A numerical model for calculation of advective-diffusive transport of
nonconservative substances in two-dimensional environments was developed. The
numerical method is based on the splitting-operator approach, in which the advection, the
diffusion and the chemicallbiological kinetic processes are calculated separately in one
time step. Special attention was paid to the advection operator, which introduces essential
difficulty in many numerical methods, and to the linearized source term which, in many
cases, has proven to cause instability problems. The model calculates pure advection by
the explicit Holly-Preissmann method of characteristics, and diffusion plus source/sink
terms by an extended implicit alternate-direction (ADI) method. By comparison with
analytical results for fronts and discrete mass releases it is established that numerical
separation of differential operators does not induce significant errors in the solution or the
physical realism of the results. The numerical scheme is accurate, stable and efficient
because it eliminates the need to solve a pentadiagonal algebraic systems, replacing it
with two tridiagonal ones. The computational method is intended for further use in the,
study of a two-dimensional lake hydrodynamic and transport field, driven either by
forced (wind induced) or natural (buoyancy induced) convection.
Office of Research and Development, US Environmental Protection Agency; Mid-Continent Ecology Division, US Environmental Protection Agency
Stefanovic, Dragoslav L.; Stefan, Heinz G..
Two-Dimensional Water Quality Model for Unsteady Advection-Diffusion of Nonconservative Substances.
St. Anthony Falls Laboratory.
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