Unsteady two-dimensional orifice flow: a large-size experimental investigation

Orifice flows were used as water clocks since the Antiquity up to the 16-th century. Today orifices and nozzles are used for measuring discharges. Most works were conducted with steady flow conditions and there is little information on the unsteady flow pattern. In this study, the writers describe an experimental investigation of an unsteady orifice flow discharging vertically. The study was conducted in a large-size facility with a rectangular orifice (0.75-m by 0.07-m) discharging up to 1.2 m(3) in about 10 seconds. The study presents new information on the unsteady flow patterns, the discharge capacity and the velocity field in the reservoir. The results are compared with "classical" orifice flow results.