DISCHARGE CHARACTERISTICS OF SLUICE GATES WITH DIFFERENT FLOOR CHARACTERISTICS

Abstract

Sluice gates are widely used for measuring, controlling and regulating the flows in hydraulic structures. Depending on the purpose and situation of flow condition these gates are provided at different locations. Sometimes, they are placed on a horizontal floor whereas in case of diversion strutures they are placed on a raised crest. However, a different situation arises when they are placed in the undersluice portion of barrages, in this case only the upstream floor is horizontal while the downstream floor is a sloping one and there is no .raised crest. The discharge characteristics of sluice gates kept on a horizontal floor and on a raised crest have been studied in the past whereas very limited information is available for undersluice gates. For sluice gates on a horizontal floor, the discharge characteristics have been studied by Henry [31, where as for sluice gates on a raised crest these characteristics have been studied by Ranga Raju and Visavadia [6] and Range Raju and Gopalkrishna [5]. Recently Sanjay (9] and Rekha Cal studied the discharge characteristics of undersluice gates with and without silt excluder. These studies have shown that the discharge characteristics of undersluice gates for such situations are quite different from those for sluice gates on horizontal floor and on a raised crest. Sanjay [93 and Rekha E8) proposed relationships for estimating the discharge through the undersluice gated flow without excluder. With excluder, relationships were also proposed for determining the discharges through and over the excluder using pertinent variables. The results of theses studies also indicated that with blockage in excluder, the gated discharge, over the for the case when flow is both through and over the excluder. However, all these results were on the basis of some simplified assumptions and on the basis of analysis of limited data.collected by them. The present experimental study has been take-up to examine the adequacy of various relationships proposed by Rekha C8] and to collect additional data to explore the possibility of modifying these relationships. Further, it was considered necessary to make detailed measurements concerning velocity distribution, pressure variation along the sloping glacis which were not measured in the previous studies. The present data were collected for a downstream sloping glacis of IN : 2.5H using two different heights of excluders i.e. 20mm and 50mm in a rectangular channel of width 0.6m and length 12.1m. In order to cover a complete range of slope for downstream glacis, data were collected for sluice gate located on a vertical drop.- Based *on the analysis of data collected in the present study as well as those collected by Sanjay E93 and Rekha [6], following discharge equation has been proposed for gated flow without excluder , q = a Cdi 2g HI where 'a' is the gate opening, H1 is the upstream head and Cd is given by, Ks Km Cd = 0.502 [H 1/a) 0.062 where in , K = 0.601 0.046 m R - and "K ' has been found to be a function of the slope of the downstream sloping glacis, Sd and is as shown in Fig. (4.24). For the case, when the flow is only through the excluder, without any flow over the excluder discharge equation proposed by Sanjay (9] (viii) was found to be satisfactory after considering friction losses. For the flow through and over the excluder, an approach has been suggested for estimating the excluder and gated flow discharge separately. Finally .for the gated flow over the excluder, considering excluder to be blocked following discharge eguation has been proposed. -- ej = 0.5 a a1 where Wo is the discharge per unit width over the excluder and He is the head above the excluder. Results based on measured velocity distribution, water surface and pressure variation along the sloping glacis of undersluice bays have also been presented in this dissertation.