Unsteady effects of strong shock-wave/boundary-layer interaction at high Reynolds number
Unsteady effects of strong shock-wave/boundary-layer interaction at high Reynolds number
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DOI：
10.1017/jfm.2017.308
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发表时间：
2017-06
影响因子：
3.7
通讯作者：
V. Pasquariello;S. Hickel;N. Adams
中科院分区：
文献类型：
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作者：
V. Pasquariello;S. Hickel;N. Adams
我们分析了具有强平均流分离的高雷诺数撞击冲击波/湍流边界层相互作用 (SWBLI) 的低频动力学。我们的网格融合大涡流模拟 (LES) 的流动配置再现了最近的马赫 3 湍流边界层与冲击激波相互作用的实验，该冲击波名义上使传入流偏转 $19.6^{\circ }$ 。基于 $Re_{\unicode[STIX]{x1D6FF}_{0}}\approx 203\times 10^{3}$ 的传入边界层厚度的雷诺数比之前的 LES 研究要高得多。 $3805\unicode[STIX]{x1D6FF}_{0}/U_{0}$ 的超长积分时间可以准确分析低频不稳定效应。实验壁压测量结果与 LES 数据非常吻合。两个数据集都在强 SWBLI 的分离流区域内表现出明显的平台。过滤后的三维流场显示出源自气泡顶点附近的反向旋转流向涡流的清晰证据。与之前压缩斜坡配置的数值结果相反，这些类似戈特勒的涡流并不固定在特定的展向位置，而是经历与分离气泡动力学耦合的慢速运动。与实验数据一致，壁压探头的功率谱密度（PSD）表现出与分离激波不稳定性相关的宽带和高能低频分量。对展向平均数据和壁平面快照进行稀疏促进动态模式分解（SPDMD）会产生分离气泡的经典且众所周知的低频呼吸模式，以及负责反射和重新附着激波波纹的中频脱落模式。二维皮肤摩擦系数的 SPDMD 进一步识别了低频下的流向条纹，这些条纹导致重新附着线的大规模扑动。我们的撞击 SWBLI 的 PSD 和 SDMD 结果支持了这样的理论，即相互作用区的内在机制是导致低频不稳定的原因，其中 Görtler 状涡旋可能被视为强 SWBLI 的连续（相干）强迫。
We analyse the low-frequency dynamics of a high Reynolds number impinging shock-wave/turbulent boundary-layer interaction (SWBLI) with strong mean-flow separation. The flow configuration for our grid-converged large-eddy simulations (LES) reproduces recent experiments for the interaction of a Mach 3 turbulent boundary layer with an impinging shock that nominally deflects the incoming flow by $19.6^{\circ }$ . The Reynolds number based on the incoming boundary-layer thickness of $Re_{\unicode[STIX]{x1D6FF}_{0}}\approx 203\times 10^{3}$ is considerably higher than in previous LES studies. The very long integration time of $3805\unicode[STIX]{x1D6FF}_{0}/U_{0}$ allows for an accurate analysis of low-frequency unsteady effects. Experimental wall-pressure measurements are in good agreement with the LES data. Both datasets exhibit the distinct plateau within the separated-flow region of a strong SWBLI. The filtered three-dimensional flow field shows clear evidence of counter-rotating streamwise vortices originating in the proximity of the bubble apex. Contrary to previous numerical results on compression ramp configurations, these Görtler-like vortices are not fixed at a specific spanwise position, but rather undergo a slow motion coupled to the separation-bubble dynamics. Consistent with experimental data, power spectral densities (PSD) of wall-pressure probes exhibit a broadband and very energetic low-frequency component associated with the separation-shock unsteadiness. Sparsity-promoting dynamic mode decompositions (SPDMD) for both spanwise-averaged data and wall-plane snapshots yield a classical and well-known low-frequency breathing mode of the separation bubble, as well as a medium-frequency shedding mode responsible for reflected and reattachment shock corrugation. SPDMD of the two-dimensional skin-friction coefficient further identifies streamwise streaks at low frequencies that cause large-scale flapping of the reattachment line. The PSD and SPDMD results of our impinging SWBLI support the theory that an intrinsic mechanism of the interaction zone is responsible for the low-frequency unsteadiness, in which Görtler-like vortices might be seen as a continuous (coherent) forcing for strong SWBLI.