Abstract To understand the permeability effects on turbulent rib-roughened porous channel flows, particle image velocimetry measurements are performed at the bulk Reynolds number of 5000–20000. Solid impermeable and porous ribs are considered for the rib-roughness whose geometry is categorised in the k-type roughness whose pitch/rib-height is 10. Three isotropic porous media with nearly the same porosity: 0.8, and different permeabilities (0.004, 0.020, 0.033 mm2) are applied. It is observed that the recirculation between the ribs becomes weak and the recirculation vortex submerges into the porous wall as the wall permeability and Reynolds number increase for both solid and porous rib cases while the recirculation vanishes in high permeable cases. These phenomena result in characteristic difference in turbulence quantities. By fitting the mean velocity profiles to the log-law form, the permeability effects of both rib and bottom wall on the log-law parameters and the equivalent sand-grain roughness are discussed. It is concluded that the zero-plane displacement increases while the von Karman constant and the equivalent sand-grain roughness decrease as the wall and rib permeability increases.

中文翻译：

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k型肋粗糙多孔壁上的湍流特性

摘要 为了了解渗透性对湍流肋粗糙多孔通道流动的影响，粒子图像测速测量在 5000-20000 的体积雷诺数下进行。考虑固体不渗透和多孔肋条用于其几何形状归类为节距/肋高为 10 的 k 型粗糙度。 具有几乎相同孔隙率：0.8 和不同渗透率（0.004、0.020）的三种各向同性多孔介质, 0.033 mm2) 被应用。观察到，随着壁渗透率和雷诺数的增加，肋之间的再循环变弱，再循环涡沉入多孔壁，实心和多孔肋情况下，再循环在高渗透情况下消失。这些现象导致湍流量的特征差异。通过将平均速度剖面拟合为对数定律形式，讨论了肋和底壁对对数定律参数和等效砂粒粗糙度的渗透率影响。得出的结论是，随着壁和肋渗透率的增加，零平面位移增加而冯卡门常数和等效砂粒粗糙度减小。