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

The choice of mesh generation and numerical solution strategies for two-dim ensional finite element models of fluvial flow have previously been based c hiefly on experience and rule of thumb. This paper develops a rationale for the finite element modelling of flow in river channels, based on a study o f flow around an annular reach. Analytical solutions of the two-dimensional Shallow Water (St. Venant) equations are developed in plane polar co-ordin ates, and a comparison with results obtained from the TELEMAC-2-D finite el ement model indicates that of the two numerical schemes for the advection t erms tested, a dux conservative transport scheme gives better results than a streamline upwind Petrov-Galerkin technique. In terms of mesh discretizat ion, the element angular deviation is found to be the most significant cont rol on the accuracy of the finite element solutions. A structured channel m esh generator is therefore developed which takes local channel curvature in to account in the meshing process. Results indicate that simulations using curvature-dependent meshes offer similar levels of accuracy to finer meshes made up of elements of uniform length, with the added advantage of improve d model mass conservation in regions of high channel curvature. Copyright ( C) 2000 John Wiley & Sons, Ltd.