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首页> 外文期刊>European Journal of Mechanics, B. Fluids >Structure of turbulence over non uniform sand bed channel with downward seepage
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Structure of turbulence over non uniform sand bed channel with downward seepage

机译：非均匀砂床通道湍流结构，下渗漏

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Experimental investigations were carried out to investigate turbulent flow characteristics in non-uniform sand bed channels for both no seepage and seepage flow. Steady flows over non-uniform sand bed channel were simulated experimentally with downward seepage applied through the boundary. Measures of turbulent parameters such as velocity, Reynolds shear stresses, thickness of roughness sub layer and shear velocities were found increasing with seepage. The turbulent diffusivity and mixing length decrease in presence of seepage. The quadrant analysis suggests that the relative contributions of bursting events increased throughout the flow layer and the thickness of the zone of dominance of sweep event increases with seepage which is responsible for increment in bed material transport. The mean time of occurrence of ejections and sweeps in downward seepage are more persistent than those in no seepage. The analysis of third order moments states that an upward downstream flux of turbulent kinetic energy is observed over the near bed surface giving rise to sweeps with seepage. The turbulent kinetic energy fluxes increase in presence of seepage within the near bed flow. The increased in bed load transport with seepage associated with an increase in flow turbulence production corresponds with decrease in turbulent kinetic energy dissipation, pressure energy diffusion and turbulent diffusion. The traversing length decreases and size of eddies increases with seepage. (C) 2017 Elsevier Masson SAS. All rights reserved.
机译：进行实验研究，以研究非均匀砂床通道中的湍流特性，渗漏和渗流流动。通过基于边界施加的向下渗出模拟非均匀砂床通道上的稳定流动。发现诸如速度，雷诺剪切应力，粗糙度亚层厚度和剪切速度的湍流参数，渗透率增加。在渗漏的存在下，湍流扩散性和混合长度降低。象限分析表明，在整个流动层中增加了爆破事件的相对贡献以及扫描事件的优势区的厚度随着渗透而增加的渗漏，这是床型材料运输的增量。向下渗出的喷射和扫描的平均时间比没有渗漏的渗漏更持久。对三阶矩的分析指出，在近床表面上观察到湍流动能的向上下游通量，从而引起渗漏。湍流动能通量在近床流动内的渗漏存在下增加。随着流动湍流产量增加的渗出的渗流载荷的增加与湍流动能耗散，压力能量扩散和湍流扩散的减少相对应。横幅的长度减小和eddies的大小随着渗漏而增加。 （c）2017年Elsevier Masson SAS。版权所有。

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