阴山北麓耕地地表空气动力学粗糙度的试验研究

Aerodynamic Roughness from Coverage Surface in Farmland of Siziwang Town in Inner Mongolia

空气动力学粗糙度是表征地表空气动力学特性的重要参数。本文首先从空气动力学Navier—Stokes方程的理论模型出发,从理论上证明了空气动力学粗糙度与风速的关系,并得出了计算空气动力学粗糙度的表达式。又根据流体力学和极限理论,推导出同一床面空气动力学粗糙度随风速的增加而减小,并且减小的速度随风速的增加而减小。最后根据2004年11月和2005年4月16日在内蒙古四子王旗裸露耕地采集的风速数据,计算该地区冬季和春季地表空气动力学粗糙度的值并利用标准差进行分析,得出以下结论:地表的空气动力学粗糙度并不是一个定值,即使在同一个风速范围内,空气动力学粗糙度也是在一定范围内分布的,但是从总体上空气动力学粗糙度随着风速的增加是呈下降趋势的,各风速范围的平均空气动力学粗糙度与风速呈较好的指数负相关;150 cm、200 cm高度组合的风速比标准差最小,最稳定,因此得出测定裸露耕地冬季地表粗糙度的最佳高度是150 cm与200 cm;阴山北麓春季耕地地表空气动力学粗糙度的平均值小于春季;当u=0时,仅取决于下垫面的性质而与风速无关的粗糙度为S0,冬春两季S0分别为33.269 cm、23.969 cm,可见裸露耕地表面在春季抗风蚀能力较弱。

Aerodynamic roughness and displacement height are two important aerodynamic parameters of the vegetation coverage surface. The paper utilizes the numerical calculation methods and Mathematics Software Matlab6.5, simulating aerodynamics roughness length and displacement height of vegetation coverage surface of Siziwang town in Inner Mongolia. The present study simulated 8 vegetation density and 6 heights of vegetation surface＇s the relationship between wind velocity and friction velocity, aerodynamics roughness length and displacement height . The study compared anglicizing of the simulated results and the experimental data. The simulated results obtained showed that it could be a good reflection of kinetics parameters of the nature. The research obtained also additional some results of, for example, relationship between vegetation densities and aerodynamics parameters with the wind. All the results will contribute to the further study of the sandstorms movement mechanism on grassland.