Numerical Simulation of the Convective Transport of a Noninteractive Chemical Through an Unsaturated/Saturated Porous Media

Abstract

ABSTRACT Aparticle tracking model is developed to determine location, pathway, and arrival time of a noninteractive chemical as it migrates through a heterogeneous, anisotropic, saturated/unsaturated transient porous media. The model is capable of accurately simulating particle movement through a wide variety of subsurface configurations at relatively low computer costs. The computation speed allows for the selection of small time steps and the solution scheme can solve for a velocity vector at any location within the subsurface regime. This combination improves on the prediction of particle pathways by describing flow throughout the entire media, rather than depending on average values of flow velocity. Input for the model is the initial location of the chemical particle, moisture characteristic and hydraulic conductivity functions of each soil, and the total potential distribution. The velocity vector at the particle's exact internodal position is determined by a series of one-dimensional numerical solution schemes. The particle is then moved as a function of the interpolated velocity vector and the time step length. The accuracy of the model is tested by comparing the simulated results to analytical solutions of three subsurface flow problems. Examples of particle tracking through three hypothetical flow systems are presented to illustrate the usefulness and flexibility of the model....