Study On Mechanism Of Wind Velocity And Sediment Transport Increasing By Wind Guide Plant

The construction of moving dune is an important foundation in the prevention and control of land desertification.At present,the governance technology of small semi-fixed and moving dune has matured,but the technology of control the high moving dunes is relatively slow especially for poor natural conditions.We usually use large machinery to leveling the top of the high moving dune,but as to environmental constraints,the cost is relatively high.Using a new governance technology(wind guild plate),we find that the wind guide plate can change the rate and direction of the airflow.It can also effectively transform the near-surface wind flow field,alter the structure of the wind-sand flow and improve the capacity of the air carrying.With this method,we can control the high moving sand dunes with natural wind.Furthermore,the wind guide plate has the advantages of simple structure,small volume,and easy installation.In this paper,Fluent software was used to numerical simulation of the airflow field under the influence of 12 kinds of wind guide plates arrangement(15° ~ 70°).Through the field observation,different angles(15° ~ 70°)and tandem formation configuration mode(8 kinds)of air guide plate were set.The effect and influence range of the wind guide plate and the wind guide plate group on the transit airflow,sand transporting quantity behind the plate and wind-sand flow structure were analyzed.We also tested the effect of 45° wind guide plate on dune morphology in winter and compared the results of numerical simulation with field observation.The main conclusions are as follows:(1)The incident wind velocity had little effect on the relative range of strong wind area and weak wind area in the airflow field of Fluent software,but it had a great influence on wind velocity.The angle of the wind guide plate was the main factor to determine the influence degree of the wind guide plate on the wind velocity.With the increase of the angle,the effective acceleration zone and the wind velocity increased gradually,but the strong wind area at the top of the slope showed the opposite trend.(2)In Ulan Buh Desert,threshold velocity for sand movement on slope top of 10 m high moving sand dune was about 3.32m/s.With the height increase of windward slope,the threshold velocity for sand movement gradually increases(3)There was a low wind velocity area under the wind guide plant,which increased with the increase of the angle of the wind guide plate,but the wind velocity of the large angle deflector was higher than that of the small angle deflector at the outlet.The main acceleration effect of the wind guide plate was generally reflected in the vicinity of 1.5m behind the board.When the incident wind velocity was 2.28m/s,20°~45° wind guide plate can make the wind velocity at 1.5m behind the wind guide plant higher than the threshold velocity for sand movement,25° guide plate,40° guide plate and 45° guide plate for 3m at the board with the same effect,the plate at 4.5m after the same effect of the wind guide plate angle of 20°,25°,35°,40°,45° and 60°.And for both sides of the board,the wind guide plate also had a certain acceleration effect.(4)The wind guide plate increased the total sediment discharge behind the plate.The sediment discharge of medium angle of wind guide plant(30°~45°)had a higher lifting effect.20° ~ 50° of the small angle of the wind guide plate for the 1.5m after the plate to enhance the rate of sediment transport effect was high,and 40° ~ 60° angle of the wind guide plate 3m at the plate when the sediment transport rate to enhance the effect of higher,In the board after 4.5m was 25° ~ 35° small angle defender to enhance the effect of higher.The relationship between the sediment discharge and the height could be obtained by the method of piece wise fitting,and the correlation coefficient was generally above 0.98.Most of the wind guide plate in the leveling area could maintain the air flow on the surface sand material handling state,only 55° wind guide plate in the board 3m and 4.5m at the sand flow for the accumulation phenomenon.45° wind guide plate in the wind season for the dune shape had a significant impact,leveling the wind erosion phenomenon was obvious,but also in the accelerated dune wind level could also speed up the dune movement speed.(5)Tandem type wind guide plate groups were failed to improved the wind velocity step by step in the field test.The combination of the small angle front plate and the small angle rear plate produced some acceleration effect on the transit air flow,but the effective range was limited to the front panel outlet,the front side of the front panel and the top of the slope.Large angle rear plate although in the leveling area wind velocity higher than with the small angle back plate,but still below the control.(6)The results of the flow field of the single wind guide plate and the wind guide plate group had a high similarity with the numerical simulation results,and the wind velocity profile also had a high value of coincidence degree.Therefore,the simulation accuracy of the Fluent software for the wind guide plate is high.It could be used tosimulate the overall design of the wind deflector group by using the numerical simulation.It could simulate the wind guide plate for different working environment and explore the most suitable laying way.In short,even if in a weak wind environment,the rational distribution of the guide plate effectively increased the sediment discharge in the leveling area behind the plate and reduced the cost.In addition,the use of computer simulation design layout program could effectively improve the production efficiency and had a greater practical value for the high sand dunes control.