Study on Wind-tunnel Simulated Flow Pattern over Nabkha Dunes in Hetian River Basin, Xinjiang ( Ⅱ )
新疆和田河流域灌丛沙堆风洞流场的实验研究（Ⅱ）

In this paper,two models of nabkhas were made in 40:1 proportion in wind tunnel,according to similarity theory in wind-sand movement experiments,and on the base of nabkhas data surveyed in the Hetian river basin in Xinjiang.The airflow patterns over the semispherical and the conical models were simulated under pure wind with speed of 6,8,10,12,14 m\5s~(-1) separately.Experimental results showed that plants at the top of sand mounds can enhance the roughness of sand surface,reduce airflow energy and retard airflow to get over the sand mounds,and can eliminate the eroded region by strong wind that appeared commonly on bare sand mounds,and reinforce the influencing range of vortex at leeward side.Consequently,the structural characters of wind-sand flow in front of and behind the sand mounds must change.Therefore,the vegetation on sand mounds is benefit to hold flowing dust and sand,and to promote dunes to be accumulated.Vegetation has played a very important role in the course of nabkhas development.