This paper reports an investigation of the effects of rough forward facing steps on turbulent flows. The surfaces of the rough steps were covered with sandpapers. A particle image velocimetry technique was used to conduct measurements at the mid-plane of the test section and at several locations downstream to 68 step heights. A Reynolds number of Re_h = 4800 and δ/h = 4.7 were employed, where h is the mean step height and δ is the incoming boundary layer thickness. The results indicate that mean reattachment length decreases with increasing roughness. In addition, the effect of the step roughness decreases with downstream distance. The proper orthogonal decomposition results showed that the step roughness affects even the large scale structures. Furthermore, the reconstructed turbulence quantities suggest that the step roughness suppresses the large scale turbulence.
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机译：本文报告了粗糙的前向台阶对湍流的影响的研究。粗糙台阶的表面覆盖有砂纸。粒子图像测速技术用于在测试部分的中平面和68个台阶高度下游的几个位置进行测量。使用雷诺数Re_h = 4800和δ/ h = 4.7，其中h是平均台阶高度，δ是进入的边界层厚度。结果表明，平均重新连接长度随着粗糙度的增加而减小。另外，台阶粗糙度的影响随着下游距离而减小。正确的正交分解结果表明，台阶粗糙度甚至会影响大型结构。此外，重构的湍流量表明，台阶粗糙度抑制了大规模的湍流。
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