Turbulence Modulation by Suspended Sediment in a Zero Mean‐Shear Geophysical Flow
Turbulence Modulation by Suspended Sediment in a Zero Mean‐Shear Geophysical Flow
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零平均剪切地球物理流中悬浮沉积物的湍流调制
DOI：
10.1002/9781118527221.ch20
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发表时间：
2013
影响因子：
11.4
通讯作者：
M. Fay
中科院分区：
文献类型：
--
作者：
S. Bennett;J. Atkinson;Yinting Hou;M. Fay
悬浮泥沙输运对地球物理湍流的影响在文献中一直存在争议。然而，在结果和通常用于区分湍流调制发生的标准的解释中仍然存在模糊性，特别是在实验明渠流动中。为了解决这些问题中的一些，悬浮泥沙对流体湍流的影响进行了研究，使用一个标准的混合箱，其中一个单一的振荡网格被放置在地板附近的设备。使用粒子图像测速法对给定网格振荡频率下的箱内流动条件进行量化，其中使用荧光示踪粒子来区分流体相，并仔细监测这些流体流动条件的变化，因为引入了跨越供应限制到运输限制悬浮液的石英密度沉积物浓度。悬浮泥沙的影响的大小的流体湍流在这个地球物理流是明确的和显着的。随着悬浮泥沙负荷在给定振荡频率下浓度的增加，混合箱内流体湍流的幅度显着和系统性地降低。虽然在同一流场中同时观察到湍流增强和抑制，但悬浮泥沙负荷的总体效果是降低流体湍流、总动能和能量耗散率。这里有人认为，湍流动能的减少是由于这种能量转移到悬浮的沉积物。这里提出的经验证据明确地表明，在悬浮泥沙的存在下，流体湍流可以显着减少，这些观察结果应该适用于广泛的泥沙地球物理流。
The effects of suspended sediment transport on turbulent geophysical flows have long been debated in the literature. Yet there remains ambiguity in the results and in the interpretation of criteria commonly employed to discriminate the occurrence of turbulence modulation, especially in experimental open‐channel flows. To address some of these issues, the effects of suspended sediment on fluid turbulence were investigated using a standard mixing box where a single oscillating grid was placed near the floor of the apparatus. Flow conditions within the box for a given grid oscillation frequency were quantified using particle image velocimetry where fluorescent tracer particles were used to discriminate the fluid phase, and changes to these fluid flow conditions were carefully monitored as concentrations of quartz‐density sediment spanning supply‐limited to transport‐limited suspensions were introduced. The effects of suspended sediment on the magnitude of fluid turbulence in this geophysical flow were clear and significant. As suspended‐sediment loadings increased in concentration for a given oscillation frequency, the magnitude of the fluid turbulence within the mixing box decreased markedly and systematically. While both turbulence enhancement and suppression were observed simultaneously in the same flow field, the overall effect of the suspended sediment load was to decrease fluid turbulence, total kinetic energy, and the rate of energy dissipation. It is contended here that the reduction in turbulent kinetic energy in the flow was due to the transfer of this energy to the sediment in suspension. The empirical evidence presented here demonstrated unequivocally that fluid turbulence could be significantly reduced in the presence of suspended sediment, and these observations should be applicable to a wide range of sediment‐laden geophysical flows.