Stage–discharge equation for simple flumes with semi-cylinder contractions

Abstract

In this study, the outflow process of a simple flume with two semi-cylinders on either side of a rectangular channel having a zero slope was studied. This can be considered as one of the simplest form of contraction in a channel so it may have a broad applicability. From a practical viewpoint, the availability of a stage–discharge equation that can be reliably applied to a wide range of discharges would be of great practical importance. To extend the range of previous available data, new experimental runs were performed. Two new stage–discharge relationships were deduced: one general relationship by considering the contraction ratio and another relationship by neglecting the contraction ratio for a specified range of this variable. The proposed general stage–discharge relationship represents a novel equation to describe the flume outflow process. Other relationship can be used by neglecting the approaching channel width for the upstream Froude number ranges from 0.11 to 0.38. Compared with the available stage–discharge relationships, the results indicate that the proposed simple relationships can be reliably used for a wide range of discharges with acceptable accuracy.