Author(s): Sibel Kara; Thorsten Stoesser; Terry W. Sturm
Keywords: Apparent shear stress; compound open channel flow; large eddy simulation; streamwise momentum balance; turbulence-driven secondary flow
Abstract: The results of large eddy simulations (LESs) of turbulent flow in a compound open channel with deep and shallow flood plain depths are presented. These LESs are validated with experimental data, resulting in a good agreement between measured and calculated data. The floodplain-depth-to-main-channel-depth ratio is an important parameter affecting first- and second-order turbulence statistics. The streamwise momentum balance is analysed with respect to the momentum transfer at the interface between the main channel and the floodplain. Depth-averaging of the streamwise momentum equation reveals the dominance of turbulent shear stress terms in the main channel and of secondary currents in the floodplain. Comparisons of the LES results with an analytical solution of the depth-averaged streamwise momentum equation that demonstrate the importance of case-specific calibration of the parameters of the analytical solution. The turbulence anisotropy is quantified and its role in generating secondary currents is illustrated.