Threshold criteria for incipient sediment motion on an inclined bedform in the presence of oscillating-grid turbulence
Threshold criteria for incipient sediment motion on an inclined bedform in the presence of oscillating-grid turbulence
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DOI：
10.1063/1.4774341
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发表时间：
2013-01-01
影响因子：
4.6
通讯作者：
Munro, R. J.
中科院分区：
文献类型：
--
作者：
Wan Mohtar, W. H. M.;Munro, R. J.
在这里，我们报告了实验室实验，以研究在存在振荡网格湍流的情况下初始沉积物运动的阈值标准，其中床坡以水平线和沉积物的静止极限之间的角度倾斜。使用一组九种单分散沉积物类型，其尺寸范围通常与水力平滑或过渡状态相关。使用二维粒子成像测速仪获得了网格和床型表面之间区域的（湍流）流体速度场的测量结果。速度数据的统计分析表明，由于近床区域能量从法向速度分量向切向速度分量的净转移，湍流具有各向异性结构，并且与二次平均流相比，波动占主导地位。水平床形的沉积物阈值标准与标准屏蔽曲线进行了比较，发现与标准屏蔽曲线具有良好的定性一致性。对于非水平地床形态，发现床层移动性随着床层坡度的增加而增加，并且基于简单的力平衡论证，将阈值标准与先前报告的理论模型进行了比较。 (C) 2013 年美国物理研究所。 [http://dx.doi.org/10.1063/1.4774341]
Here, we report laboratory experiments to investigate the threshold criteria for incipient sediment motion in the presence of oscillating-grid turbulence, with the bed slope inclined at angles between the horizontal and the repose limit for the sediment. A set of nine mono-disperse sediment types was used with size ranges normally associated with either the hydraulically-smooth or transitional regimes. Measurements of the (turbulent) fluid velocity field, in the region between the grid and bedform's surface, were obtained using two-dimensional particle imaging velocimetry. Statistical analysis of the velocity data showed that the turbulence had a anisotropic structure, due to the net transfer of energy from the normal to the tangential velocity components in the near-bed region, and that the fluctuations were dominant compared to the secondary mean flow. The sediment threshold criteria for horizontal bedforms were compared with, and found to be in good qualitative agreement with the standard Shields curve. For non-horizontal bedforms, the bed mobility was found to increase with increasing bed slope, and the threshold criteria were compared with previously-reported theoretical models, based on simple force-balance arguments. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4774341]