International Journal of Thermal and Fluid Sciences2225-3556xxxx-xxxxAsian Network for Scientific Information10.3923/ijtfs.2012.1.10PirestaniM.R.RazmkhahA.GhobadiF.1201211Energy dissipaters are usually used for release of energy at the downstream outlet of the spillway. Stilling basins are the most important type of these structures. Baffle piers and sills are used in implicit basins for decreasing hydraulic jump length and economic costs. Researches illustrated that the effect of mentioned components on decreasing of hydraulic jump length depend on basin dimensions, height and location of blocks and spacing between them. In this research the effect of geometric-hydraulic parameters on energy dissipation and hydraulic jump location have been experimented by change in baffle piers and end sill structures and convergence of walls in different discharges. To reach this goal, physical model of Nazloochay dam with 1:40 scale was constructed. Experiments were done in different cases: separate blocks with different dimensions, the effect of stepped surface instead of end sill and convergence of walls at the end of basin in 5, 7.5,10, 12.5 degrees. With discharge variation in control section of river in each experiment, the values of depth, velocity and static pressure in basin were measured. According to results application of these steps instead of end sill blocks at the end of stilling basin was not successful on stabilize the hydraulic jump in the basin specially in large discharges. But in the case of converged walls in all experimented degrees, submerged hydraulic jump formed. Convergence also has positive effect on energy dissipation and efficiency of hydraulic jump, 5 degree of convergence has the best operation.]]>Arbhabhirama, A. and A.U. Albella,1971Esmaeeli varaki, M.,2003Ezizah, G., N. Yousif and S. Mostafa,2012Izadjoo, F. and M. Shafai-Bejestan,2007Omid, M.H.,1996Rizi, A.P., S. Kouchakzadeh and M.H. Omid,2006Peterka, A.J.,1983Posey, C.J. and P.S. Hsing,1938Bejestan, M.S. and K. Neisi,2009Wanoschek, R. and W. Hager,1989