Drag Partition for Regularly-Arrayed Rough Surfaces
Drag Partition for Regularly-Arrayed Rough Surfaces
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DOI：
10.1023/a:1022119909546
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发表时间：
2003-05
影响因子：
4.3
通讯作者：
D. Crawley;W. Nickling
中科院分区：
文献类型：
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作者：
D. Crawley;W. Nickling
植被和其他粗糙度元素分布在表面上，可以提供显着的保护，防止风蚀，从流动中提取的动量，从而减少作用在表面上的剪切应力。一个理论模型haspreviously被提出来指定粗糙表面的阻力的分区，并预测所需的植被密度，以抑制风蚀。然而，模型参数尚未受到约束，模型的预测能力仍然不确定。进行了风洞研究，以测量一系列粗糙度密度下的阻力分配，并对模型进行参数化，以提高其潜在的适用范围。利用新型阻力天平分别测量了作用在粗糙元阵列和中间表面上的阻力。利用欧文传感器对表面剪应力的空间不均匀性进行了详细测量。数据与前人的结果一致，证实了模型的一般形式，阻力分区分析证实了参数定义β = CR/CS（式中CR和CS分别为粗糙元和表面阻力系数），平均表面剪应力与最大表面剪应力之间存在一个常数比例差，实验结果表明，表面剪应力不均匀性参数m的定义应该修改，虽然理论和物理原因，包括这个参数的模型似乎是有效的。m的最佳拟合值范围为0.53至0.58。
Vegetation and other roughness elements distributed across a surface can providesignificant protection against wind erosion by extracting momentum from the flowand thereby reducing the shear stress acting at the surface. A theoretical model haspreviously been presented to specify the partition of drag forces for rough surfacesand to predict required vegetation density to suppress wind erosion. However, themodel parameters have not yet been constrained and the predictive capacity of themodel has remained uncertain. A wind-tunnel study was conducted to measure thedrag partition for a range of roughness densities and to parameterise the model inorder to improve its range of potential applicability. The drag forces acting on bothan array of roughness elements and the intervening surface were measured independentlyand simultaneously using new drag balance instrumentation. A detailed measure of thespatial heterogeneity of surface shear stresses was also made using Irwin sensors. Thedata agreed well with previous results and confirmed the general form of the model.Analysis of the drag partition confirmed the parameter definition β = CR/CS(where CRand CSare roughness element and surface drag coefficients,respectively) and a constant proportional difference between the mean and maximumsurface shear stress was found. The results of this experiment suggest that the definitionfor m, the surface shear stress inhomogeneity parameter, should be revised, although thetheoretical and physical reasons for including this parameter in the model appear to bevalid. Best-fit values for m ranged from 0.53 to 0.58.