Department of Civil Engineering, Indian Institute of Technology, Roorkee
The most common type of weir adopted in boulder streams for diversion of water for hydropower generation, water supply, irrigation etc. is the trench weir. It consists of a transverse trench in the streambed covered with metal bottom rack to prevent the transport of unwanted solid material into the trench. Most of the studies on the characteristics of flow over bottom racks are limited to bottom racks made of circular bars. However, from structural consideration, flat bars are preferred to circular bars as the flat bars have more flexural rigidity. The present paper deals with characteristics of flow over bottom racks made of flat bars. Experiments were performed to collect the relevant data. Variation of specific energy over the rack is constant. Existing relationship for coefficient of discharge is not accurate and thus a new relationship is proposed in this study, which estimates the value of coefficient of discharge within ±10% error.
Bottom racks, Flat bars, Trench weir, Hilly streams, Hydropower
