Flow regimes and energy dissipation of multiple slit-type energy dissipaters.

Li Yao, Wen-li Yang

Monday 29 june 2015

17:33 - 17:36h at Africa (level 0)

Themes: (T) Water engineering, (ST) Experimental facilities and instrumentation, Poster pitches

Parallel session: Poster pitch: 3F. Engineering - Instrument

Energy dissipation downstream of high dams is a serious concern. A slit-type energy dissipater (STED), thanks to simple geometry and high energy dissipation ratio, has been widely used in many hydropower projects. In the present paper, a multiple slit-type energy dissipater (M-STED) was developed, which adopted the functions of both STED and dentated sill energy dissipaters. In the vertical direction of the M-STED, some slits are placed so that the flow is divided into several layers when it leaves the outlet of the M-STED. Thus, the energy dissipation is enhanced due to the effects of the turbulence between the layers and of the increasing air entranment to the flow. Two types of those physical models were designed with nine cases, and the hydraulic characteristics were experimentally investigated on the basis of theoretical analises. The main contents include the observation and classification of the flow regimes, the variations of the energy dissipation ratio with the geometric and hydraulic parameters, and the comparisons of the behaviour of both STED and M-STED. The results present: (1) the critical conditions of the flow regime conversion for working, critical and non-working flow regimes, which are related to the flow Froude number Fr, slit number n and slit width a1, and the working flow regime could be formed if large Fr or much more n and small a1; (2) the effects of the flow regimes on the energy dissipation ratio, clearly, which is dominated by the geometric and hydraulic parameters; and (3) under the present conditions, the increase of energy dissipation of about 5% comparing with the STED.