WEIGHTED IMPLICIT FINITE-VOLUME MODEL FOR OVERLAND-FLOW

A weighted implicit finite-volume model is developed to simulate two-d imensional diffusion how in arbitrarily shaped areas. The model uses a mixture of unstructured triangles and quadrilaterals to discretize th e domain, and a mixture of cell wall types to describe structures, lev ees, and flow functions that characterize two-dimensional flow. The im plicit formulation makes the model stable and run faster with very lar ge time steps. The sparse system of linear equations that results from the implicit formulation is solved by using iterative solvers based o n various preconditioned conjugate gradient methods. The model was tes ted under a variety of conditions. The results were compared with resu lts from known models applied to axisymmetric and other test problems that had known solutions. The model was applied successfully to the ox bow section of the Kissimmee River in Florida, and the results were co mpared with results from physical and numerical modeling studies. This analysis indicated that the circumcenter-based flow function for wall s that is used in the model gives overall superior results in all the cases considered. Results of the numerical experiments showed that the use of weighted implicit methods and iterative solvers provide modele rs with improved flexibility and control of the overall accuracy and t he run time. The method is to be used as the solution method for the S outh Florida Regional Simulation Model.