This thesis investigates compound-channel flows, featuring an asymmetric arrangement consisting of a main channel and one floodplain. Such channels, prevalent in urban and natural environments, present challenges in understanding their unique geometry-induced flow behaviors. The study focuses on the interaction between the main channel and floodplain, examining turbulent anisotropy, longitudinal secondary currents, the development of the shear layer in the junction region, and the formation of interface vortices. The research evaluates the limitations of existing descriptors, specifically the depth ratio D_r and shear parameter łambda, in characterizing compound-channel flows. Employing wall-resolved large-eddy simulation with the MGLET solver and the WALE sub-grid model, the simulation successfully captures the overall flow behavior, showing good agreement to experimental data. The investigation of the junction region and developed shear layer reveals that Reynolds stresses dominate momentum transfer toward the junction region in the main channel, while lateral advection prevails in the floodplain. The junction region exhibits high peaks of stresses and turbulent kinetic energy, with the shear layer manifesting as a constant band, intriguingly offset from the junction-region center-line but in the main channel region. The proposed flow classification based on the depth ratio D_r is found less valuable. Despite criticisms of the shear parameter łambda for neglecting shear-layer width and including primary convection, the threshold holds true for the given case, as no Kelvin-Helmholtz coherent structures are identified. However, the instantaneous pressure field reveals 2D vortical structures near the shear-layer center-line, and spontaneously occurring small-scale vortices with vertical axes are discovered at the free surface using the Q-criterion, mainly near the walls and in the junction and floodplain regions. Despite observing a 2D macro vortex, the absence of a developed Kelvin-Helmholtz coherent structures streak emphasizes the complexity of compound-channel flows. The identified disparities underscore the need for careful investigation, indicating a lack of methodologies for predicting shear layer behavior and Kelvin-Helmholtz coherent structures development in compound-channel flows.     «

This thesis investigates compound-channel flows, featuring an asymmetric arrangement consisting of a main channel and one floodplain. Such channels, prevalent in urban and natural environments, present challenges in understanding their unique geometry-induced flow behaviors. The study focuses on the interaction between the main channel and floodplain, examining turbulent anisotropy, longitudinal secondary currents, the development of the shear layer in the junction region, and the formation of i...     »