高超声速有攻角锥裙直接数值模拟

Direct numerical simulation of hypersonic cone-flare model at angle of attack

采用直接数值模拟方法对有攻角的高超声速7°~34°锥裙开展了数值研究,通过对比0°、90°、180°周向子午面,评估了三维横流效应对激波/边界层干扰的影响规律和作用机制,包括壁面压力、摩阻、热流分布,分离泡非定常运动,再附边界层演化等。研究发现,不同周向站位均出现流动分离,横流区、迎风区内复杂激波结构与边界层相互作用导致壁面压力、摩阻、热流显著升高。热流与压力的比值在干扰区上升后由于再附降低,而热流与摩阻的雷诺比拟关系在分离区则完全失效。分离泡面积脉动的功率谱结果表明,分离泡非定常膨胀/收缩运动呈低频特征,且分离泡呼吸与激波低频振荡在横流区密切相关,在迎风区存在迟滞,而在背风区不相关。速度脉动场的本征正交分解结果表明,分离区的低频特征与低阶模态相应的剪切层附近大尺度结构相关。对下游再附边界层演化分析指出,攻角的存在导致雷诺应力在再附点附近大幅增强,其流向分量的恢复最为迅速,雷诺应力分量的峰值位置在背风区沿流向持续外移,而在迎风区、横流区已迅速向内层恢复。此外,雷诺应力各向异性不变量分布进一步表明干扰下游的近壁区湍流各向异性峰值在背风区弱于迎风区。

A direct numerical simulation of a hypersonic 7°-34°cone-flare model at an angle of attack is carried out.By comparing the flow characteristics on 0°,90°and 180°sections,we evaluate the effect of crossflow on shock wave and boundary layer interaction in terms of the distribution of wall pressure,skin friction and heat transfer,the unsteady motion of the separation bubble,and the evolution of the reattached boundary layer.It is found that the flow separation occurs near the corner,and the interaction of the shock wave and boundary layer in the crossflow and windward re⁃gion leads to a significant increase in wall pressure,skin friction,and heat transfer.The ratio of heat transfer to pres⁃sure exhibits a rise in the interaction region,followed by a drop caused by the reattachment,while the Reynolds anal⁃ogy is completely invalid in the separation zone.Low-frequent unsteady expansion/contraction motion of the separation bubble is revealed through spectral analysis of the bubble area fluctuation.It is closely related to the low frequency shock wave oscillation in the crossflow region;however,hysteresis occurs in the windward region while is irrelevant in the leeward region.Based on the proper orthogonal decomposition results of the velocity fluctuation field,the separa⁃tion region is related to large-scale structures near the shear layer in the low-order modes.The evolution of the reat⁃tached boundary layer shows the drastic Reynolds stress increase in vicinity of the reattachment point caused by the angle of attack,with the streamwise component recovering rapidly.Meanwhile,the peak location of Reynolds stress components continues to move outward in the leeward region,and has rapidly recovered to the inner layer in the wind⁃ward region and the crossflow region.In addition,the distribution of Reynolds stress anisotropy invariants further indi⁃cates that the peak value of the turbulence anisotropy in the near-wall region downstream of the interaction is weaker in the leeward region than in the windward region.