EXPERIMENTS ON STANDARD SPILLWAY FLOW

Two standard spillway geometries as typically encountered for high head dams are considered. The first corresponds to the Waterways Experiment Station profile, whereas the change of curvature for the second shape is continuous, and pressure conditions along the channel invert are slightly improved. The spillways considered are prismatic; they are high relative to the design head; and they do not have piers so that practically 2D flow conditions occur. The objective of this study is to establish the main flow features by experimental means. Normalized plots of two-dimensional velocity and pressure fields are presented, which are applicable to any scale. Further results include the minimum and the crest bottom pressures for which a linear relation with the relative head was found. Also, the coefficient of discharge is investigated. The present study includes two downstream chute slopes of 30-degrees and 45-degrees, and ratios of actual head to design head up to 4. The results are in agreement with previous studies, and may be used for the final design of high head spillways of which the head is beyond the design head.