Experimental Studies of Turbulence in the Surface Layer: Phase IV

9415003这项研究将通过在萨斯喀彻温省中北部的一片广袤的森林上进行和附加实验，评估表层湍流动能方程作为粗糙度、雷诺数和稳定性的函数的变化。为BOREAS实验临时安装在这个位置的26米高的塔提供了一个及时的机会来确定早期TKE研究的天气结果，这些研究在选定的“理想”野外地点也适用于更现实的地形。最近在两个相对平滑的地点(ZO 5厘米)进行的实验提出的问题将在粗糙得多的森林树冠(ZO 50厘米)上进行调查，使用经过验证的程序和为早期工作开发的设备。这些问题包括：a)湍流能量产生率和耗散率之差(耗散亏)随粗糙度雷诺数的增加而变化多少？B)高阶、湍流和压力输运项如何适应粗糙表面能量平衡的这些变化？以及c)von Karman常数是否随着粗糙度雷诺数的增加而继续减小到理论极限0.37？所获得的结果将被用来发展将TKE方程应用于实际地形上的表层流动的普遍项，并将被用来确定为森林上空的流动提出的各种尺度假设的准确性。

9415003 Frenzen This research will evaluate changes in the equation for turbulent kinetic energy (TKE) in the surface layer as a function of roughness Reynolds number as well as stability by conducting and add-on experiment over an extensive forest in north central Saskatchewan. A 26-m tower temporarily installed in this location for the BOREAS experiment offers a timely opportunity to determine weather findings of earlier TKE studies conducted over selected "ideal" field sites also apply over more realistic terrain. Questions raised by recent experiments over two relatively smooth sites (zo 5 cm) will be investigated over the much rougher forest canopy (zo 50 cm) using proven procedures and equipment development for the earlier work. These questions include: a) How much does the difference between rates of turbulent energy production and dissipation (the dissipation deficit) changes with increasing roughness Reynolds number? b) How do the higher-order, turbulence and pressure transport terms adjust to these changes in the energy balance over rough surfaces? and c) Does the von Karman constant continue to decrease with roughness Reynolds number to the theoretical limit of 0.37? Results obtained will be used to develop generalized terms for applying the TKE equation to surface layer flows over real terrain, and will be used to determine the accuracy of various scaling hypotheses proposed for flow over forests.