Modelling The Mean Velocity Profile In The Urban Canopy Layer
Modelling The Mean Velocity Profile In The Urban Canopy Layer
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DOI：
10.1023/a:1002785830512
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发表时间：
2000-10
影响因子：
4.3
通讯作者：
R. Macdonald
中科院分区：
文献类型：
--
作者：
R. Macdonald
一个简单的模式，最初推导出平均风速廓线在植被冠层流修改应用程序的阵列的三维表面障碍物（立方体），这可能是一个简单的城市typesurface的代表。结果表明，立方体阵列aren't太密集包装，预测exponentialvelocity profile提供了一个足够的适合thesapatially平均速度剖面（u（z））内的障碍物树冠。应用该模型的一组风洞数据允许评价的经验fittingparameter称为衰减系数。这与湍流长度尺度有关，可以通过操纵用于推导速度分布的梯度扩散模型的结果来发现。结果表明，湍流长度尺度随障碍物堆积密度的增加而减小。通过假设从冠层顶部的这个长度尺度到上覆惯性子层中的经典普朗特长度尺度的线性过渡，获得了简单障碍物射线内从地面到上覆半对数区域的全速度剖面的可接受模型。
A simple model originally derived for meanwind speed profiles in vegetative canopy flows ismodified for application to arrays ofthree-dimensional surface obstacles (cubes), whichcould be representative of a simple urban-typesurface. It is shown that for cube arrays that arenot too densely packed, the predicted exponentialvelocity profile provides an adequate fit to thespatially averaged velocity profile (u(z))within the obstacle canopy. Application of the model to a set of wind-tunnel dataallows for the evaluation of an empirical fittingparameter called the attenuation coefficient. This isrelated to the turbulence length scale, which can befound by manipulating the results of thegradient-diffusion model used to derive the velocityprofile. The results show a reduction of theturbulence length scale with increasing obstaclepacking density. By assuming a linear transition fromthis length scale at the top of the canopy to theclassical Prandtl length scale in the overlyinginertial sublayer, an acceptable model is obtained forthe full velocity profile within simple obstaclearrays, from the ground up to the overlyingsemi-logarithmic region.