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首页> 外文会议>AIAA aviation forum;AIAA fluid dynamics conference >Investigation of Unsteadiness in a Mach 2 Swept-Ramp Shock/Boundary-Layer Interaction Using 50 kHz PIV
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Investigation of Unsteadiness in a Mach 2 Swept-Ramp Shock/Boundary-Layer Interaction Using 50 kHz PIV

机译：使用50 kHz PIV对2马赫扫掠激波/边界层相互作用中的不稳定性进行研究

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This experimental study aims to examine the flow structure and unsteadiness of 3D shock-wave/boundary-layer interactions. The interaction examined here is generated by a swept compression ramp in a Mach 2 flow. The ramp has a streamwise angle of 22.5° with a sweep angle of 30°. The primary diagnostics used here are wide-field 5 Hz PIV and 50 kHz PIV using a pulse-burst laser. The 50 kHz PIV in streamwise-transverse planes is used to analyse the large-scale fluctuations in the separation bubble size. Since the 50 kHz sampling rate is significantly higher than the frequencies that characterizes the large-scale separated flow dynamics, the data can be bandpass-filtered to investigate potential mechanisms that drive the unsteadiness. Three distinct frequency bands are investigated: 10kHz to 50kHz (0.25 to 1.25U_∞/δ_(99)), 1kHz to 10kHz (0.025 to 0.25 U_∞/δ_(99)), and 0kHz to 1khz (0 to 0.025U_∞/δ_(99)). The majority of the literature in 2D interactions reports that the large-scale unsteadiness of the separated flow occurs in the 0.01-0.1U_∞/δ_(99) frequency band; however this study finds that significant large-scale unsteadiness occurs with frequency content above this range. For separated flow motions above 0.25U_∞/δ_(99) there is little correlation with upstream boundary-layer fluctuations. It is yet unknown if the observed high frequency motions of the separated flow (＞10kHz) are unique to 3D interactions. In contrast, the large-scale unsteadiness associated with the frequency range 0.025-0.25U_∞/δ_(99) shows a strong correlation with the upstream boundary-layer velocity fluctuations, and this frequency band is similar to the frequencies that characterize undisturbed boundary-layer superstructures. Finally, separation bubble motions with frequencies below 0.025U_∞/δ_(99) showed the strongest correlation with upstream boundary-layer velocity fluctuations. It is also of note that the amplitude of the large-scale separated flow motions depend on the frequency band. For example, the large-scale motions most correlated with the upstream boundary layer (＜ 1kHz) exhibit variations in the scale of separation that are only about 30% of the amplitudes exhibited at higher frequencies. This single result may explain why different studies have reported apparently contradictory results regarding the influence of upstream velocity fluctuations.
机译：这项实验研究旨在检查3D冲击波/边界层相互作用的流动结构和不稳定性。此处检查的相互作用是由Mach 2流中的扫掠压缩斜坡产生的。坡道的流向角为22.5°，后掠角为30°。此处使用的主要诊断方法是使用脉冲猝发激光器的宽视场5 Hz PIV和50 kHz PIV。流横向平面中的50 kHz PIV用于分析分离气泡尺寸的大规模波动。由于50 kHz的采样率显着高于表征大规模分离流动动力学的频率，因此可以对数据进行带通滤波以研究驱动不稳定的潜在机制。研究了三个不同的频段：10kHz至50kHz（0.25至1.25U_∞/δ_（99）），1kHz至10kHz（0.025至0.25U_∞/δ_（99））和0kHz至1khz（0至0.025U_∞/ δ_（99））。二维相互作用中的大多数文献报道，分离流的大规模不稳定性发生在0.01-0.1U_∞/δ_（99）频带中。然而，这项研究发现，频率含量超过此范围会发生大规模的不稳定现象。对于高于0.25U_∞/δ_（99）的分离流动运动，与上游边界层波动几乎没有相关性。尚不清楚观察到的分离流的高频运动（> 10kHz）是否是3D交互所特有的。相反，与频率范围0.025-0.25U_∞/δ_（99）相关的大规模不稳定性显示出与上游边界层速度波动的强相关性，并且该频带类似于表征不受干扰边界的频率。层上层建筑。最后，频率低于0.025U_∞/δ_（99）的分离气泡运动显示出与上游边界层速度波动的最强相关性。还要注意的是，大规模分离流动运动的幅度取决于频带。例如，与上游边界层（＜1kHz）最相关的大规模运动表现出分离尺度的变化，其仅占较高频率下振幅的30％左右。这个单一的结果可以解释为什么不同的研究报告了关于上游速度波动影响的明显矛盾的结果。

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