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An investigation of numerical grid effects in parameter estimation
George A Zyvoloski1, Velimir V Vesselinov
1Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA. gaz@lanl.gov
Ground Water
|November 8, 2006
Summary
Numerical model accuracy in groundwater studies is crucial. Conformable grids offer accurate solutions for complex hydrogeology, while the control volume finite-element method improves parameter estimation over finite-difference methods.
Area of Science:
- Hydrogeology
- Numerical modeling
- Computational hydraulics
Background:
- Groundwater characterization and remediation demand calibrated numerical models of complex hydrogeological systems.
- Hydrogeologic complexity arises from factors like spatial hydrostratigraphy and unsaturated zone infiltration.
- Computational efficiency often necessitates compromises in model grid resolution and numerical flow equation representation.
Purpose of the Study:
- To investigate the impact of grid properties, resolution, and computational schemes on numerical model predictions and inverse parameter estimates.
- To evaluate the effectiveness of "conformable" grids in handling complex hydrostratigraphy.
- To compare the accuracy of the control volume finite-element method (CVFEM) against finite-difference (FD) techniques for parameter estimation.
Main Methods:
- Analysis of one- and two-dimensional synthetic cases.
- Simulation of saturated and variably saturated flow problems.
- Comparison of "conformable" grids and standard numerical schemes.
- Evaluation of CVFEM and FD methods for parameter estimation.
Main Results:
- "Conformable" grids can yield accurate solutions for complex hydrostratigraphy, even with numerical formulation simplifications.
- The control volume finite-element method demonstrated superior accuracy in parameter estimation compared to finite-difference techniques for a given grid resolution.
- CVFEM exhibited slower run times and higher memory demands, but provided more reliable parameter estimates.
Conclusions:
- Careful consideration of grid properties and computational schemes is essential for reliable groundwater model calibration and analysis.
- "Conformable" grids represent a viable approach for modeling complex hydrogeological systems efficiently and accurately.
- The control volume finite-element method is recommended for groundwater parameter estimation when accuracy is paramount, despite increased computational costs.
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