雨滴击溅对薄层漫流的扰动能力与输沙特征

The Disturbed Ability and Sediment Transport of Shallow Flow under Raindrop Impact

采用人工模拟实验,对黄土雨滴击溅下坡面薄层漫流的流态、扰动能力和输沙特征进行了研究,结果显示:雨滴击溅作用下坡面薄层漫流的流态既不是层流也不是紊流,属于雨滴垂向作用下的高度混掺"扰动流";泥沙剥蚀量较无雨滴击溅薄层流剥蚀量显著增大,击溅雨滴直径越大,泥沙剥蚀量也越大,呈指数规律变化,表明雨滴击溅作用是薄层漫流泥沙剥蚀的主要动力。雨滴击溅对薄层漫流的扰动能力随着水流深度和雨滴直径比值的增大呈幂指数关系减小,当雨滴直径大于薄层漫流水深的2.5～3.0倍时,雨滴击溅对薄层漫流基本无扰动作用。基于雨滴击溅的主要影响因子,提出了缓坡坡面扰动系数预测方程,对研究薄层漫流泥沙流失预报模型具有重要意义。

By using the artificial rainfall, the shallow flow pattern, disturbed ability and sediment transport on slope surface were studied under the raindrop impact. The results showed the shallow flow pattern on slope surface under raindrop impact namely wasn＇t the laminar flow, also Wasn＇t turbulent flow, but be- longed to highly mixed disturbed flow under raindrop vertical impacts. The sediment detachment of shal- low flow under raindrop impact was obviously bigger than that under no raindrop impact, the bigger was the impacting raindrop diameter, the higher was the amount of sediment detachment, both assumes the in- dex rule change, indicating that the raindrop impacts were the main power to lead to the sediment trans- port on the shallow flow of slope surface. The disturbed abiiity of raindrop splashes to the shallow flow decreased with the exponential relations, as the flow depth and the raindrop diameter ratio increased. When the raindrop diameter is 2.5 to 3 times greater than the depth of shallow flow, the raindrop splashes to the shallow flow were basic non-disturbed function. Based on the major effect factors on raindrop spla- shes, this paper proposed a forecast equation for/the disturbed coefficient on gentle slope surface, which had an important significance to study the sediment forecast model on shallow flow.