SCHMIDT NUMBER OF SAND SUSPENSIONS UNDER OSCILLATING GRID TURBULENCE
SCHMIDT NUMBER OF SAND SUSPENSIONS UNDER OSCILLATING GRID TURBULENCE
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DOI：
10.9753/icce.v33.sediment.20
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发表时间：
2012-10
期刊：
影响因子：
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通讯作者：
D. Buscombe;D. Conley
中科院分区：
文献类型：
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作者：
D. Buscombe;D. Conley
在波浪作用下泥沙悬浮的许多模型中，泥沙的扩散率与动量扩散率通过湍流施密特数的倒数相关联。这个数字的价值和参数化一直是许多研究的主题，但缺乏共识，导致特别调整湍流泥沙悬浮模型，显然没有什么物理理由。为了研究沉积物扩散率，我们进行了实验室实验，以产生仅梯度的沉积物扩散。由振荡网格产生的近各向同性湍流悬浮的沙子的浓度，连同详细的速度测量，被用来计算垂直剖面的施密特数的粒度和流动条件的范围。初步结果表明，动量扩散系数大于泥沙扩散系数，两者的比例与网格雷诺数。正在进行的工作将确定是否可以用沉积物和湍流之间的双向反馈来解释明显的粒度依赖性。
In many models of sand suspension under waves, the diffusivity of sediment is related to the diffusivity of momentum by the inverse of the turbulent Schmidt number. The value and parameterization of this number has been the topic of much research, yet a lack of consensus has led to ad hoc adjustments in models of turbulent sediment suspensions, with apparently little physical justification. In order to study sediment diffusivity we conducted laboratory experiments to generate gradient-only sediment diffusion. Concentrations of sand suspended by near-isotropic turbulence generated by an oscillating grid, together with detailed velocity measurements, were used to calculate vertical profiles of the Schmidt number with a range of grain sizes and flow conditions. Initial results suggest that momentum diffusivity is greater than sediment diffusivity, and that the ratio of the two scales with grid Reynolds number. Ongoing work will ascertain whether an apparent grain size dependence could instead be explained by two-way feedbacks between sediment and turbulence.