包兰铁路沙坡头段防护体系近地面流场特征

基于地形和流场实测，研究了包兰铁路沙坡头段铁路防护体系近地面流场沿NNW-SSE方向的变化．结果表明，由于地形变化以及人工植被和草方格的存在，防护带内等风速线沿风向呈逐渐变疏和抬高的趋势，各高度的风速总体上呈递减趋势，风速放大率为负；沙丘迎风坡风速放大率为正，流动沙丘迎风坡风速放大率高于固定沙丘迎风坡．沙丘背风坡2．5m高度内风速放大率总体为负．防护带内的固定沙丘背风坡气流通体减速，各高度的风速放大率全部为负，平均为一1．48％／m．防护带内地表空气动力学特征发生变化，其中沙丘迎风坡地表风速廓线接近于对数率；人工植被带地表空气动力学粗糙度显著高于流沙区．

Near Surface Air Flow Field Across the Shelterbelt of Shapotou Section, Baotou-Lanzhou Line

Based on field measurements, near surface airflow along the direction of NNW-SSD was studied across the shelterbelt of Baotou-Lanzhou line in Shapotou area. The results show isospeed lines in the shelterbelt become sparse gradually along the wind direction due to the changes of landform and vegetation; wind speed at each measured height exhibits a tendency of decreasing with minus wind speed-up coefficient. As the influence of landform is concerned, wind speed-up coefficient on windward slope of fixed dunes is positive, smaller than that on moving dunes; the values on leeside of the fixed dunes are negative as a whole with a mean value of -1.48%/m below 2. 5 m. Wind profiles on windward slopes deviate from but close to the logarithmic law. Derived from the wind profiles, aerodynamic roughness of artificial vegetational belt is remarkably higher than that of moving sand surface.