Windproof effect of Robinia pseudoacacia forest in different forest belts

  Objective  Robinia pseudoacacia is a common used tree species for afforestation in China, which is widely planted in the estuary of the Yellow River. However, the area is vulnerable to strong wind invasion, and Robinia pseudoacacia root is prone to windfall due to its shallow root system. Therefore, a reasonable forest belt layout is of great urgency to reduce the maximum wind speed in the forest, avoid tree collapse and improve the wind-proof effect of Robinia pseudoacacia forest.

  Method  The study focused on the coastal Robinia pseudoacacia shelter forest as the research object. The Ansys Workbench platform was used to establish the calculation model of the wind field and Robinia pseudoacacia based on the two-way fluid-structure coupling technology, so as to discuss the windproof effect of Robinia pseudoacacia forest in different forest belts.

  Result  (1) Establishing the two-way fluid-structure coupling simulation model of Robinia pseudoacacia and the flow field, verified by field test data, the horizontal normalized wind speed error of the model was 13%, and the vertical normalized wind speed error was 6%, and when the wind vibration of the branches was relatively stable, the displacement error was 7 mm, the model had high simulation precision. (2) The simulation results showed that the first row of Robinia pseudoacacia had an obvious effect on reducing the wind speed. Under the working condition of fixed row spacing of 5 m, the wind speed will decrease in turn as compared with the previous row of Robinia pseudoacacia by 0.12 v_0 , 0.07 v_0 , 0.03 v_0 and 0.01 v_0 ( v_0 was the initial wind speed before the forest). (3) With the increase of row spacing, the overall windproof effect of the two adjacent rows of Robinia pseudoacacia gradually decreased. After the wind passed through the two rows of Robinia pseudoacacia with row spacing of 0.4H, 0.5H, 0.7H, 1.0H and 1.5H, respectively (H is the height of the tree), the difference between the two reduced wind speeds of the two rows of Robinia pseudoacacia was 0.15 v_0 , 0.12 v_0 , 0.07 v_0 , 0.04 v_0 and 0.01 v_0 , respectively. (4) The windbreak effect of staggered Robinia pseudoacacia forests was better than square arrangement, and the wind vibration amplitude of staggered branches of Robinia pseudoacacia was smaller.

  Conclusion  Different forest belt structures have a great influence on the windproof effect of Robinia pseudoacacia forest, it is an effective research method to evaluate the windbreak effect of different forest belt structures by numerical simulation technology, the results can provide scientific support for subsequent reasonable afforestation in this area.