三种不同床面近地层湍流输送特征

为了深入理解土壤风蚀发生机制,利用风洞实验风速廓线资料,采用空气动力学方法,计算了干旱、半干旱地区不同类型地表近地层湍流输送随风速以及地表性质的变化特征.结果表明:地表越粗糙,风速越大,湍流输送越强,且湍流输送强度与地面粗糙元密度有关.

Characteristics of Turbulent Transmission near Ground Surface over Three Different Beds

Wind is one of the exogenic forces shaping landscapes.Wind erosion is one of the main geomorphologic processes in arid,semiarid and cold-alpine regions.Except forming various wind-eroded landforms,wind erosion can result in soil erosion,increase of land surface roughness,land degradation and desertification.Moreover,wind erosion can produce atmospheric aerosols in a big quantity to pollute air and affect directly or indirectly the atmospheric radiation balance and even global climate change.Wind erosion is caused by both natural and artificial factors.In order to thoroughly reveal the occurrence mechanism of wind erosion,in this paper,the data of the wind profile from wind tunnel experiments are used to study the characteristics of turbulent transmission with wind speed over the vegetation-uncovered sandy bed,gravel bed and vegetation-gravel bed in arid and semiarid regions by using aerodynamic methods.The results are as follows:(1) The turbulent transmission intensity is increased with the increase of free wind speed,sand grain size and land surface roughness;(2) The turbulent transmission intensity is closely related to the density of roughness elements,it is increased with the increase of roughness element density when the density is low,and its change curve becomes gentle when the density reaches a certain value.The study results have certain reference and guiding significance for further researching the relationship between the turbulent transmission and turbulent energy dissipation near the ground surface and for revealing the wind erosion mechanism.