Hydraulics of clear and submerged overfall weirs with bottom circular-openings

Many standard weirs in Fayoum district (Egypt) have been perforated by 1, 2 or 3 pipes, to convey much water in the downstream direction. Measurements of discharge with these structures are complicated due to existence of the openings. In this research, an experimental study was carried out to investigate the flow over clear over fall weir with bottom circular opening. Nine weir models with different heights were tested in a horizontal laboratory flume. Three weir heights were used with each one, three pipes with different diameters were tested. The results of the flow over the weir with a circular opening were compared with those of the weir without an opening having the same dimensions. It was found that there is a large difference between them. Multiple regression equations based on energy principal and dimensional analysis theory were developed for computing the discharge over clear over fall weir with a bottom opening.