Author(s): Didier Bousmar; Yves Zech
Linked Author(s): Yves Zech, Didier Bousmar, K.L. Meijer
Keywords: Compound channels; Floodplains; Turbulence structures; Vortex; Shear layer; Large eddy simulation; Depth-averaged; Numericalmodelling
Abstract: This paper presents a theoretical and numerical study of the periodicity of the large vortices with vertical axis, located at the shear layers between the main channel and the floodplains of a flooded river. Those vortices are known to be responsible for a large momentum transfer and a subsequent conveyance reduction in compound channels. It is expected that a better knowledge of their structure could help in evaluating their effect on the channel conveyance. A hydrodynamic stability analysis of a parallel shear flow gives preliminary results on the vortices periodicity. The interaction between the two shear layers existing in a compound channel with two floodplains is briefly commented. The vortices generation is then modelled using a depth-averaged Large Eddy Simulation model. In those simulation, due to instabilities, the shear layers break up into separate vortices, whose spatial periodicity is found close to data previously published by Sellin. The vortex influence on the velocity profile and on the transversal shear stress distribution is also discussed.