A k-ε turbulence model based on the scales of vertical shear and stem wakes valid for emergent and submerged vegetated flows
A k-ε turbulence model based on the scales of vertical shear and stem wakes valid for emergent and submerged vegetated flows
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DOI：
10.1017/jfm.2012.113
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发表时间：
2012-06-25
影响因子：
3.7
通讯作者：
Cowen, E. A.
中科院分区：
文献类型：
--
作者：
King, A. T.;Tinoco, R. O.;Cowen, E. A.
通过水生植被的水流和输运的特点是长度尺度范围很广：水深（H）、植物高度（h）、茎直径（d）、单位体积植物锋面面积的倒数（a（-1））以及a变化的尺度。在平均垂直切变尺度（部分由a设定）和主干尾流尺度（由d设定）下均产生湍流。虽然来自这些源中的每一个的湍流通过能量级联消散，但是一些剪切尺度湍流绕过较低的波数，因为剪切尺度涡流确实对抗植物茎的形状阻力，将剪切尺度湍流转换为尾流尺度湍流。我们已经开发了一个k-mos模型来解释所有这些能量途径。该模型是校准对实验室数据床的刚性圆柱体在紧急和淹没条件下，并验证对一个独立的数据集从淹没刚性圆柱体和实验室数据集从冠层的活植被。新的模型优于现有的k-mills模型，其中没有一个包括d尺度，无论是在紧急刚性圆柱体的情况下，现有的k-mills模型完全崩溃，并在淹没的刚性圆柱体和活植物的情况下，现有的k-mills模型无法预测湍流动能对d的强烈依赖。新的模式是有限的冠层密度足够分散通量可以忽略不计。
Flow and transport through aquatic vegetation is characterized by a wide range of length scales: water depth (H), plant height (h), stem diameter (d), the inverse of the plant frontal area per unit volume (a(-1)) and the scale(s) over which a varies. Turbulence is generated both at the scale(s) of the mean vertical shear, set in part by a, and at the scale(s) of the stem wakes, set by d. While turbulence from each of these sources is dissipated through the energy cascade, some shear-scale turbulence bypasses the lower wavenumbers as shear-scale eddies do work against the form drag of the plant stems, converting shear-scale turbulence into wake-scale turbulence. We have developed a k-epsilon model that accounts for all of these energy pathways. The model is calibrated against laboratory data from beds of rigid cylinders under emergent and submerged conditions and validated against an independent data set from submerged rigid cylinders and a laboratory data set from a canopy of live vegetation. The new model outperforms existing k-epsilon models, none of which include the d scale, both in the emergent rigid cylinder case, where existing k-epsilon models break down entirely, and in the submerged rigid cylinder and live plant cases, where existing k-epsilon models fail to predict the strong dependence of turbulent kinetic energy on d. The new model is limited to canopies dense enough that dispersive fluxes are negligible.