Computational method for three dimensional adcvection and dispersion in groundwater with horizontal zones and vertical layers

In this study an accurate and efficient three dimensional hybrid model has been developed. We need to consider both computational efficiency and the three dimensional characteristic for simulating the convective and dispersive transport in heterogeneous groundwater systems, while the present models are constructed with numerical scheme. Two dimensional models can’t present the three dimensional characteristic while the three dimensional ones are facing the computational difficulties caused by the difference between the length scale of horizontal direction and that of vertical direction. Thus, a new computational method is constructed.

In this study, the three dimensional advective-dispersive equation is decomposed into two-dimensional one (average of vertical integration) and one-dimensional one (vertical variation) by applying the assumption of quasi-three dimensional flow concept and the application of vertical integration technique. The two dimensional horizontal advection- dispersion equation is computed by the finite analytic method which is unconditional stable and is capable of accurately computing the advective-dispersive phenomena. On the other hand, the one-dimensional vertical part is solved analytically. We also add horizontal zones and vertical layers technique for modeling the advective-dispersive phenomena in heterogeneous layered groundwater systems.

The computational results are verified with analytical solutions and in situ field experiments. The results show that the proposed model can indeed simulate the contaminant transport in the groundwater accurately and efficiently.