Computer prediction of subsurface radionuclide transport: an adaptive numerical method
Radionuclide transport in the subsurface is often modeled with the aid of the advection-dispersion equation. A review of existing computer methods for the solution of this equation shows that there is need for improvement. To answer this need, a new adaptive numerical method is proposed based on an Eulerian-Lagrangian formulation. The method is based on a decomposition of the concentration field into two parts, one advective and one dispersive, in a rigorous manner that does not leave room for ambiguity. The advective component of steep concentration fronts is tracked forward with the aid of moving particles clustered around each front. Away from such fronts the advection problem is handled by an efficient modified method of characteristics called single-step reverse particle tracking. When a front dissipates with time, its forward tracking stops automatically and the corresponding cloud of particles is eliminated. The dispersion problem is solved by an unconventional Lagrangian finite element formulation on a fixed grid which involves only symmetric and diagonal matrices. Preliminary tests against analytical solutions of ne- and two-dimensional dispersion in a uniform steady state velocity field suggest that the proposed adaptive method can handle the entire range of Peclet numbers from 0 to infinity, with Courant numbers well in excess of 1.
- Research Organization:
- Arizona Univ., Tucson (USA). Dept. of Hydrology and Water Resources
- OSTI ID:
- 6493395
- Report Number(s):
- NUREG/CR-3076; ON: DE83901349
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
Aquatic-- Radioactive Materials Monitoring & Transport-- Water-- (1987)
54 ENVIRONMENTAL SCIENCES
ADVECTION
COMPUTERIZED SIMULATION
DIFFUSION
ENVIRONMENTAL TRANSPORT
FINITE ELEMENT METHOD
FUNCTIONS
GROUND WATER
HYDROGEN COMPOUNDS
LAGRANGIAN FUNCTION
MASS TRANSFER
MATHEMATICAL MODELS
NUMERICAL SOLUTION
OXYGEN COMPOUNDS
RADIONUCLIDE MIGRATION
SIMULATION
WATER