湿沙表面风蚀的动力过程与风干效应

Wind desiccation effect and dynamic process of wind erosion on wet sand surface

风干效应是影响湿沙表面风蚀传输过程的重要因素。为探究湿沙表面风蚀动力过程的作用机制,利用风洞装置模拟了低风速下湿沙表面风干过程。结果表明:(1)高湿度(>10%)湿沙表面的风干过程呈现三项式分布的“S”形变化特征,即定风速下表面湿度的下降速度呈现出前快中慢后快的特点,并且变化的转折点湿度为5.12%,证明了高湿度沙面风干过程开始加速与风蚀发生几乎同步。(2)低湿度下(<5.12%)风干速度及风蚀显著同步加快的湿度阈值(0.829%)接近于M1.5,湿沙表面风蚀可能与颗粒间水分存在形式相关。由此推断,湿沙表面的风干效应与风蚀过程存在互馈关系,即湿度降低至一定阈值,风蚀就会发生,同时风蚀过程会加速风干,此阶段的风干效应则呈线性变化特征。在实验获得的风干效应模型基础之上,建立了湿沙表面起动摩阻风速、风蚀模数随湿度变化的方程,这有助于了解湿沙表面风干过程中风蚀参数的变化特征。

Wind drying is a crucial factor influencing the wind erosion and transport processes on wet sand surfaces.To explore the mechanisms of wind erosion dynamics on wet sand surfaces,a wind tunnel device was used to simulate the wind drying process on wet sand surfaces at low wind speeds.The experimental results indicate that:(1)The wind drying process on wet sand surfaces with high humidity(above 10%)exhibits an"S"shaped change characteristic with a triexponential distribution.Under constant wind speed,the rate of surface humidity decrease shows a fast-slow-fast pattern,with a turning point humidity value of 5.12%.This value is very close to the threshold humidity value of 4%-5%for wet sand initiation found in existing studies,fully demonstrating that the acceleration of the wind drying process on high-humidity sand surfaces is almost synchronous with the occurrence of wind erosion.(2)Under low humidity(below 5.12%),the wind drying speed and wind erosion significantly accelerate synchronously at a humidity threshold of 0.829%,which is close to M1.5.Therefore,wind erosion on wet sand surfaces may be closely related to the form of water presence between particles.Thus,it is inferred that there is a feedback relationship between the wind drying effect and the wind erosion process on wet sand surfaces.When the humidity drops to a certain threshold,wind erosion occurs,and the wind erosion process accelerates wind drying.The wind drying effect at this stage shows a linear change characteristic.Based on the wind drying effect model obtained from the experiment,equations were established for the threshold friction wind speed and wind erosion modulus of wet sand surfaces as functions of humidity.This helps researchers understand the changing characteristics of wind erosion parameters during the wind drying process on wet sand surfaces and improves the related research on the wind erosion dynamics of wet sand surfaces.