Abstract A series of direct numerical simulations of turbulent porous-walled channel flows is performed to extensively investigate the influence of wall permeability on turbulence modification. The bulk mean Reynolds number is fixed at 3000, and porous media consisting of perforated plates are considered in the lower side of the channel. The mean-permeability Reynolds number is varied from 14 − 118 by varying the hole size of the perforated plates. A spectral analysis reveals the presence of two characteristic perturbation modes, namely, the streamwise perturbation mode originating from the Kelvin–Helmholtz (K–H) type of instability and the spanwise perturbation mode. When the mean permeability Reynolds number is relatively low, the streamwise perturbation model by the K–H instability is dominant, and this increases the coherence of the wall-ward turbulence motion, thus resulting in considerable turbulence enhancement. However, as the mean permeability Reynolds number increases further, the streamwise perturbations tend to decrease in strength, and the streamwise elongated high- and low-speed streaky structure, the mean spacing of which is much longer than that over a smooth wall, is developed owing to the spanwise perturbation mode. In this regime, the turbulence enhancement effect is weakened because of an increased slippage velocity at the porous interface.

中文翻译：

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壁渗透率对湍流影响的广泛研究

摘要 对湍流多孔壁通道流动进行了一系列直接数值模拟，以广泛研究壁渗透率对湍流修正的影响。体积平均雷诺数固定为 3000，通道下侧考虑多孔板组成的多孔介质。通过改变穿孔板的孔尺寸，平均渗透率雷诺数在 14 - 118 之间变化。频谱分析揭示了两种特征扰动模式的存在，即源自开尔文-亥姆霍兹 (K-H) 型不稳定性的流向扰动模式和展向扰动模式。当平均渗透率雷诺数较低时，K-H不稳定性的流向扰动模型占主导地位，这增加了壁面湍流运动的相干性，从而导致了相当大的湍流增强。但随着平均渗透率雷诺数的进一步增大，流向扰动强度趋于降低，形成流向拉长的高低速条状结构，其平均间距远大于光滑壁面上的条状结构。由于展向扰动模式。在这种情况下，由于多孔界面处的滑移速度增加，湍流增强效应减弱。由于展向扰动模式，其平均间距远大于光滑壁上的平均间距。在这种情况下，由于多孔界面处的滑移速度增加，湍流增强效应减弱。由于展向扰动模式，其平均间距远大于光滑壁上的平均间距。在这种情况下，由于多孔界面处的滑移速度增加，湍流增强效应减弱。