黄河乌兰布和沙漠段沿岸不同高度典型沙丘风沙特征

为探究乌兰布和沙漠沿黄段典型沙丘的风速流场与风沙运移特征,以3座不同高度的典型沙丘为研究对象,对沙丘不同部位5个高度的风速流场、风速廓线、风速加速率及输沙量进行了测定。结果表明:(1)风速从沙丘迎风坡脚至背风坡坡脚呈现先增大后减小再增大的"S"型趋势,沙丘顶部风速最大,背风坡中部最小。(2)沙丘各部位风速的垂直变化与高度的对数值呈V=aln(z)+b线性变化规律,风速廓线斜率a由沙丘顶部向迎风坡脚与背风坡脚逐渐增大。不同高度沙丘的摩阻流速与粗糙度变化趋势不一。(3)沙丘发育尺度对沙丘迎风坡风速加速率影响明显,其沙丘发育尺度越大,对气流的反馈作用越强,迎风坡低层20cm风速加速率明显高于高层风速加速率;(4)沙丘不同部位0~100cm的输沙率随高度呈幂函数规律递减,输沙量主要集中在0~10cm内,但不均匀,大部分集中在0~4cm,且在距地高度约4~5cm处是相对输沙量不随高程变化的不变层。

Wind Velocity and Sand Flow Transport Characteristics of Different Height Typical Dunes in Ulan Buh Desert Along the Yellow River

Flow fields of wind speed and aeolian transport are concerned by scientists because of its basic position in desert research.We took 3 typical dunes with different heights as samples and measured flow fields of wind,wind profiles,velocity accelerations,sediment discharges of 5 heights of different parts.Results show that:(1) wind velocity is greater over the top of dune but lowest at central leeward and appeares to increase firstly and decrease later and increase eventually from dune windward slope foot to leeward slope foot,showing the tendency of ‘S' shape;(2) vertical changes of wind at different parts of dune and height changes of logarithmic follows the linear regression equation [V=aln(z)+b],slope of wind profile increases gradually from top of dune to slope foot of windward and leeward,friction velocity and roughness changes appear inconsistently;(3) wind velocity acceleration of low-rise (20 cm) is higher than high-rice;dune development scale impacts wind velocity acceleration of windward obviously,and feedback is significant with its growth;(4) sediment discharges of different dune parts within 0～ 100 cm show a uneven law of diminishing power function and concentrate in 0～10 cm,and distribute in 0～4 cm mostly.Relative sediment discharges are stable and do not transform with height changes.