Turbulent flows in straight compound open-channel with a transverse embankment on the floodplain

24 The present study deals with turbulent flows in an asymmetrical compound channel with an 25 embankment set on the floodplain, perpendicularly to the longitudinal direction. The main purpose of 26 this study was to assess how a rapidly varied flow affects interaction between the floodplain flow and 27 the main channel flow. In addition to rapid changes in the water level and velocity across the 28 compound channel that have a great influence on the boundary shear stress distribution, the 29 embankment, through two recirculation zones developing upstream and downstream, is also 30 responsible for strong lateral mass exchange between the main channel and the floodplains (channel 31 sub-sections). The lateral velocity can indeed reach 50 % of the longitudinal velocity, which modifies 32 the characteristics of the mixing layer developing between the channel sub-sections. Depth-averaged 33 Reynolds shear stresses 5 times greater than those measured for reference flows are recorded within the 34 mixing layer, which indicates that the turbulent exchange is also impacted by the lateral mass 35 exchange. 36