灌丛沙堆表面压力分布特征的实验研究

风成沙丘表面压力分布特征直接反映沙丘表面风蚀风积特点,因而是研究沙丘表面地貌过程的重要依据。依据风沙运动实验相似性理论,以新疆和田河流域实测柽柳沙堆为基础,按一定比例缩小制作成四组模型,选用起沙风速区间在6~14 m/s的5组不同风速分别对四组模型在风洞中作纯气流表面压力的模拟实验。结果表明,无植物覆盖的半球形沙堆和圆锥形沙堆的表面压力分布特征存在着较大差异,其中半球形沙堆迎风坡下部有较明显反射涡流,丘顶存在高压剪切气流区域,圆锥形沙堆则不存在这种风压变化,此外半球形和圆锥形沙堆两翼的高低压风蚀区域分布特点也不一致。人工“植物”引发的沙堆丘顶和背风坡区域表面风压的显著变化有利于截留沙尘、保护沙堆免受风蚀并促进沙堆增长。

Study on the Distribution Character of Surface Pressure of Nabkha in Wind-tunnel Imitative Experiment

The distribution character of the surface pressure on Aeolian dune can reflect directly character of deflation and wind deposition on the surface of the dune. Therefore, the surface pressure is the important basis of studying surface geomorphic process of dune. In this paper, according as similarity theory in wind - sand movement experiment, at the base of nabkha data surveyed in the basin of Hetian River in Xinjiang, four groups models of sand mounds are made according to the proportion. In the wind tunnel, the wind speed sector in 6 - 14m/s is selected, and five different velocities are used to observe the pure airflow surface pressure imitative experiment to four groups of models separately. The results of imitative experiments indicate that the distribution character of the surface pressure on semispherical and conical sand mound without plant is obviously different. There exist clearly reflected vortex at the bottom the upwind position of semispherical sand mound, and part of high pressure shear airflow on the top of semispherical sand mound. But, there is no the wind pressure change on the surface of the conical sand mound. Moreover, the distribution character of high and low pressure parts is no same. The visibly distribution change of the surface wind pressure which is caused by manmade vegetation on the top and at leeward slope makes for holding the dust and sand and protecting nabkhas from wind erosion to boost development of nabkhas.