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Beijing Forestry University (2019)

Aerodynamic Experimental Study on the Protective Effect of Sand Barrier

张帅;

Titre : Aerodynamic Experimental Study on the Protective Effect of Sand Barrier

Auteur : 张帅;

Grade : Doctoral Dissertation 2019

Université : Beijing Forestry University

Résumé partiel
As one of the main engineering measures for sand prevention and control,mechanical sand barrier has the advantages of simple layout,low cost,quick effect and long protection time.It plays an important role in the ecological management of sandland and the protection of key construction projects.However,currently,the main practice is mainly based on experience,and there is no corresponding standard to guide.In addition,the existing research focuses on the windproof performance of the sand barrier and ignores its sand accumulation capacity.Aiming at these problems,this study uses the typical sand barrier type of the northern sand barrier,the HDPE permeable net sand barrier and the Shaliu sand barrier as the research object,and analyzes the different configuration modes through the combination of field test and wind tunnel simulation test.The wind speed frequency,variogram,wind speed increase rate,effective protection area,sand wind speed and surface roughness of the sand barrier grid are discussed.The influence of grid size,porosity and barrier height on wind resistance and surface erosion of sand barrier is discussed.Based on the above research results,a new wind-proof benefit evaluation index—the surface layer displacement thickness is proposed to provide theoretical basis and practical reference for wind erosion protection work.The main conclusions are as follows :(1)The wind-proof performance of the grass-grid sand barrier is negatively correlated with the length of the grid ;the wind-proof performance of the HDPE-permeable sand barrier is negatively correlated with the porosity,and there is no consistent law between the edge length and the barrier height.Sexuality ;the wind-proof efficiency of Shaliu sand barrier is negatively correlated with side length and porosity,and positively correlated with barrier height.Under different wind speed conditions,the Shaliu sand barrier grid has the highest windproof performance,and the HDPE ventilation net sand barrier grid windproof performance is second.The grass square grid barrier grid has the lowest windproof performance.(2)The surface roughness of the grass-sand barriers decreases with the increase of the side length ;the surface roughness of the HDPE permeable net sand barrier and the Shaliu sand barrier increases with the increase of the barrier height.The displacement thickness of the boundary layer of the grass-square sand barrier decreases with the increase of the edge length ;the displacement thickness of the HDPE permeable net sand barrier and the Shaliu sand barrier boundary layer decreases with the increase of the side length and porosity,with the obstacle increases and increases.Compared with the surface roughness,the thickness of the boundary layer displacement can more accurately reflect the protective effect of the sand barrier.(3)The wind speed of the sand-sand barrier is negatively correlated with the side length ;the wind speed of the sand barrier of the HDPE permeable net is negatively correlated with the barrier height and porosity ;a maximum value occurs when the wind speed of the sand-sand barrier is 2m,the barrier is 20 cm high and the porosity is 0.3.This study comprehensively measures the sediment accumulation of sand barrier grids in different configuration modes,and visualizes them.At the same time,a new evaluation index—the thickness of the boundary layer displacement is proposed,which is not covered in the existing research..After effectively fixing the sand,how to carry out the restoration of the sandy ecosystem,optimize the combination of engineering measures and biological measures and chemical measures is the next research direction.In addition,the use of aerodynamics to explore the law of wind and sand movement from a microscopic perspective is also an urgent development direction

Mots clés : Wind Speed Acceleration Rate Field; Surface Erosion; Surface Roughness; Boundary Layer Displacement Thickness;

Présentation (CNKI)

Page publiée le 3 février 2021, mise à jour le 25 novembre 2021