S.A Sadrnejad - Professor, Civil Engineering Department, K.N.Toosi University of Technology, Tehran, Iran
S.A Ghoreishian Amiri - PhD student, Civil Engineering Department, K.N.Toosi University of Technology, Tehran, Iran

Numerical solutions are widely used as screening tools for estimating the potential of contaminant transport in groundwater. Finite element with Galerkin method is common for numerical solution of these problems. However advection, diffusion terms and their interactions in the differential equation of contaminant transport caused some oscillations in the results produced by this method. In this paper, advection- diffusion- first order reaction equation has been considered. Classical Galerkin finite element method has been used for discretization of the equation in spatial domain and finite difference method has been employed for discretization in time domain. There is some oscillation in the result of this method at the point where the solute doesn’t reach. So we have developed a numerical technique by using an artificial boundary conditioning for sorting out these oscillations. In fact we have made a smaller domain in each step by indentifying the domain of solute propagation. The result of the method has been compared with analytical solution of the equation and reasonable agreement has been achieved.

Contaminant transport, Finite element method, Galerkin method, Numerical oscillation, Artificial boundary condition