Particle's tracking in 3-D heterogeneous porous media transport models

The paper deals with the pathlines assessment in numerical 3-D models of groundwater. The correct pathlines definition is the prerequisite for catchment and pollutant arrival analyses for both the deterministic and stochastic approaches and its erroneous evaluation limits the validity of the numerical solutions. By the discretized models zero divergence or irrotationality (or both) are usually fulfilled in a week sense only and this fact is cause of errors in the particle's tracking procedures, principally when the media is dominated by the hydraulic conductivity spatial heterogeneity. To assess the accuracy of the 3-D pathlines the problem is here approached by the finite volume technique coupled with an improved Pollock post-processor that avoids the inconsistencies in singular points related to the week form of the velocity field solution. By this approach, consistent with the flues discretized field, it is possible to evaluate the pathlines in 3-D with a prescribed level of accuracy related to the domain discretization. Some tests define the convergence rate of the pathlines in heterogeneous media with increasing mesh refinement.