Aerated flows on stepped chutes with macro-roughness elements, Part II : Energy dissipation

An experimental research of flow on different systems of stepped overlays for 18.6 degrees and 30 degrees slopes was conducted. In addition to define flow characteristics (Part I), the study highlighted the existence of an homogeneous aerated flow in which drag effect caused by the macro-roughness contribute significantly in the energy dissipation process. The analysis of the different flow depths and of several macro-roughness systems lead to an accurate method for estimation of residual energy of the aerated turbulent flow. Finally, based on the hydraulic behaviour of aerated turbulent flow and on the measured pressures on macro-roughness elements as well as on the energy dissipation efficiency of the tested systems, recommendations for the design of an optimal protection overlay for overtopped embankment dams are given.