Transition length between water and air-water flows on stepped chutes

This study presents the steps followed to obtain mathematical models for the length of the transition region between the “full-water” and “full-mixed” flows in stepped spillways. This transition length is defined here as the distance along the flow, parallel to the pseudo-bottom, starting at the end of the “full-water” region and ending at the beginning of the “full-mixed” region. The definition is proposed based on experimental profiles of the surface obtained with an acoustic sensor in a stepped chute, which allows one to locate adequately the minima and maxima of the profile. A set of profiles obtained for different flow conditions is shown, and a comparison between predicted and calculated transition lengths is made. Experimental data and theoretical predictions superpose adequately for the present set of data.