Abstract

Present study aims to illustrate the role of form-induced shear stress on turbulent kinetic energy (TKE) budget distributions in permeable gravel bed streams. In order to achieve the objective of this study, some significant experimental works on turbulent flow characteristics over rough beds are reviewed first and compared with the results of present studies. Uniform gravels (d₅₀ = 4 cm) are arranged randomly in five layers on a 15 cm long open channel. The bed topography and porosity induces spatially heterogeneous flow fields in the near-bed region and to resolve the spatial heterogeneity of flows above and within the flow-gravel-bed interface the traditional time-averaging approach is supplemented by the double-averaging (DA) concept. The form induced shear stress (FISS) depicts significant role in order to obtain total turbulent stress and found to be 40% of the DA Reynolds shear stress (RSS) occurring at the virtual bed level. Also, TKE budget distributions reveal that the TKE production, dissipation and pressure energy diffusion attains maximum values above the virtual bed level and decreases sharply below it. Importantly, the pressure energy diffusion shows a negative magnitude below the gravel crest. Moreover, the TKE dissipation rate is considerably smaller than its production rate above and within the flow-gravel-bed interface.

中文翻译：

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形式诱导剪应力对可渗透砾石床流中流动-砾石-床界面上方和内部湍动动能收支分布的影响——比较研究

摘要

本研究旨在说明形状诱导剪切应力对可渗透砾石床流中湍动能 (TKE) 收支分布的作用。为了实现本研究的目标，首先回顾了一些关于粗糙床湍流特性的重要实验工作，并与目前的研究结果进行了比较。均匀砾石 ( d ₅₀= 4 cm) 在 15 cm 长的开放通道上随机排列成五层。床的地形和孔隙度在近床区域引起空间非均质流场，为了解决流 - 砾石 - 床界面上方和内部流动的空间非均质性，传统的时间平均方法由双平均（DA）补充概念。形式诱导剪应力 (FISS) 描述了获得总湍流应力的重要作用，发现它是发生在虚拟床层的 DA 雷诺剪应力 (RSS) 的 40%。此外，TKE 预算分布表明，TKE 生产、耗散和压力能量扩散在虚拟床层以上达到最大值，在虚拟床层以下急剧下降。重要的是，压力能量扩散在砾石波峰下方显示出负值。而且，