Development of physically based meshes for two-dimensional models of meandering channel flow

The choice of mesh generation and numerical solution strategies for two-dimensional "nite element models of #uvial #ow have previously been based chie#y on experience and rule of thumb. This paper develops a rationale for the "nite element modelling of #ow in river channels, based on a study of #ow around an annular reach. Analytical solutions of the two-dimensional Shallow Water (St. Venant) equations are developed in plane polar co-ordinates, and a comparison with results obtained from the TELEMAC-2-D "nite element model indicates that of the two numerical schemes for the advection terms tested, a #ux conservative transport scheme gives better results than a streamline upwind Petrov}Galerkin technique. In terms of mesh discretization, the element angular deviation is found to be the most signi"cant control on the accuracy of the "nite element solutions. A structured channel mesh generator is therefore developed which takes local channel curvature into account in the meshing process. Results indicate that simulations using curvature-dependent meshes o!er similar levels of accuracy to "ner meshes made up of elements of uniform length, with the added advantage of improved model mass conservation in regions of high channel curvature