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Effects Of Simulation Tree Bandwidth And Seasonal On Wind Flow Field In Wind Tunnel

Posted on:2019-02-09Degree:MasterType:Thesis
Country:ChinaCandidate:X L LiFull Text:PDF
GTID:2333330563455757Subject:Forestry
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The windbreak and sandbreak forest is kind of shelter forests for the purpose of preventing wind-borne sand damage and fixed flow.It is one of the important measures for combating desertification.We can improve protection benefits of windbreaks and sand-fixing forests by changing the configuration and structure of windbreaks and sand-fixing forests..It has important guiding significance for the deployment and construction of windbreak sand-fixing forests.In order to compare the wind speed,wind speed acceleration and windbreak effect of shelterbelt of different width.We study the change of the vertical space wind velocities in the condition of 7,10 and 15 m/s under the wind tunnel when the premise of belt distributions and vegetation coverage is 15%~25%.Then,we explored the windbreak effect of forest belts with different configuration modes and screened out forest belts with better windproof effects.The main outcomes of the researches are as follows:(1)For forest belts of different width,seasons changes,and tree species,it was divided into three layers: upper layer,middle layer,and lower layer.When the airflow reached the shelterbelt.The upper change layer was the least affected by the forest belt.The middle change layer was shielded by the canopy,which has the greatest impact,and was the formation of the wind shadow zone,and the level of change near the bed.The fluctuation ranges of different air layers in different forest belts were different.(2)The shelterbelts with different width,seasonal changes,and tree species had similarity in the acceleration rate of wind velocity.It was found that every forest belt formed flow field structure which was combined by the acceleration zone and the deceleration zone.With the increase of wind speed,the area of acceleration zone increased,and the area of deceleration zone decreased gradually,and it moved downwind.(3)At the experimental wind speed of 7,10 and 15 m/s,the windbreak efficiency of the forest belts decreased with the increase of wind speed.With the increase of height,the overall performance was the trend of increasing first and then decreasing.As the distance from the forest belt increased,the windproof performance decreased.The protective efficiency of forest belts were mainly reflected in the plant height,and the most obvious in the canopy layer.(4)At the experimental wind speed of 7 m/s,the horizontal variation trends of the three-line,six-line,and nine-line forest belts are similar and all fluctuate within the forest belt.The effective protection distances of the six-line and nine-line forest belts are the same and greater than one-line and three-line forest belts;Except for forest belts,the wind-resistance performance of leafy forests were higher than that of the leafless forest belt in the remaining locations.The effective protection distance of the leafy forest belt is also greater than that of the leafless forest belt;The windproof performance of type B forest belt was better than the type A forest belt before the forest belt 580 cm,and then it became the same.The effective protection distance of the type B forest belt is also greater than that of the type A forest belt.(5)At the experimental wind speed of 7 m/s,the windbreak effect of the six-line and nine-line forest belts are the same and greater than one-line and three-line forest belts.The wind protecting efficiency of the period with leave was more than the period without leave;The windbreak effect of the type B forest belt is larger than the type A forest belt.
Keywords/Search Tags:shelterbelt width, seasonal, species, windbreak efficiency, wind tunnel test
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