Flow regimes at grid drop-type dissipators caused by changes in tail-water depth

ABSTRACT

A comprehensive set of experiments was performed on grid drop-type dissipators in a rectangular open channel. The study aims to examine the adjustment and boundaries of different flow regimes as well as the variation of flow hydraulic characteristics downstream of a grid drop-type dissipator, caused by the gradual alteration of the tail-water depth. Considering an upstream subcritical flow approaching the grid drop-type dissipator, the tail-water depths were gradually changed until they exceeded the height of the vertical drop leading to a submerged flow condition. The flow regimes and hydraulic characteristics of the flow downstream of the drop were precisely inspected using flow visualization techniques. Results indicated that two key flow regimes, namely “bubble impinging jet flow regime” and “surface flow regime”, arise because of the changes made in the tail-water depth. Accordingly, empirical equations were derived for estimating the boundaries of flow regimes as well as the hydraulic characteristics of flow downstream of the grid drop-type dissipators.

Keywords:

• Flow regime
• grid drop-type dissipater
• model experimentation
• tail-water depth
• vertical drop