Study On Wind-induced Response And Windproof Effect Of Trees Based On Two-way Fluid-structure Interaction

In this paper,the Robinia pseudoacacia plantation in Junma No.5 branch of Dongying City,Shandong Province,was used as the experimental site to test the wind speed and direction in Robinia pseudoacacia forest farm and determine the standard wood.Based on the L-system of fractal theory,the three-dimensional model of Robinia pseudoacacia was established by using Matlab and Ansys according to the height,height under branch,DBH and crown diameter of standard wood.Set 9 elastic constants of Robinia pseudoacacia and name it tree,which is the material property of the main and branch of Robinia pseudoacacia.Using AR method of linear filtering method and Matlab programming,taking measured wind speed as the initial wind speed,Davenport spectrum as the target spectrum,using Shiotami spatial correlation expression,the time history of fluctuating wind speed is obtained and added to the entrance of fluctuating wind field.The two-way fluid structure coupling numerical simulation of Robinia pseudoacacia and fluctuating wind field is realized on the Ansys Workbench platform.The results show that the measured value of wind speed is consistent with the simulated value,and the numerical simulation with standard k-? turbulence model can provide a good prediction for wind resistance of trees.Robinia pseudoacacia will block the wind and form an elliptical shelter area with low wind speed on the leeward side of Robinia pseudoacacia.The model of Robinia pseudoacacia makes wind flow around it,so two areas of increasing wind speed are produced around it.The main stem of Robinia pseudoacacia swings in the wind,and the displacement of the main stem is similar to that of the first branch.Under the action of fluctuating wind field,Robinia pseudoacacia will produce wind-induced response,in which the shear stress in YZ direction is the largest and the compressive stress in Z direction is the largest.The tensile stress of Robinia pseudoacacia in Z direction is the largest,and that in Y direction is similar to that in X direction.Tree height has a positive correlation with the anti wind effect of Robinia pseudoacacia.Increasing tree height can significantly increase the anti winddistance of Robinia pseudoacacia,and the degree of thinning has a negative correlation with the anti wind effect of Robinia pseudoacacia.Reducing the degree of thinning of Robinia pseudoacacia can reduce the wind speed at the leeward position of Robinia pseudoacacia,and the better the anti wind effect of Robinia pseudoacacia.With the increase of the number of Robinia pseudoacacia lines,the larger the sheltered area of low wind speed is,the more obvious the weakening effect of wind speed is.Although increasing the number of lines can effectively increase the wind distance of Robinia pseudoacacia,but also can greatly reduce its wind efficiency.Reducing the row spacing of Robinia pseudoacacia can get better windproof effect.The two lines of Robinia pseudoacacia with a distance of3 meters can provide a whole shelter area with low wind speed.When the row spacing increases to more than 15 meters,the two rows of Robinia pseudoacacia need not be regarded as a whole,but can be approximately regarded as two separate rows of Robinia pseudoacacia.The results show that the linear distribution pattern can obtain a wide protection area,while the staggered distribution pattern has a longer protection area.The wind protection effect of the staggered locust forest is better than that of the rectangular arrangement.