DISCHARGE CHARACTERISTICS OF UNDERSLUICE GATES

Abstract

Sluice gates are widely used for measuring, controlling and regulating the flows in hydraulic structures. They are used in different locations. Some times they are used on horizontal floors as a discharge measuring device, whereas in case of diversion structures, they are placed over a raised sill for diverting water from the main river to canals for purposes of irrigation, power generation etc. The discharge characteristics of sluice gates placed on horizontal floors have been investigated by Henry(1). Whereas for sluice gates placed on raised sill, these characteristics have been studied by Ranga Raju and Visavadia (4). However, a different situation arises when they are provided in the undersluice portions of Barrages. The downstream faces of undersluice bays are invariably sloping and the upstream floor is horizontal which is kept at the minimum river bed level. Further to prevent the entry of sediment into the offtaking canal/excluders are provided covering some bays of undersluices. The discharge characteristics of sluice gates placed in this situation are not known, it was therefore thought desirable to take up this study. Experiments were carried out to study the discharge characteristics of undersluice gates with and without silt excluder. Three downstream slopes and two heights of silt excluder were used. For undersluice- gates without silt excluder, the value of C was related to H,/a, Reynolds number and the downstream slop . Comparison of this C value with that for horizontal floor showed that the effect bf downstream slope of the glacis is to increase the value of Cd. Application of energy and continuity equations yields a satisfactory discharge equation for flow through excluder. With excluder, the discharge through the excluder and gate opening has been expressed in terms of Q /(4, and H /a instead of any conventional discharge equatia. Here Q. is flow through the excluder and H is the head of water on the silt excluder measured from the-7 centre line of the excluder. The results also indicate that there is reduction in discharge through the sluice gate opening if excluder is also running simultaneously. Finally, the aspects which require collection of additional experimental data have been identified.