25-08-2017, 09:32 PM
Abstracts: A hydraulic structure is required to be built on rivers, a sea or any body of water, where there is a need for a change in the natural flow of water. A hydraulic structure partially or completely obstructs the flow. Some examples of Hydraulic structures are Dam, Weir or Barrage. They raise the water level, and create the storage. The Stored water forms a manmade reservoir, which can be used for multiple purposes like irrigation, hydropower, flood protection, Navigation etc. Energy Dissipation Arrangement (EDA) is meant for downstream protection of hydraulic structure. When hydraulic structures like dam, weir or barrage etc. is constructed, it is essential to reduce the high velocity of the flow to some low velocity. This is essential to minimize the erosion of downstream bed of natural/ manmade channel. The reduction in velocity is achieved by any or a combination of the following: a) Hydraulic jump type stilling basins b) Jet diffusion and free jet stilling basins c) Bucket type dissipaters d) Intersecting jets and other special type of stilling basins The selection of the appropriate EDA depends upon the head, discharge intensity, tail-water conditions and the type of the bed rock or the bed material. In Hydraulic Jump type stilling Basin, the flow is required to be changed from supercritical to subcritical flow i.e. energy is dissipated by creation of hydraulic jump. Tail water conditions are very much important in deciding the type of energy dissipation arrangements. This phenomenon is utilized in hydraulic design of stilling basin. Stilling basins are external energy dissipaters placed at the outlet of a culvert, chute or falling jet of water. These basins are characterized by some combination of chute blocks, baffle blocks and sills designed to trigger a hydraulic jump in combination with a required tail water condition. The project focuses on the deciding of the most efficient type of energy dissipation arrangements for Garudeshwar weir which is now being constructed on River Narmada, downstream of Sardar Sarovar project for creation of tail pond for reversible operation of 200 MW x 6 Francis turbines (6 x 200 = 1200 MW). This project emphases on hydraulic design of stilling basin including physibility and geometrical design of various components like slope of the apron, end sills etc. to fulfill the function of energy dissipation at downstream of weir by methods prescribed in IS 4997-1968 (Reaffirmed 1995) and USBR using design parameters of overflow spillway block of Garudeshwar weir.