Research On Wind Speed Flow Field And Numerical Simulation Of Robinia Pseudoacacia Forest In Coastal Area

Wind disaster is one of the serious natural disasters.It has great damage to the growth and development of crops and the environment in the area affected by wind and sand.In recent years,the frequency of wind impacts has been high,disasters have caused human casualties and property losses to be huge.Coastal shelter forests,farmland shelter forests and other wind protection measures not only Wind damage can be reduced,and the changes in wind speed within the ecosystem can be adjusted to reduce or reduce the impact of wind disasters.Therefore,it is an important task to build a reasonable shelterbelt system according to local conditions in different areas and fully study the protective effect of shelterbelts,which is of guiding significance for the long-term healthy development of forest farms and farmland ecosystems.This paper takes the Robinia pseudoacacia forest belt at Junma Fifth Field,Gudao Town,Dongying City,Shandong Province as the main research object.Through a two-year field survey and forest investigation,a multi-directional comprehensive simultaneous measurement of wind speed and wind direction for multiple Robinia pseudoacacia forest belts reflects the protective effect of the shelterbelt.In-depth survey of the local ecosystem was conducted,and the temporal and spatial variation of wind speed around the forest belt of Junma Fifth Field was initially established,which provided a basis for exploring the internal mechanism of the protection effect of the shelterbelt,and combined with the fluid calculation module ANSYS FLUENT to apply the principles of modern fluid mechanics Numerical simulations are carried out on multiple Robinia pseudoacacia forest belts.The results of the study show that when the wind traverses the forest belt,from the windward side in front of the forest belt to the leeward side behind the forest belt,the wind speed first decreases and then slowly increases,but the relatively exceptions are low altitude positions close to the underlying surface and positions above the canopy height.When the wind speed passes through the forest belt,the horizontal direction shows a trend of first increasing and then decreasing.At the same time,the windward surface in front of the black locust forest,the middle of the forest belt and the leeward surface behind the forest belt all form different degrees of wind speed reduction areas.The forest belt has an obvious reduction effect on the wind speed flow field.When the wind passes through the forest belt,the windward area in front of the forest belt,the middle forest belt and the leeward area of the forest belt all form different degrees of wind speed reduction zones.The wind speed in the vertical direction near the ground and above the canopy of the forest belt is relatively weakly affected by the forest belt,and the height of the canopy and branches has a strong influence on the wind speed reduction.The location of the wind speed reduction zone will change as the wind speed changes.As the wind speed increases,the windproof effect of the forest belt will weaken and the effective windproof zone will decrease.The narrow forest belt has a better wind-proof effect.In this experiment,the 1.2H width forest belt has better protection effect than the 3H wide and 6H wide forest belts.The situation of the three forest belts is similar when the windward side of the forest belt moves toward the forest belt.However,the wind speed on the leeward side behind the forest belt varies greatly.Compared with two relatively wide forest belts,the 1.2H width forest belt has a smaller value of wind speed and a larger effective protection distance.This is the key to the protection effect of the shelter forest.Where.For the sample plot in this study,the Robinia pseudoacacia shelterbelt can not only effectively reduce the impact of natural disasters such as typhoons and cold waves,but also effectively protect the development of forest planting and tourism and entertainment industries.In this study,the wind speed did weaken after passing through the forest belts,but if the distance between the forest belts is longer,the wind speed will return to its original level.It can be seen from the contour change map of the wind speed flow field that,except for the weakened barrier effect of the forest belt,most of the air flow can be lifted through the forest belt,causing the upper airflow to be squeezed and the wind speed correspondingly increased.The effective protection distance of the Robinia pseudoacacia forest belt is 21 H,and the wind speed reaches the range of about 5H after the maximum protection distance,that is,the distance between the two forest belts is about 26 H,which can achieve better protection effects.The distance and density of the forests can be changed to reduce the wind speed and reduce the damage of strong winds to the farmland ecosystem and coastal shelter forest ecosystem.A reasonable design of the shelterbelt structure can provide a larger area of wind speed reduction(that is,the effective protection range)for farmland,which is of great significance to the protection of agricultural production.