Study on Designing New Stilling Basin Model for Dam Pipe Outlet

Abstract

Dams are the big structures which contains large amount of water. When this stored water is released for irrigation, or any other purpose, flowing water acquired high flow energy which may endanger the dam or downstream structures. To safeguard such disastrous failure Stilling basins are constructed to reduce the excess energy, contained by high velocity flow, on the downstream face of the outlet of the conduit, so that the flow beyond the basin does not endanger the stability of bed and banks of the downstream channel. An experimental investigation, leading to the development of a new stilling basin design with different appurtenances, is reported in this article. On the basis of an experimental work, the USBR VI stilling basin model was modified to make the new stilling basin model more effective and economical. Three modifications, resulting in three new models, were tested for Froude numbers as Fr = 1.85, 2.85 & 3.85 and were compared with the USBR VI stilling basin model recommended for pipe outlets. The new models were studied by putting inverted T shaped splitter block, while keeping the other configuration of stilling basin geometry the same as suggested by USBR VI stilling basin. The performance of the basin was evaluated using a performance index (PI). After twelve test runs, it was found that for a given Froude number range, the insertion of the splitter block keeping the same impact wall along with the end sill improved the performance of stilling basin and the length of the newly studied basin reduced by 29% as compared to the USBR VI stilling basin for given flow conditions.