A ROBUST AND EFFICIENT NUMERICAL-MODEL FOR ANALYSES OF DENSITY-DEPENDENT FLOW IN POROUS-MEDIA

A new computer code (MITSU3D) has been developed to simulate variable density-dependent flow in porous media. The techniques involve a contr ol-volume discretization, Newton-Raphson linearization, and a flux lim iter scheme. The assembled Jacobian matrices are solved by using preco nditioned conjugate gradient-type methods employing a block-incomplete LU factorization and reduced system preconditioning. Numerical simula tions involving contaminant migration in a two-dimensional cross-secti on show MITSU3D to be much faster and more robust than SUTRA. MITSU3D successfully avoids an ''error-driven'' contaminant plume instability in a coarse grid discretization and shows increased performance by a f actor of five. The enhanced speed and robustness will enable us to exa mine much larger coupled problems than heretofore had been considered computationally practical. (C) 1998 Elsevier Science B.V. All rights r eserved.