Investigation the Effect of Longitudinal Profile of Stepped Spillway on Flow Energy Dissipation

In a stepped spillway, the steps can considerably reduce the flow energy. The purpose of this study was to investigate and comparing the amounts of energy dissipation in stepped spillways with different longitudinal profiles using physical models. For this purpose the experiments were done in a channel with 12 meters of length, 0.5 meter of width and 0.8 meter of height. For doing this research, the stepped spillways that had plexi glass gender with 4 ratios of hL = 0.5, 0.67, 1 and 2 was designed and constructed. The results showed that the amount of energy dissipation in hL=1 have maximum value, in the other words, when step length and step height be equal causes energy dissipation will be more. The results showed for hL≤1, increasing height of steps has been increase the energy dissipation. In a constant ych, the increase in the number of steps Increases relative energy dissipation and increasing dimensionless parameter ych, reduces energy dissipation almost 5 %. Finally, third degree equations for relative energy dissipation extracted, that the calculated statistical parameters indicate high accuracy of equivalents. The results showed relative energy dissipation in our study was in agreement with Chanson equations and Fratino-Piccinni equations.