Scale Effect of the Water Surface Profile on Ogee Spillway with Curvature in Plan and Converging Training Walls

The water surface profiles on spillway are important for design of free board and spillway training wall height. The engineers have used physical modeling to design these kinds of structures, Considering that the scale effect in the spillway modeling, leads to the different measured data between model and prototype, in this study, an experimental model based on Garmi-Chay Mianeh dam spillway was designed in three 1:100, 1:75, and 1:50 scales. Next, the water surface profile on spillway crest measured in seven discharges and compared with basic scale of (1:50), the percentage of water level difference on the crest calculated in two physical models with 1:100 and 1:75 scales. Results and observations revealed that in due to the effect of viscosity and surface tension the difference of water level in the scale of 1:100 and 1:75 was 18.4% and 15.6% respectively, relative to the base scale. The larger discharge, water level on spillway increases, leads to decrease viscosity and surface tension effects. For the difference in water level in the scale of 1:100 and 1:75 was 5.8% and 4.8% respectively relative to the base scale. In this study, viscosity and surface tension effects is stated with correction equation (K'), that was functions of Reynolds and Weber numbers. With the ogee spillway modeling the effect of viscosity in Reynolds numbers larger than 3.1*104 and the effect of tension surface in Weber numbers larger than 270 can be neglected and by extrapolation prototype results from model studies can be obtained.