Experimental Study of a Right-Angled End Junction between a Pipe and an Open Channel

Abstract

This paper presents an experimental study of a junction between a closed conduit and an open channel. This study was undertaken to explore hydraulic properties of outlets of subsurface drainage or sewage networks into an open air stream during flood events. Experiments were conducted in a laboratory flume, with a main rectangular channel joined at right angle to a lateral circular pipe. Both branches were supplied with independent flow rates and downstream water level was controlled by an adjustable weir. Several flow patterns were identified, combining free-surface and pressurized flows. Transitions between these flow patterns, as well as changes in water level or energy, in response to the modifications of experimental variables, were studied and could be linked to known properties of single channels, single pipes, and homogeneous junctions. Transitions between free-surface and pressurized pipe flow appeared to be strongly dependent on the whole set of experimental variables and the pipe longitudinal slope. This work contributes to a better knowledge of hydraulic and hydrologic key processes for point source discharging.