Characteristics of subcritical flow over vertical drops with sloping aprons

In this investigation, characteristics of vertical drops with subcritical flow at the upstream channel and sloping aprons at the downstream channel have been studied experimentally.  Flow characteristics such as pool depth, downstream depth, and energy loss have been measured.  Two physical models of 0.41 and 0.21 m height were built and the inverse slope was set at 5°, 10° and 15° degrees. Experimental data were compared with the previous investigators’ results for horizontal downstream channels.  A method is presented to estimate flow characteristics.  It was shown that the values of the relative pool depth for sloping aprons are larger than those with a horizontal downstream channel.  It was found that the values of the relative downstream depth for sloping aprons are slightly larger than those with a horizontal downstream channel. Experimental results show that the relative energy loss increases by increasing the angle of the invert and the maximum increase is for the 5° degree slope. Predictions for the pool and downstream depths agree with the experimental data, but the differences between the predictions and the experimental results of the relative energy loss are significant.