Conventional shock-wave–turbulent boundary-layer interactions are often treated as quasi-two dimensional for a tractable analysis. In practical applications such as high-speed engine inlets and combustors, the additional presence of sidewalls leads to dramatic changes in the baseline flow structure by enhancing the inherent three dimensionality of the interaction, in addition to modifying its unsteadiness. This study investigates the flow field generated by a ${24}^{\circ }$ compression ramp in presence of sidewalls, with a confinement ratio $\delta /w=0.12$. The free-stream unit Reynolds number and Mach number are $2.5\times {10}^7{\mathrm{m}}^{-1}$ and 2.25, respectively. Statistical analysis of results obtained from high-fidelity simulations carried out by Poggie and Porter [Phys. Rev. Fluids 4, 024602 (2019)] is performed to explore the large-scale unsteadiness of this flow field. The mean and instantaneous flow fields displayed strong three dimensionality due to influence of sidewalls. Fourier analysis of wall-pressure data revealed frequency bands typically associated with low-frequency shock oscillations, $\text{St}\approx O\left(0.01\right)$, as well as vortex shedding occurring at mid frequencies, $\text{St}\approx O\left(0.1\right)$. The spectra of shock oscillations and separation bubble breathing indicated a dominant low- and mid-frequency component, respectively, akin to a quasi-two-dimensional shock-induced separation. The centerline shock oscillations were well correlated with the breathing motion of the centerline separation bubble, as well as turbulence in the upstream boundary layer. Effects of sidewalls on the overall unsteadiness were investigated by estimating coherence and correlations between various quantities. Plots of coherence between shock motion and pressure fluctuations in the domain indicated asymmetric motion of the interaction, possibly caused by alternating breathing motion of the separated zones on the sidewalls. Space-time correlations on the floor suggested a strong influence of centerline separation on the corner separations and vice versa. Similar correlations with left and right sidewalls confirmed the asymmetric motion of the interaction with a frequency of $\text{St}\approx 0.026$.

中文翻译：

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侧壁限制的压缩坡道流动中的大规模不稳定

常规的冲击波-湍流边界层相互作用通常被视为准二维，以便进行易处理的分析。在诸如高速发动机进气口和燃烧器的实际应用中，除了改变其不稳定性之外，侧壁的额外存在还通过增强了相互作用的固有三维性，导致基线流动结构发生了戏剧性的变化。这项研究调查了由${24}^{\circ }$ 有侧壁的压缩坡道，具有约束比 $\delta /w=0.12$。自由流单位雷诺数和马赫数为$2.5\times {10}^7{\mathrm{米}}^{-\mathrm{1个}}$和2.25。对Poggie和Porter进行的高保真模拟所获得的结果进行统计分析[ Phys。修订版液 4，024602（2019）]进行探索这个流场的大型晃动。由于侧壁的影响，平均和瞬时流场显示出很强的三维性。壁压数据的傅立叶分析揭示了通常与低频冲击振荡相关的频带，$\text{英石}\approx Ø（0.01）$以及中频发生的涡旋脱落 $\text{英石}\approx Ø（0.1）$。冲击振荡和分离气泡呼吸的光谱分别表明了主要的低频分量和中频分量，类似于准二维冲击诱导的分离。中心线震荡振荡与中心线分离气泡的呼吸运动以及上游边界层的湍流密切相关。通过估计各种量之间的连贯性和相关性，研究了侧壁对整体不稳定的影响。区域中的冲击运动和压力波动之间的相干图表示相互作用的不对称运动，这可能是由于侧壁上各个分离区域的交替呼吸运动引起的。地板上的时空相关性表明，中心线间距对拐角间距有很大的影响，反之亦然。$\text{英石}\approx 0.026$。