Uniform Aerated Chute Flow

Uniform flow with natural air entrainment on spillway chutes is considered. Based on the experimental data of Straub and Anderson, the air-concentration profiles are first investigated. A similarity plot is presented, which unifies the data pertaining to various chute slopes. First, an expression for the average air concentration is deduced. The latter increases almost linearly with the chute slope. Second, the ratio between the air-water mixture flow depth and the pure water depth is analyzed. Based on previous findings, a simple formula is deduced for wide chutes. According to this relation, the bulkage of uniform aerated flow depends mainly on the chute slope, moderately on the roughness coefficient and only insignificantly on the uniform flow depth. These findings may then be brought in relation to those previously established and pertaining to the average air concentration.