Free-surface Profiles and Turbulence Characteristics in Skimming Flows along Stepped Chutes

The behavior of the free surface in skimming flows along stepped chutes is investigated for the step ratio 1V:1H. Data were collected using high frequency ultrasound probes. The measurements included mean surface profiles, statistical parameters related to the surface position, aeration inception point, water depth at the inception point and transition length. The measurements were related to turbulence parameters at the free surface. The measurement methodology was adequate for both the black-water and the white-water regions. Characteristic relations are developed for different variables defined for skimming flows. The results demonstrate regions of increasing and decreasing turbulence in the transition between the black-water and the white-water flows, and a region of decay of turbulence, related to the distance needed to attain the quasi-uniform flow of the white-water.