Study On Mechanism And Benefit Of Wing Bag Sand Barrier

The Wing Bag sand barrier is a kind of sand-fixing method combining dynamic and static.Its principle is to add a "wing" that can fluctuate with wind on the basis of the traditional bag sand barrier,which increases the resistance of sand wind,and slows down the sand wind by layers,so as to achieve the function of bottom bag sand fixation and wing wind elimination,and improve the effect of wind prevention and sand fixation.In this thesis,on the basis of comparing the wind and sand resistance benefits of the new wing-bag sand barrier with the traditional one by field measurement in Ulan Buhe Desert,the wind tunnel is used to simulate the change characteristics of airflow velocity field around the wing-bag sand barrier under different combination modes and the change characteristics of airflow profile with different gradients.The vertical distribution characteristics of sand flow before and after the wing bag sand barrier,sand blocking effect after the barrier and the change process of erosion and accumulation surface on the leeward side of typical sand barrier aim to screen out the best combination mode of wing bag sand barrier under different wind conditions and clarify the protection mechanism and sand prevention effect of wing bag sand barrier.The main research conclusions are as follows:(1)The air flow near the surface of different modes of sand barrier shows the trend of "s Table,decreasing,increasing and s Table".When the air flow is far away from the sand barrier,the air flow is in the state of laminar flow,and with the continuous movement of the air flow near the sand barrier,the lower air flow begins to rise due to interference,the wind speed lifting area is formed in front of the barrier,and a strong air flow area appears at the top of the sand barrier,and the air flow passes through the sand barrier.The wind speed decreases and there is a weak wind area or quiet wind area behind the barrier.As the air flow moves away from the sand barrier,the air flow gradually returns to the incoming flow state.This law does not change with the change of indicated wind speed,but there is an obvious difference in airflow inflection point.The airflow inflection point of Wing Bag sand barrier observed in the field is always about-5H,while that of bag sand barrier with the same specification(bottom bag)is about-2.5H.In wind tunnel simulation,the airflow inflection point of Wing Bag sand barrier is always about-8H.(2)With the increase of the indicated wind speed,the wind protection of single row and double row sand barriers gradually weakened,while the grid sand barriers were on the contrary;Under the three wind speeds,the effective protection range of single-row wing bag sand barrier is 2.99-6.50 times longer than that of bag-type sand barrier,and the wind speed reduction ratio is 10.50%-21.23% higher.The effective protection range of double-row wing bag sand barrier is 2.36-3.63 times longer than that of bag type sand barrier,and the wind speed reduction ratio is 22.87%-30.79% higher.Compared with the bag-type sand barrier,the effective protection range of grid wing bag sand barrier can be increased by 0.86-1.14 times,and the wind speed reduction ratio can be increased by14.09%-23.27%.Under the three layout modes,the sand transport amount of bag-type sand barrier at each point is greater than that of the wing bag sand barrier,and the total sand resistance index of the wing-bag sand barrier is obviously higher than that of the bag sand barrier,indicating that the sand resistance effect of the wing bag sand barrier is obviously better than that of the bag with the same bottom bag diameter.(3)Under the three wind speeds,the effective protection distance of 15×15double-row is the best(the protection range is greater than 44.27H),followed by 10×7.5double-row,and 12.5×3.8 double-row is relatively poor.Grid barriers show the best effective protection range under the three wind speeds,followed by "Hui type" and "Rizi type".With the increase of wind speed,the effective protection distance of all types of barriers decreases.The thickness of sand accumulation after typical wing bag sand barrier is grid sand barrier & GT.Double row wing bag sand barrier & GT;Single row wing bag sand barrier & GT;Bag shaped sand barrier.(4)When the wind speed of incoming flow is less than 9m/s,the combination mode of bottom bag and wing is recommended to use 10×5,12.5×3.8,12.5×9.4,12.5×12.5;Wing porosity is recommended to be 60%;It is recommended to use full-section and intermittent wing modes,10×5,10×7.5,15×4.5 and 15×7.5 when the incoming wind speed is 12m/s.Wing porosity is recommended to be 60%;Wing modes are recommended in full section and intermittent mode.When the inflow wind speed is12m/s,12.5×3.8,12.5×9.4,15×4.5,15×7.5;The wing porosity is recommended to be 60%or 80%.If the sand barrier length of a single wing bag is greater than 3m in the field,it is not recommended to use the whole section to prevent the whole section of the field wing from being buried by sand.Multi-stage and intermittent wing modes are recommended.It is recommended to use "back type" and "field type" wing bag sand barrier under multi-wind direction.