Secondary flow and bed slope effects contributing to ill-posedness in river modelling

Abstract

Two-dimensional fl ow models are widely used and necessary to predict phenomena such as the dynamics of bars. In these problems the effect of the bed slope in the direction of the sediment transport rate needs to be accounted for to obtain physically realistic results. This effect is included using an empirical closure relation. Even including bed slope effects, 2D models do not capture 3D phenomena such as secondary fl ow which occurs when the fl ow curvature
is large. This process is accounted for in a parameterized manner including one equation to model the advection and diffusion of the secondary fl ow intensity.