坡面薄层水流流速研究

准确测量坡面薄层水流流速是分析和计算水动力学参数的前提,也是建立土壤侵蚀模型的基础。设置5个坡度(5°,10°,15°,20°,25°)和4个放水流量(2,4,8,16L/min),采用长12m、宽0.1m、高0.3m的水槽对坡面薄层水流流速进行了测量。通过记录水流前锋(前沿)流过水槽的时间计算水流的前沿流速,并采用染色剂示踪法和电解质脉冲法测量水流的平均表层流速和平均流速,与前沿流速进行对比。结果表明:试验的前沿流速为0.237~1.290m/s,且随着坡度和流量的增大呈增大趋势,流量对前沿流速的影响大于坡度的影响,前沿流速可以用坡度和流量的幂函数形式进行预测;将前沿流速与染色剂示踪法测得的平均表层流速和电解质脉冲法测得的平均流速进行对比,发现前沿流速与平均表层流速和平均流速均具有良好的一致性,但平均表层流速的数值远大于前沿流速,其相对误差为-15.018%^-27.825%,2种流速之间可以用系数0.758进行转换;前沿流速与平均流速的数值非常接近,且相对误差随着流量和坡度的增大逐渐减小,2种流速之间的转换系数为0.946。前沿流速与其他2种流速的经验系数主要受雷诺数的影响,所建立的等式可以较好地模拟2种经验系数。研究结果可为坡面薄层水流流速的研究提供参考。

Study on the Velocity of Shallow Water Flow on Slope

Accurate measurement of flow velocity of shallow water on slope is essential to analyze hydraulic parameters and establish soil erosion model. A flume of 12 m long, 0.1 m wide and 0.3 m height was used to measure the velocity of shallow water under five slope gradients (5°, 10°, 15°, 20° and 25°) and four flow discharges (2, 4, 8 and 16 L/min). By recording the time of flow front (front) passing through the flume, the leading edge velocity of flow was calculated. The average surface velocity and average velocity were measured by the dye tracer method and the electrolyte tracer pulse method, and compared with the leading edge velocity. The results showed that the leading edge velocity varied from 0.237 m/s to 1.290 m/s, and it increased with the increasing of flow discharge and slope gradient. The leading edge velocity was more sensitive to flow discharge than to slope gradient. The leading edge velocity could be predicted using a power function of slope gradient and flow discharge. By comparing the leading edge velocity with the average surface velocity measured by the dye tracer method and the average velocity measured by the electrolyte tracer pulse method, the results indicated that the leading edge velocity showed good consistency with the average surface velocity and the average velocity, but the average surface velocity was much larger than the leading edge velocity, and the relative error was -15.018% to -27.825%, and the conversion coefficient between the two velocities was 0.758. The leading edge velocity was relatively close to the average velocity, and the relative error decreased with the increasing of flow discharge and slop gradient, and the conversion coefficient between the two velocities was 0.946. The correction factor was more sensitive to Reynolds number than to flow discharge and slope gradient. The equations established in this study could be used to predict the correction factors. In general, the results of this study could be used as a reference to study the flow velocity of shallow water.