Wind tunnel simulation of wind-sand transport characteristics over frozen dune surfaces
In winter,the soil beneath the top 10 cm of mobile dune surfaces in the Ulan Buh Desert undergoes freezing.Wind erosion of the dune surface layer exposes sections of the frozen soil.This results in a surface with frozen"bare patches"interspersed among dry sand layers,altering the windblown sand transport process.This study employs wind tunnel simulations to investigate the impact of the frozen layer on windblown sand transport patterns.It examines sand transport characteristics under different wind speeds and moisture gradients in three scenarios:non-frozen,frozen,and dry sand combined with frozen conditions.This study reveals how soil freez-ing affects sand transport.The results indicate that:(1)The sand transport rate per unit width of the aeolian sand source and the dry sand combined with frozen source increases exponentially with wind speed and decreases ex-ponentially with water content.Sand transport rate is strongly correlated with both wind speed and water content,following an exponential relationship with both factors.(2)Freezing reduces sand transport rate by 3％to 91％.When"bare patches"appear in the field,the sand transport rate decreases by 49％to 97％.Generally,the sand transport rate of dry sand combined with frozen is greater than that of aeolian sand before freezing,which is greater than that of frozen aeolian sand.(3)Before freezing,the sand transport rate of aeolian sandy soil de-creased with height,but after freezing,it first increased and then decreased with height.The relationship fol-lowed an exponential function.(4)During wind erosion,when the dry sand layer and frozen soil layer are inter-spersed,sand particles move from the dry sand bed to the frozen soil interface,causing changes in the sand bed surface.Saltation transport increases by approximately 18％,and the vertical distribution of sediment transport first increases and then decreases,conforming to a power function.The"trumpet effect"is observed at a height of 2 to 6 cm.When frozen"bare patches"appear on dunes in winter,windblown sand transport is inhibited,while the proportion of saltation in the wind-sand flow increases.
frozen layersand transport ratewind-sand flow structurewind tunnel experimentUlan Buh Desert
万方数据
维普
