International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395-0056
Volume: 11 Issue: 04 | Apr 2024
p-ISSN: 2395-0072
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Experimental Model Studies of Stilling Basin with Some Appurtenances H L Tiwari1, Kartikeya Mishra1, Bikram Prasad2 1Professor, Dept. of Civil Engineering, MANIT Bhopal, M.P., India
1Research Scholar, Dept. of Civil Engineering, MANIT Bhopal, M.P., India 2Associate Professor, Dept. of Civil Engineering, BIST Bhopal, M.P., India
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Abstract - This research paper describes experimental
jump-type stilling basins are the efficient mechanism for dissipating excess energy and the least prone to erosion and cavitation. This type of radiator has been widely used. The hydraulic jump is also assisted by the use of cross jets either from the surface or from the bed. The USBR stilling basins (Bradley and Peterka 1957), S.A.F. stilling basin. (Blaisdell 1948) and I.S. Stilling basins (2004) fall under this category. The designs are modified according to the prevalent site conditions (Mazumdar 2003). The S.A.F. stilling basins are shorter in length and they are mainly used on low head structures. An impact type of stilling basin is contained in a relatively small box type structure which does not have tail water requirements for proper performance. The USBR impact type VI stilling basin was mainly developed for the pipe outlets.
model studies on stilling basin which are performed to develop efficient and economical type stilling basin for non-circular pipe outlets for low Froud numbers. The experimental study was carried out for three Froude numbers, namely 3.85, 2.85 and 1.85 for the exit of the non-circular pipe. Performance of models were compared with non-dimensional parameters Performance criteria named as Performance Index (PI). Flow condition and running test hour was kept constant for all the tested model for particular Froud number. After analyzing eighteen tests, it was observed that the performance of the evolved stilling basin model also improved by reducing the basin length from 8.4d to 7d by introducing an intermediate sill of square section and new design of impact wall as comparison to USBRVI model. This model performed better than the USBR VI impact basin for similar flow conditions at a reduced length of 7d from 8.4d where d is the equivalent diameter of the pipe outlet with significant improved performance.
To reduce the high energy of flowing water, stilling basins are normally used (Tiwari et al. 2010). Dams and other hydraulic structures are planned to control large volumes of high pressure water (Sarma et al. 2009). The energies at the base of the structures are often enormous whether the discharge is through outlet conduits or over spillways. Some means of expending the energy of the high velocity flow are needed to prevent river bed runoff, minimize erosion, and prevent dam weakening. This can be achieved by constructing an energy dissipator at the base of the structure to dissipate excess energy from the water and establish safe flow conditions in the drainage channel (Pramanic and Mazumdar 1961). Any hydraulic energy dissipator's ability to function primarily lies on its ability to use one or combination of the techniques recommended by Govinda Rao (1961), Yang (1994), and Vischer and Hager (1995) to consume some of the energy of the high velocity flow. Stilling basins are an integral part of spillways, outlet works, diversion structures and waterfall structures (Tiwari 2013A).
Key Words: Pipe outlet, Stilling basin, Scour pattern, USBR
1.INTRODUCTION The water that comes out of an outlet in the tank, whether it be through gates, tunnels or pipes and over weirs, comes out at high speed, which is generated by varying its height potential drop from reservoir level to downstream river level (Mylvogonan and Rajaratnam 1961). This velocity is much higher than the natural safe velocity of stream at a given site, and causes scouring at the toe of the dam or other hydraulic structures. This scouring, if allowed to continue will undermine the foundation with consequent damage to the outlet structures, the outlet channel and sometimes the dam itself (Gehlot and Tiwari 2014). The hydraulic engineers are, therefore, facing with the problem of minimizing the energy of flowing water having high velocity for reducing the scour below the structure for a long time (Panwar and Tiwari 2014).
Various devices such as impact wall, intermediate and end sill etc. are used to make the stilling basin more efficient (Tiwari et al. 2014). The effect of the sill on the flow or scour characteristics depends on the configuration of the sill, its geometry and the flow regime, Negm (2004). Various types of stilling basin models recommended for pipeline releases are by Bradley and Peterka (1957), Fiala and Maurice (1961), Keim (1962), Vollmer and Khader (1971), Verma and Goel (2000 and 2003), Goel (2008), Tiwari et al. (2011, 2012, 2013, 2014 and 2015), Tiwari and Gahlot (2012), Tiwari (2013A and 2013B), Tiwari and Goel (2014
The hydraulic jump is an excellent tool for dissipating hydraulic energy, but it requires a greater length of the basin. The length of the hydraulic jump and therefore the length of the basin can be reduced by using devices in the form of baffle blocks, chute blocks, splitter blocks and end sill, etc. According to Murthy and Divatia (1982), hydraulic
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