Secondary Currents and Turbulence over a Non-Uniformly Roughened Open-Channel Bed
Secondary Currents and Turbulence over a Non-Uniformly Roughened Open-Channel Bed
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DOI：
10.3390/w7094896
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发表时间：
2015-09
期刊：
影响因子：
3.4
通讯作者：
T. Stoesser;R. McSherry;Bruño Fraga
中科院分区：
文献类型：
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作者：
T. Stoesser;R. McSherry;Bruño Fraga
对非均匀粗糙河床的流动进行大涡模拟 (LES)，以研究非均匀河床粗糙度对湍流驱动的二次流和湍流统计的影响。河床由粗糙和光滑的条带交替组成，其宽度与水深相对应。基于水力半径和体积速度的雷诺数为 34,000。使用实验数据成功验证了 LES。二次流和床层粗糙度对流向速度和二阶湍流统计有显着影响。湍流在粗糙条带上增强，在光滑条带上抑制。由于平流和湍流，发生了显着的横向动量传递。光滑条带上的床剪切应力比粗糙条带上的床剪切应力大约小四倍，这是由于近床低动量流体从粗糙条带输送至光滑条带以及高动量流体从表面向床层对流的结果。流向动量方程中最重要的项被量化并讨论了动量传递。
Large-eddy simulations (LES) of the flow over a non-uniformly roughened channel bed are carried out to study the effect of non-uniform bed roughness on turbulence driven secondary currents and turbulence statistics. The channel bed is comprised of alternating rough and smooth strips, the width of which corresponds to the water depth. The Reynolds number based on hydraulic radius and bulk velocity is 34,000. The LES are successfully validated using experimental data. The secondary flow and bed roughness have a significant effect on the streamwise velocity and second order turbulence statistics. Turbulence is enhanced over rough strips and suppressed over smooth strips. Significant lateral momentum transfer takes place due to both advection and turbulence. The bed shear stresses over the smooth strips are approximately four times less than over the rough strips a result of near bed low momentum fluid being transported from the rough strips to the smooth strips and high momentum fluid being convected from the surface towards the bed. The most significant terms in the streamwise momentum equation are quantified and discussed with regard to momentum transfer.