10.4122/1.1000000293
Pereira, Felipe
Felipe
Pereira
felipe-pereira@uol.com.br
Aquino, José
José
Aquino
jaquino@iprj.uerj.br
Francisco, Alexandre
Alexandre
Francisco
afrancisco@iprj.uerj.br
Amaral Souto, Hélio
Hélio
Amaral Souto
helio@iprj.uerj.br
Pereira, Felipe
Felipe
Pereira
felipe-pereira@uol.com.br
Contaminant Transport in Unsaturated Heterogeneous Formations
XVI International Conference on Computational Methods in Water Resources
2006
2006
Leaking nuclear waste repositories in unsaturated soils can be of significant impact
to the environment due to transient water infiltration. In order to investigate this
problem
through numerical simulations we have developed a simulator which takes into account the
interaction of radionuclide plumes and two-phase (air-water) flows.
We introduce an operator splitting scheme which allows us to solve the governing
equations
with appropriate numerical methods. For the advective transport of solute plumes we
employ eulerian-lagrangian techniques. We approximate the two-phase flow problem
combining
a conservative, second order, non-oscillatory central scheme [1] for saturation
transport with
mixed finite elements for both diffusion and velocity calculations [2].
Numerical simulations in heterogeneous porous media are presented. For the approximation
of the advective transport of solute plumes we compare the Modified Method of
Characteristics
(MMOC) [3], the Locally Conservative Eulerian-Lagrangian Method (LCELM) [4], and a new,
locally conservative lagrangian procedure developed by the authors. Our numerical
experiments
indicate that the new procedure produces more accurate predictions than the other
methods;
moreover, it is virtually free of numerical diffusion.
References:
[1] N. Nessyahu and E. Tadmor, Non-Oscillatory Central Differencing for Hyperbolic
Conservation Laws,
J. Comput. Phys., 87, vol. 2, pp. 408-463, 1990.
[2] J. Douglas, Jr. and F. Furtado and F. Pereira, On the numerical simulation of
waterflooding of
heterogeneous petroleum reservoirs. Comput. Geosc., 1, pp. 155-190, 1997.
[3] J. Douglas, Jr. and T. Rusell, Numerical methods for convection-dominated
diffusion problems
based on combining the method of characteristics with finite element or finite difference
procedures, SIAM J. Num. Anal., vol.19, pp. 871-885, 1982.
[4] J. Douglas, Jr., F. Pereira, and L. M. Yeh, A locally conservative
Eulerian-Lagrangian
numerical method and its application to nonlinear transport in porous media. Comput.
Geosc., 4 , pp. 1-40, 2000.