Large eddy simulations (LES) were carried out to investigate the influence of surface roughness, which was applied to the inner walls of a cooling hole, on cooling performance and flow structures. The cooling hole was a 30-degree inclined, baseline 7-7-7 fan-shaped hole relative to a turbulent flat plate boundary layer of the mainstream. Numerical simulations were performed at two different blowing ratios ($M=1.5$ and 3.0) and at a constant density ratio ($\mathit{DR}=1.5$) for various configurations of surface roughness. In order to numerically consider the effects of surface roughness, the equivalent sand-grain roughness model was utilized. Different correlations between the equivalent sand-grain roughness height and arithmetic average roughness height were numerically tested to find an accurate correlation compared to the measurements. The time-averaged numerical results were validated by experiments looking at the velocity and thermal fields for the smooth and rough cooling holes. Results revealed that increasing the surface roughness applied to the cooling hole, increases the thickness of the boundary layers within the hole, especially at the higher blowing ratio. This leads to a higher jet core flow at the cooling hole exit and lower cooling effectiveness at the flat plate surface compared with a smooth cooling hole. The minimum area-averaged film-cooling performance showed a 58% reduction compared to a smooth hole in the case of the highest blowing ratio ($M=3.0$) and the largest surface roughness height. In addition, the time-space evaluation of the velocity fluctuations showed greater flow unsteadiness and increased wavy patterns within the cooling hole in the case of rough holes.

进行大涡模拟 (LES) 以研究应用于冷却孔内壁的表面粗糙度对冷却性能和流动结构的影响。冷却孔是一个相对于主流湍流平板边界层倾斜 30 度、基线为 7-7-7 的扇形孔。在两种不同的吹塑比下进行数值模拟（$米=1.5$ 和 3.0) 并以恒定的密度比 ($\mathit{DR}=1.5$) 用于表面粗糙度的各种配置。为了在数值上考虑表面粗糙度的影响，采用等效砂粒粗糙度模型。对等效砂粒粗糙度高度和算术平均粗糙度高度之间的不同相关性进行了数值测试，以找到与测量值相比的准确相关性。通过观察光滑和粗糙冷却孔的速度和热场的实验验证了时间平均数值结果。结果表明，增加应用于冷却孔的表面粗糙度，会增加孔内边界层的厚度，尤其是在较高的吹气比下。与光滑的冷却孔相比，这会导致冷却孔出口处的喷射核心流量更高，而平板表面的冷却效率更低。在最高吹气比的情况下，最小面积平均薄膜冷却性能与光滑孔相比降低了58％（$米=3.0$) 和最大表面粗糙度高度。此外，速度波动的时空评估表明，在粗糙孔的情况下，冷却孔内的流动不稳定性更大，波浪模式增加。