转捩对压缩拐角激波/边界层干扰分离泡的影响

为了研究转捩对压缩拐角内分离泡结构的影响，进行了来流马赫数2.9，24°压缩拐角激波/转捩边界层干扰的直接数值模拟（DNS）。通过在拐角上游平板的不同流向位置处添加周期性吹吸扰动激发流动转捩，使得转捩不同阶段进入拐角入口，从而在拐角内产生激波/转捩边界层的相互干扰。计算得到的平均速度剖面、壁面压力分布以及分离泡大小与风洞试验及以往直接数值模拟结果吻合较好，验证了计算结果的可靠性。研究了转捩过程对角部干扰区内分离泡结构的影响规律，分析比较了不同转捩阶段下角部分离区内湍动能的生成、耗散和分配机制。研究结果表明：转捩初期的拟序涡结构对分离泡尺度及形状影响最大，发卡涡包在角部拐点附近发生展向融合，并在角部区域形成湍流斑，此时分离泡尺度最小，形状呈现中间高两边低的山峰型。随着转捩的发展，分离区内湍动能生成和近壁区的耗散逐步降低，此时输运项起到了主要的平衡作用。

Transition effect on separation bubble of shock wave/boundary layer interaction in a compression ramp

Direct numerical simulations (DNS) of shock wave and transitional boundary layer interaction for a 24°compression corner at Mach number 2.9 are performed to study the effect of transition on the separation bubble at the ramp corner. At upstream, the flat-plate transition is triggered by the periodic blow and suction disturbance. The interaction of shock wave and transitional boundary layer is then simulated by setting the length of upstream flat-plate. The extent of separation agrees well with those of the experimental and direct numerical simulation data, which validate the results. Transition effect on the separation bubble in the interaction region is researched and the turbulent kinetic energy budget in the bubble is analyzed. Results indicate that the coherent structures at the early stage of transition have a serious influence on the separation bubble, in which the turbulent spots are formed by the hairpin vortices. Then the scale of separation bubble is the smallest and the shape is spike-type in the spanwise direction. With the evolution of transition, the turbulent production and dissipation term in the separation bubble gradually reduce by four times, while the turbulent transport term contributes to the balance of the turbulent production and dissipation.