Dehghani Amir Ahmad

Characteristics of subcritical flow on vertical drops with inverse slope downstream

Abstract

In this study, the hydraulics characteristics of vertical drops with inverse slopes at the downstream channel and subcritical flow in the upstream channel, such as energy loss, pool and downstream depths have been analyzed. Methods to predict flow characteristic and experimental procedures are considered in this study. It was found that the flow at the downstream channel could be either subcritical or supercritical flows. The pressure distribution produced by the plane impinging jet on the inverse slope was also examined. The experiments were conducted in the Hydraulics Lab, Department of Civil Engineering, Isfahan University of Technology. Two analytical models are also presented to evaluate drop characteristics. In the first models, several assumptions made by Rand, White and Gill in developing an equation for the energy loss at drops have been examined for this type of drops. In the second model, the falling jet is simulated using the theory of the submerged jet.

The experimental results of the drop length, the pool depth, the downstream depth and the energy loss have been compared to those of the predictions by the presented models. For the energy loss, the predictions of the first model for small slopes are closer to the experimental results. By increasing the inverse slope, the second model estimations are closer to the experimental results. For the pool depth, the second model estimations are closer to the experimental results. The estimated values of the pool depth are lower than the experimental data. This is because of the presence of the air in the pool which was not considered in the models.