能原因是随钝度增大头部激波后熵层高度显著增大引起的.

In order to study the transition reversal phenomenon in the transition of the hypersonic boundary layer,based on the Reynolds average N-S equation, the flow around a hypersonic cone was numerically simulated with a γ transition model, obtaining the changing law of the transition position of the cone boundary layer with the attack angle and the bluntness of the head, and analyzing the flow mechanism of the transition and reversal phenomenon of the cone boundary layer. The results show that, when the bluntness of the cone head increases to a certain value, the transition position of the cone boundary layer presents a reversal phenomenon, i.e. the windward surface advances and the leeward surface delays with the increase of the angle of attack. And when the attack angle reversal phenomenon occurs in the cone boundary layer transition, the friction coefficient on the windward surface is significantly greater than that of the leeward surface, and the friction change is greater before and after the transition, so as to pay attention on the thermal protection of the windward surface. Under the condition of zero angle of attack, the transition position of the cone boundary layer can show an "N" type reversal phenomenon with increasing the bluntness of the cone head gradually from a very small value. When the bluntness of the cone head increases to a certain value, the transition reversal phenomenon of the boundary layer occurs,may be caused by the significant increase in the height of the entropy layer after the head shock.