AI 中文总结
研究高雷诺数下零和低至中等逆压梯度湍流边界层，用两个互补数据集，证实壁面尺度涡层次结构的几何自相似性，发现多数APG诱导能量与壁面不相干，解释方差剖面偏离，还识别出能量放大结构及相关动力学特征。
AI 中文摘要
本研究比较了零和低至中等逆压梯度下的高雷诺数湍流边界层，表明两种流动中壁面尺度附着涡层次结构和上层结构具有相似的尺度和能量贡献。主要差异出现在外部/尾流区域，随着压力梯度强度增加，APG诱导的能量增强与外部尺度的嵌入式剪切层型组织相关，该组织逐渐穿透对数区域。分析使用了两个互补数据集，结果证实了壁面尺度涡层次结构的几何自相似性，且大部分额外的APG诱导能量与壁面不相干，这解释了方差剖面与经典高雷诺数边界层中逆对数定律的偏离。条件平均识别出了能量放大的结构，结果将增强的外部区域雷诺应力、平均速度剖面中的外部拐点以及雷诺剪切应力的喷射-扫掠组织联系起来，这些都是剪切层动力学的特征。
英文摘要
This study compares high-Reynolds-number turbulent boundary layers under zero and low-to-moderate adverse pressure gradients, showing similar scaling and energy contributions from the wall-scaled attached-eddy hierarchy and superstructures in both flows. The main differences occur in the outer/wake region, where APG-induced energisation is linked to an outer-scaled, embedded-shear-layer-type organisation that progressively penetrates the logarithmic region as the pressure-gradient strength increases. The analysis uses two complementary datasets for ZPG and APG boundary layers at matched friction Reynolds numbers of approximately 10,000, with minimal upstream pressure-gradient history: a new two-point hot-wire dataset and a previously published two-dimensional particle image velocimetry dataset. In the hot-wire experiment, one probe is fixed near the wall while the second traverses the full boundary layer, allowing estimation of the linear coherence spectrum. The results confirm the geometric self-similarity of the wall-scaled eddy hierarchy that remains coherent with the wall. Using the linear coherence spectrum as a spectral filter shows that most of the additional APG-induced energy is incoherent with the wall and is linearly superimposed on the wall-coherent component of the streamwise variance. This wall-incoherent contribution explains the departure of the variance profile from the inverse logarithmic law observed in canonical high-Reynolds-number boundary layers. Conditional averaging of the particle image velocimetry data identifies the structures responsible for this energy amplification. The results link enhanced outer-region Reynolds stresses, an outer inflection point in the mean velocity profile, and an ejection-sweep organisation of Reynolds shear stress, all characteristic of shear-layer dynamics.
Comments27 page, 13 figures, for the the consideration of journal of fluid mechanics
