Validation of a CFD model for flow in meandering rivers using an experimental test-setup: First results

A 3D Reynolds Averaged Navier Stokes (RANS) model of a meandering channel with rectangular cross-section has been developed using the commercial software package FLUENT 6.2. This model solves the 3D Navier-Stokes equations using the PISO scheme for the pressure-velocity coupling and the realizable k-?̊ model for turbulence closure. Output of the numerical model is compared to validation experiments conducted in a physical model, which represents two wavelengths of a regime channel and allows for the measurement of flow patterns at several discharges and variable bed forms. The computed water depths and velocity profiles of the CFD model output are in good agreement with the physical model results. The simulations slightly underpredict the streamwise velocities, which reach a maximum just before the apex of the meander bend, at the inner bank in the lower part of the flow depth. The CFD model also captures the motion of the secondary current or transverse flow well, showing the same direction of current along the entire second wavelength.