The Bhakra Dam is provided with two tiers of river outlets located at elevations 1420 and 1320. It was apprehended that the working of the outlets in the two tiers might result in their mutual interference which may be in both horizontal and vertical directions. Furthermore, in the event of escapage of flood discharges over the spillway crest, it was probable that the high velocity jet of overflow might press down the jets emerging from the river outlets and thus affect the flow pattern within the conduits of the river outlets. For reducing the effect of the flow over the crest on the flow through the river outlets, the outlet channels on the spillway face have been provided with eye-brows. But it was felt that the maximum thickness of the eye-brows being only 2 ft. (0.6 m.) at their downstream ends, they would not effectively shield the flow through the river outlets. This effect could result in change in the pressure distribution within the conduits and their discharging capacity. Studies were, therefore, made on different scale models to determine the discharge through the two tiers of outlets when opened singly as well as in combination and also with maximum flood discharge of 1,90,000 cusec passing over the spillway.
The studies indicated that while there was a very little mutual interference of the outlets in the two tiers either in horizontal or vertical directions, the flow over the spillway caused a small reduction of about 2.6 per cent in the combined discharge through all the river outlets.
These are very important results which are of application to flow through the outlets on dams in general.
