TITLE:
A New Space-Time CE/SE Numerical Tracking of Contaminant Transport in Fractured Stratified Geologic Profiles
AUTHORS:
Theophilus Akinfenwa Fashanu, Vincent Olusegun Sowemimo Olunloyo
KEYWORDS:
CE/SE Scheme; Contaminant Tracking; Freshwater Aquifer; Periodic Loading; Stratification
JOURNAL NAME:
Computational Water, Energy, and Environmental Engineering,
Vol.3 No.1,
December
11,
2013
ABSTRACT:
To date, efficient numerical simulation of contaminant transport in
geologic porous media is challenged by parametric jumps resulting from
stratification and the use of ideal initial/boundary conditions. Thus, to resolve
some contaminant hydrology problems, this work presents the development of the
Space-Time Conservation Element/Solution Element (CE/SE) scheme for advection-dispersion-reaction
a-d-r transport in geologic media. The CE/SE method derives from the native
form of Gauss conservation law. Therefore, it is able to effectively handle
non-trivial discontinuities that may exist within the problem domain. In
freshwater aquifer, stratification and other parametric jumps are examples of
such discontinuity. To simulate the Nigerian experience of nitrate pollution of
freshwater aquifers; the a-d-r contaminant transport model is herein solved
under a time periodic nitrate fertilizer loading condition on farmlands.
Results show that this approach is able to recover the well-known field pattern of nitrate profiles under
farmlands. Cyclic loading impacts more on the dispersivity of an aquifer. Hence,
dispersion coefficient modulates the response of aquifers to loading frequency.
However, aquifers with conductivity less than 10-6 m/day are almost insensitive to periodic loads.
The CE/SE method is able to sense slight (i.e.
order of 10-3) variation in hydrological parameters. Also, CE/SE
computes contaminant concentration and its flux simultaneously. Thus, it
facilitates a better understanding of some reported phenomena such as
contaminant accumulation and localized reverse transport at the interface
between fracture and matrix in geologic medium. Clearly, CE/SE is an efficient
and admissible tool into the family of numerical methods available for tracking
contaminant transport in porous media.