Correction factors to Pulse Boundary Model-measured flow velocity along simulated rill

Abstract

<abstract> <bold>Abstract.</bold> The water flow velocity along an eroding rill is of interests for understanding rill erosion hydrodynamics. However, the mean flow velocity is difficult to measured. Salt tracer method is a common used shallow flow velocity measurement, and corrected factors are used to get the mean velocity. A series of comparative flume experiments were conducted to measure the shallow water flow velocity, with a computerized electrolyte tracer method and dye tracer method. The experiments involved three flow rates (12, 24 and 48 L /min) and three slope gradients (5°, 10° and 15°). Five sensors were used to measure the solute transport processes at 30, 60, 90, 120 and 150 cm from the location where the salt solute was injected into the water flow. Centroid velocities, leading edge velocities, peak concentration velocities and velocities estimated by Pulse Boundary Model along the flume were computed for comparison purposes. The results showed that under different flow rates and slope gradients, the centroid velocities were 0.902-0.998 times of the velocities computed by the Pulse Boundary Model, and 0.819-0.975 times of the peak concentration velocities. The value of centroid velocity and peak concentration velocity got closer with increases in slope gradient and flow rate. The correction factor α_E were 0.530-0.629. The peak velocity u_p is more closely to the mean flow velocity than the centroid velocity <inline-graphic id=ID_66ac13b3-22f2-49ab-a750-a9f7021dc3b5 xlink:href=141899038_files/141899038-01.jpg/> under the set experimental condition. This method will help further study of the hydrodynamics in eroding rill.