The effect of a turbulent boundary layer subjected to a series of rounded edged shallow dimple arrays with dimple depth ratios, d/D of 4%, 8% and 12% were experimentally studied. Measurements show the existence of a higher flow speed region at the center of each dimple. The spanwise distribution of the mean wall shear stress immediately downstream of the centers of the last row of dimples does not vary with dimple depth, and is about 45% over that without the dimple array. Turbulence measurements and surface flow visualization shows that the flow over the shallowest dimple differs from the deeper dimples. Flow separation observed with the deeper rounded edged dimples produce similar flow structures as those from sharp edged dimples reported in the literature. However flow separation is not observed when d/D=4% but instead two other higher speed regions either side accompany the central flow. The effects of the dimples are rapidly suppressed by the flat surfaces between of the dimples, and the flow rapidly reverts back to an unmanipulated flat boundary layer flow in these areas.

中文翻译：

---

圆边凹坑阵列对边界层发展的影响

实验研究了湍流边界层受到一系列具有凹坑深度比、d/D 为 4%、8% 和 12% 的圆形边缘浅凹坑阵列的影响。测量显示在每个凹坑的中心存在更高的流速区域。紧邻最后一排凹坑中心下游的平均壁面剪应力的展向分布不随凹坑深度而变化，比没有凹坑阵列的情况高出约 45%。湍流测量和表面流动可视化表明，最浅凹坑上的流动与较深凹坑不同。用更深的圆形边缘凹坑观察到的流动分离产生与文献中报道的尖锐边缘凹坑相似的流动结构。然而，当 d/D=4% 时没有观察到流动分离，而是在中央流动两侧伴随着另外两个高速区域。凹坑之间的平坦表面迅速抑制了凹坑的影响，并且在这些区域中流动迅速恢复为未受操纵的平坦边界层流。