几种典型戈壁床面风沙流特性比较

通过不同材料覆盖的戈壁床面风沙流特性风洞模拟实验,发现对于棱角状砾石戈壁床面,地表动力学粗糙度随风速的增加而增加;而卵石床面,地表动力学粗糙度随风速的增加呈减小趋势。戈壁床面风速随高度的分布同样满足对数规律,棱角状砾石床面对风速的减弱程度相对于卵石床面更趋于显著。沙粒与戈壁床面棱角状砾石发生碰撞时其起跳高度增大,引起含沙量随高度分布不再满足流沙地表的指数衰减规律,而呈“象鼻效应”,出现拐点。戈壁地表输沙率与风速服从幂函数关系,但其幂指数远大于流沙地表。输沙率与风速之间幂函数关系中幂指数的取值主要受控于地表粒度组成。

Characteristics of Sand-blown Flow over Simulated Gobi Surfaces

The goal of this paper is to reveal the characteristics of sand-blown flow over Gobi surfaces based on wind tunnel simulation experiments.Results are shown as follows.Aerodynamic roughness increases with increase of wind speed on simulated gravel Gobi surface,but deceases with increase of wind speed on simulated pebble Gobi surface.Wind speed varies logarithmically with height over simulated Gobi surface.The weaken effect of simulated gravel Gobi surface on wind speed is more obvious than that on simulated pebble Gobi surface.Sand transportation over simulated Gobi surface does not follow the exponential decreasing law with the increase of height as over mobile sand surface because the bounced angle of sand grain will increase when it collides with gravel on Gobi surface,and appears an inflexion and takes on "trunk-shaped".Sand transportation rate presents a power-functioned correlation with wind speed,but its power exponent is far greater than that on mobile sand surface.The value of the power exponent mainly depends on particle size composition of underlying surface.