干枯骆驼刺对风沙流场影响的数值模拟研究

Numerical simulation study on the influence of dry Alhagi camelorum on the wind-sand flow field

植物固沙是荒漠地区防治风沙灾害的重要措施之一,骆驼刺(Alhagi camelorum)作为典型荒漠植物具有重要的应用价值。利用fluent软件对30 cm高度干枯骆驼刺附近的流场进行数值模拟,分析风速特征和积沙特征,并加以野外试验验证。结果表明:(1)植株附近流场大致可分为遇阻减速区、抬升加速区、紊流减速区以及恢复区。植株后会形成微弱的涡流,涡流的回流区高度与距植株远近有关,但整体低于0.14 m。(2)当风速为6 m·s^(-1)时,植株主要影响0.6 m高度以下的水平风速。植株后一定距离内的水平风速随高度增加不在呈现严格的对数分布,而是存在2个极小值,并在0.3~0.6 m高度范围内以较大的加速度快速增大。(3)植株的防风效率整体呈现出随风速增大而减小的规律,且该现象随高度增加愈加明显。当风速由6 m·s^(-1)增大至10 m·s^(-1)时,株后5.3 m范围内,0.3 m高度处的防风效率由40%减小至16.56%。(4)植株附近的积沙因风速的不同具有差异,当风速较小时,积沙主要集中在前方植株附近以及植株之间,随着风速的增大,积沙后移。

One of the important measures to control sand disasters in western desert areas is sand fixation by plants.As a typical desert plant,Alhagi camelorum has important application value.Based on the flow field in the spring,30 cm of dry Alhagi camelorum was the object of research in this paper.To analyze the characteristics of wind speed and sand deposition,a numerical simulation was used via the fluent and field tests.The results were as follows:(1)the wind-sand flow can be roughly divided into the areas of blocked deceleration,lifting acceleration,turbulent deceleration,and recovery when going through the plant.A weak vortex forms behind the plant,and the height of the recirculation region is related to the distance from the plant.However,they are less than 0.14 m.(2)When the wind speed is 6 m·s^(-1),plants at a height of 30 cm mainly affect the horizontal wind speed below a height of 0.6 m.The horizontal wind speed at a certain distance behind the plant no longer presents a strict logarithmic distribution with height,but there are two minima,and the acceleration increases rapidly in the height range of 0.3-0.6 m.(3)The windproof efficiency of plants decreases with the increase of wind speed,and this phenomenon becomes more and more obvious the height increases.When the wind speed increases from 6 to 10m·s^(-1),the windproof efficiency at a height of 0.3 m within a distance of 5.3 m behind the plant decreases from40%to 16.56%.(4)The sand accumulation near the plant is different due to the different wind speed.When the wind speed of the incoming flow is low,sand accumulation is mainly concentrated near the front of the plant and within the range between plants.As wind speed increases,sand accumulation moves backward.