Subjects: Biology >> Botany submitted time 2023-05-30 Cooperative journals: 《干旱区研究》
Abstract： The purpose of this study was to provide a theoretical basis for the rational selection of different vegetation types for wind and sand control in arid and semiarid areas. Fluent software was used to numerically simulate the flow field around three types of typical strains (altar-shaped, shuttle-shaped, and broom-shaped) of scrub to analyze the influence of different plant forms on wind and sand flow and verify the results using existing wind tunnel tests. Results showed that (1) The flow field around the three types of plants can be divided into five zones, and three eddies exist behind the plants. Due to the intensity of the eddies, during the initial phase of sand accumulation, shuttle- shaped and broom- shaped plants accumulated sand primarily at 6-7 H after the plant, whereas altar-shaped plants accumulated sand at 3 H. (2) Affected by the height layer of the maximum profile area of the plant, the minimum wind speed at 1 H after the three types of plant shrubs appeared at heights of 0.3, 0.4 m, and 0.8 m, and the optimal protection range of height was 0.2- 0.4 m, 0.3- 0.6 m, and 0.8- 1 m, respectively. The aerodynamic roughness of the three plant types decreased gradually, and the roughness of the altar-shaped plants was significantly higher than that of the other two plant types. (3) All three types of strains could effectively reduce wind speed in the range of -2-10 H. The wind protection benefits in the near-surface area after the strains are altar-shaped > shuttle-shaped > broom-shaped the wind protection benefits in the midaltitude area all decrease with increasing plant distance. (4) At T = 10 s, the total duration of sand accumulation around the three plants was 8.5 H, 6 H, and 4.5 H, respectively, and wind erosion existed to different degrees at 5- 5.5 m and 4.5-6 m from the entrance for Haloxylon ammodendron and Calligonum mongolicum, respectively. Compared with other plants, Nitraria tangutorum exerted a better sand-blocking effect. Hence, it is recommended to combine N. tangutorum with H. ammodendron and C. mongolicum in the construction of wind and sand fixation projects, so that the sand- blocking property of N. tangutorum can be effectuated, and the better windblocking effect of H. ammodendron and C. mongolicum can be utilized at medium and high altitudes.
Subjects: Biology >> Botany submitted time 2022-12-20 Cooperative journals: 《干旱区研究》
Abstract：
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 10 m∙s - 1 , the windproof efficiency at a height of 0.3 m within a distance of 5.3 m behind the plant decreases from 40% 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.
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