Experimental study of transition and skimming flows on stepped spillways in RCC dams: qualitative analysis and pressure measurement

This paper is a presentation of an experimental facility used for analyzing the flow over the stepped spillway of an RCC dam. The technique of digitizing video sequences is applied in order to obtain a qualitative analysis of the hydraulic behavior of these chutes. The onset of skimming flow is studied using two different criteria: a visual criterion and another that makes use of the pressure pattern on the horizontal faces of the steps. The evolution along the length of the spillway of pressures measured on the centers of symmetry of the horizontal faces of the steps is also analyzed to obtain further conclusions regarding hydraulic behavior during a skimming flow regime.