Saturation of curvature-induced secondary currents in relatively sharp bends: A two-dimensional modelling approach

Secondary currents occurring in channel bends have manifold implications in river hydraulics. In reduced-order models, the typical parametrizations of helical flow assume their magnitude to increase linearly with the channel curvature, although this is valid only in mild-curvature bends. In sharper ones, the non-linear interaction between the primary and the secondary flow flattens the vertical profile of longitudinal velocity component, thus reducing the source mechanism of the secondary current. Established models for this so-called "saturation effect" all refer to the channel centreline. In this work, a pure 2D implementation of a saturation model is included in a Finite Element depth-averaged hydrodynamic model based on a Cartesian reference frame.