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低覆盖度植被的防风固沙效果一直是防沙治沙工程中的关键问题。在风速为10 m.s-1和15 m.s-1的风洞实验条件下,模拟研究了覆盖度为20%的行带式分布和随机分布的乔木固沙林的风速流场和防风效果。结果表明:①在水平空间上,随机分布和行带式模式都形成了风影区和风速加速区相互组合的复杂水平流场结构,其中,随机分布要比行带式模式的流场结构更加复杂。②在垂直空间上,林冠下近地面(1.2 cm以下)风速都有微弱的增加,1.6～20 cm高度行带式模式内风速均有所减小,而随机分布模式风速变化无明显规律。③随机分布模式中两株植株相互组合时,不仅在植株两侧出现风速加速区,同时在两植株间出现风速加速区,出现“狭管增速效应”。
The windbreak and sand fixation of low coverage vegetation has always been a key issue in desertification prevention and control. Under wind tunnel experiments with wind speeds of 10 m s-1 and 15 m s-1, the wind flow field and windbreak effect of arborous and arbor-shrub with 20% coverage were simulated. The results show that: (1) in the horizontal space, both the stochastic distribution and the belt-line model form a complex horizontal flow field structure in which the wind-shadow zone and the wind-speed acceleration zone are combined with each other, wherein the random distribution is more more than the flow field structure complex. (2) In the vertical space, the wind speed near the ground under the canopy (below 1.2 cm) increased slightly. The wind speed in the belt mode with the height of 1.6-20 cm decreased but the wind speed in the random distribution mode had no obvious regularity. ③ When the two plants were combined with each other in random distribution mode, not only the wind speed acceleration zone appeared on both sides of the plant, but also the wind speed acceleration zone appeared between the two plants.