Determination of correction factor of flow velocity on eroded rills by electrolyte tracer method with double injectors
Tingting Tao, Xiaoyan Chen, Jie Zhang, Tao Feng, Lingyong Kong, Fulin Luo, Wei Han
Abstract
Flow velocity is an important hydrodynamic parameter to study the rill erosion process, especially the erosion dynamic process. The dye tracer method is a common and simple method to measure the rill flow velocity. However, a correction factor is required to convert the surface flow velocity to the mean flow velocity. The reliable correction factor is vital to determine the mean flow velocity. A total of 144 flow velocities (surface and mean) were measured using electrolyte and dye tracers at the corresponding distances (4, 6, 12, and 16 m) under different inflow rates (6, 9, 12, 15, 18, and 21 L min−1) on eroded rills. Results showed that the electrolyte tracer method with double injectors can accurately measure the mean flow velocity under the condition of a long slope in the field. The Reynolds numbers varied between 1433 and 15864. And the correction factor α varied between 0.220 and 0.874 with an average value of 0.557. The correction factor was positively correlated with the rill width, depth, cross-sectional area, flow depth, and Reynolds number. Furthermore, the correlation coefficients between correction factor and hydraulic parameters were greater than those between correction factor and rill morphological parameters. Moreover, the correction factor could be predicted by the equation of inflow rate, Reynolds number, and slope length. The results verified the application of an improved double injector electrolyte tracer method on a long slope in the field, clarified the influence of rill morphology and hydraulic parameters on the correction factor, and developed a reference for mean flow velocity determined using the dye tracer method.