近轴对称内收缩流场中的激波干扰

Shock interactions in near-axisymmetric internal contraction flows

针对高超声速三维内转式进气道中的复杂曲面激波干扰问题,提炼出不同来流迎角下的内收缩直锥流场,采用激波风洞实验观测结合数值模拟的方法,高效揭示小幅偏离轴对称状态时,内收缩直锥流场中的激波汇聚效应及干扰机理。结果表明:在轴对称情况下,即使内收缩直锥的前缘压缩角很小,由于汇聚效应,激波逐渐增强,在轴线上必然发生马赫反射并形成马赫盘,继而终止了激波的进一步汇聚增强;而在来流有迎角情况下,流场小幅度偏离轴对称后,表现出复杂的三维特征;沿流向迎风侧激波的汇聚增强比背风侧更快,在对称面上迎风侧和背风侧激波干扰的位置偏离轴线,并且可以发生规则反射;在对称面发生规则反射的情况下,激波反射后局部能够达到的压力比发生马赫反射的情况下马赫盘后的压力更高;随着内收缩直锥前缘压缩角的增大,对称面上发生规则反射时的临界迎角也呈现增大趋势。

The near-axisymmetric contraction flow in internal cones with different angles of attack is proposed to simplify the complicated three-dimensional shock interactions in a hypersonic inward-turning inlet.The interactions of the shock at near-axisymmetric contraction conditions are revealed efficiently using a combination of experiments in a shock tunnel and numerical simulations.The results show that the axisymmetric incident shock strengthens toward the central axis due to the convergence effect until a Mach disk is formed.It has been shown that the Mach reflection at the central axis is an inevitable phenomenon,which prevents the convergence and enhancement of the axisymmetric incident shock even for a small compression angle of the leading edge of the internal cone.However,when the incoming flow has an angle of attack,the flow field deviates slightly from the axisymmetric state and presents complex three-dimensional characteristics.The windward incident shock strengthens faster than the leeward incident shock along the flow direction.As a result,the shock interaction position on the symmetry plane deviates from the axis and the regular reflection can occur.The local pressure immediately downstream the reflection position for the regular reflection can reach a much higher level than that behind the Mach disk for the conditions where the Mach reflection occurs.Moreover,with the increase of the leading edge compression angle of the internal cone,the critical angle of attack for the appearance of the regular reflection on the symmetry plane also increases.