标题： 低频激波振荡与抖动胞结构关系的变分模态分解分析 显示英文标题

标题： Variational mode decomposition analysis of the relationship between low-frequency shock-wave oscillations and buffet cells

摘要： 本研究探讨了NASA通用研究模型主翼上低频激波振荡与抖振胞状结构之间的关系。 流动条件设定为马赫数0.85，雷诺数2.27$\times$ 10$^6$，攻角为4.82$^{\circ}$。 抖振胞状结构具有展向周期性的细胞图案，向翼尖传播，其无量纲频率（斯特劳哈尔数）为0.2--0.6，高于与跨音速抖振相关的激波振荡频率。 然而，驱动抖振胞状结构的物理机制及其与低频激波运动的相互作用尚未完全明确。 本研究采用基于变分模态分解的非平稳相干结构（VMD-NCS）分析方法，对非定常压力敏感涂料测量数据进行分析。 结果表明，抖振胞状结构的振幅并未直接与低频激波振荡耦合，而是与边界层分离状态相关。 在持续分离区域（中段），强烈的抖振胞状结构波动持续存在，而在间歇性分离区域（外侧），其振幅随局部分离/再附着动力学变化。 这些观察结果表明，激波对于产生边界层分离所需的逆压梯度至关重要，但它们对抖振胞状结构的影响取决于 resulting 分离行为。 本研究中的实验观察所得见解与先前计算研究的结论一致，即抖振胞状结构行为依赖于边界层分离特性。 此外，本研究展示了VMD-NCS分析方法在研究具有多种空间和时间模式的非平稳流体现象方面的有效性。 显示英文摘要

摘要： This study investigates the relationship between low-frequency shock-wave oscillations and buffet cells on the main wing of the NASA common research model. The flow conditions were set at a Mach number of 0.85, Reynolds number of 2.27 $\times$ 10$^6$, and angle of attack of 4.82$^{\circ}$. Buffet cells are cellular patterns with spanwise periodicity that propagate toward the wing tip, with nondimensional frequencies (Strouhal numbers) of 0.2--0.6, higher than those of shock oscillations associated with transonic buffet. However, the physical mechanisms driving buffet cells and their interaction with low-frequency shock motion are not fully understood. This study employs variational mode decomposition-based nonstationary coherent structure (VMD-NCS) analysis applied to unsteady pressure-sensitive paint measurement data. The results reveal that the amplitude of buffet cells is not directly coupled to the low-frequency shock-wave oscillations but instead shows correlation with the boundary layer separation state. Strong buffet cell fluctuations persist in regions of sustained separation (midspan), while their amplitude varies with local separation/reattachment dynamics in regions of intermittent separation (outboard). These observations suggest that shock-waves are important to generate the adverse pressure gradient necessary for boundary layer separation, but their influence on buffet cells depends on the resulting separation behavior. This insight from experimental observations in this study is consistent with previous computational studies suggesting that buffet cell behavior depends on boundary layer separation characteristics. Moreover, this study demonstrates the effectiveness of VMD-NCS analysis for investigating nonstationary fluid phenomena with multiple spatial and temporal patterns.