Momentum dispersion and wall friction in free surface flows above non-uniform bottom roughness

The effects of secondary flows on the momentum dispersion were analyzed in this study, for the case of free surface flows above non-uniform bottom roughness. In a first step, 3D-simulations were achieved using an anisotropic Reynolds stress model to determine the wall friction and the dispersion terms present in the depth averaged momentum equation. In a second step closure assumption of these terms were tested to define a 2D-Saint Venant model which is solved to calculate the transverse profile of the depth-averaged velocity. This approach was applied, to experiments achieved in a free surface flows above non-homogeneous rough bottom in a rectangular channel (realized at the 'Institut de Mecanique des Fluides de Toulouse -IMFT-'), and also to experimental results available in literature, and witch are achieved in open channels with periodic transverse variation of the bottom roughness.