黄河中游多沙粗沙区坡面薄层水流水动力学特性

通过人工模拟降雨试验对黄河中游多沙粗沙区沙黄土坡面薄层水流水动力学特性进行了试验研究,取得了以下结果:(1)不同坡度不同降雨强度条件下,坡面薄层水流流速随降雨历时的增加而增大,可用对数方程很好地描述,薄层水流流速与雨强和坡度呈正相关关系;(2)不同坡度不同降雨强度条件下,坡面薄层水流的平均水深随降雨强度的增加整体警平稳增长趋势,其变化过程均可用幂函数方程描述,而平均水深与坡度呈负相关关系;(3)不同坡度不同降雨强度条件下,坡面流雷诺数随降雨历时的持续整体呈递增趋势,雨强对雷诺数的影响较坡度更为显著,薄层水流不属于传统意义上的层流,而是处于层流失稳状态;佛汝得数随降雨历时的变化范围基本上都大于1,且随着降雨历时的延长而稳步递增,坡度对佛汝得数的影响比雨强更为显著,试验中薄层水流基本处于急流状态;(4)不同坡度不同降雨强度条件下,坡面流阻力系数随降雨历时的持续皆呈递减趋势.

Hydraulic Properties of Shallow Flow in Coarse Sediment Region of Yellow River Middle Reaches

Based on simulated rainfall experiment,hydraulic properties of shallow flow in the coarse sediment region in the middle reaches of the Yellow River were studied. The following results were obtained:(1) Shallow flow velocity increased with rainfall process under different rainfall intensities and slope gradients and it can be described with logarithmic equation. Shallow flow velocity was positively related to rainfall intensity and slope gradient. (2) The averaged shallow flow depth increased steadily with rainfall intensity under different slope gradients and it can be described with power equation. The averaged shallow flow depth was negatively related to slope gradient. (3) Under different rainfall intensities and slope gradients,Reynolds number of shallow flow increased with rainfall process. The influence of rainfall intensity on Reynolds number was more significant than slope gradient. Shallow flow was not the traditional laminar flow but in the state of instability. Froude number increased steadily with rainfall process,with the number being above 1. The influence of slope gradient on Froude number is more important than rainfall intensity. Shallow flow in the experiment was in the state of supercritical flow. (4) The resistance coefficient of shallow flow decreased with rainfall process under different rainfall intensities and slope gradients.