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Title: NEW GHOST-NODE METHOD FOR LINKING DIFFERENT MODELS WITH VARIED GRID REFINEMENT

Abstract

A flexible, robust method for linking grids of locally refined models constructed with different numerical methods is needed to address a variety of hydrologic problems. This work outlines and tests a new ghost-node model-linking method for a refined ''child'' model that is contained within a larger and coarser ''parent'' model that is based on the iterative method of Mehl and Hill (2002, 2004). The method is applicable to steady-state solutions for ground-water flow. Tests are presented for a homogeneous two-dimensional system that has either matching grids (parent cells border an integer number of child cells; Figure 2a) or non-matching grids (parent cells border a non-integer number of child cells; Figure 2b). The coupled grids are simulated using the finite-difference and finite-element models MODFLOW and FEHM, respectively. The simulations require no alteration of the MODFLOW or FEHM models and are executed using a batch file on Windows operating systems. Results indicate that when the grids are matched spatially so that nodes and child cell boundaries are aligned, the new coupling technique has error nearly equal to that when coupling two MODFLOW models (Mehl and Hill, 2002). When the grids are non-matching, model accuracy is slightly increased over matching-grid cases. Overall, resultsmore » indicate that the ghost-node technique is a viable means to accurately couple distinct models because the overall error is less than if only the regional model was used to simulate flow in the child model's domain.« less

Authors:
; ; ; ; ; ;
Publication Date:
Research Org.:
Yucca Mountain Project, Las Vegas, Nevada
Sponsoring Org.:
USDOE
OSTI Identifier:
884895
Report Number(s):
NA
MOL.20060403.0191, DC#46977; TRN: US200616%%148
DOE Contract Number:
NA
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; 99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE; HYDROLOGY; GROUND WATER; ITERATIVE METHODS; FLOW MODELS; M CODES; F CODES; COUPLING

Citation Formats

S.C. James, J.E. Dickinson, S.W. Mehl, M.C. Hill, S.A. Leake, G.A. zyvoloski, and A. Eddebbarh. NEW GHOST-NODE METHOD FOR LINKING DIFFERENT MODELS WITH VARIED GRID REFINEMENT. United States: N. p., 2006. Web. doi:10.2172/884895.
S.C. James, J.E. Dickinson, S.W. Mehl, M.C. Hill, S.A. Leake, G.A. zyvoloski, & A. Eddebbarh. NEW GHOST-NODE METHOD FOR LINKING DIFFERENT MODELS WITH VARIED GRID REFINEMENT. United States. doi:10.2172/884895.
S.C. James, J.E. Dickinson, S.W. Mehl, M.C. Hill, S.A. Leake, G.A. zyvoloski, and A. Eddebbarh. Wed . "NEW GHOST-NODE METHOD FOR LINKING DIFFERENT MODELS WITH VARIED GRID REFINEMENT". United States. doi:10.2172/884895. https://www.osti.gov/servlets/purl/884895.
@article{osti_884895,
title = {NEW GHOST-NODE METHOD FOR LINKING DIFFERENT MODELS WITH VARIED GRID REFINEMENT},
author = {S.C. James and J.E. Dickinson and S.W. Mehl and M.C. Hill and S.A. Leake and G.A. zyvoloski and A. Eddebbarh},
abstractNote = {A flexible, robust method for linking grids of locally refined models constructed with different numerical methods is needed to address a variety of hydrologic problems. This work outlines and tests a new ghost-node model-linking method for a refined ''child'' model that is contained within a larger and coarser ''parent'' model that is based on the iterative method of Mehl and Hill (2002, 2004). The method is applicable to steady-state solutions for ground-water flow. Tests are presented for a homogeneous two-dimensional system that has either matching grids (parent cells border an integer number of child cells; Figure 2a) or non-matching grids (parent cells border a non-integer number of child cells; Figure 2b). The coupled grids are simulated using the finite-difference and finite-element models MODFLOW and FEHM, respectively. The simulations require no alteration of the MODFLOW or FEHM models and are executed using a batch file on Windows operating systems. Results indicate that when the grids are matched spatially so that nodes and child cell boundaries are aligned, the new coupling technique has error nearly equal to that when coupling two MODFLOW models (Mehl and Hill, 2002). When the grids are non-matching, model accuracy is slightly increased over matching-grid cases. Overall, results indicate that the ghost-node technique is a viable means to accurately couple distinct models because the overall error is less than if only the regional model was used to simulate flow in the child model's domain.},
doi = {10.2172/884895},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Feb 15 00:00:00 EST 2006},
month = {Wed Feb 15 00:00:00 EST 2006}
}

Technical Report:

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  • A flexible, robust method for linking grids of locally refined models that may be constructed using different types of numerical methods is needed to address a variety of hydrologic problems. This work outlines and tests a new ghost-node model-linking method based on the iterative method of Mehl and Hill (2002, 2004). It is applicable to steady-state solutions for ground-water flow. Tests are presented for a homogeneous two-dimensional system that facilitates clear analysis of typical problems. The coupled grids are simulated using the finite-difference and finite-element models MODFLOW and FEHM. Results indicate that when the grids are matched spatially so thatmore » nodes and control volume boundaries are aligned, the new coupling technique has approximately twice the error as coupling using two MODFLOW models. When the grids are non-matching; model accuracy is slightly increased over matching grid cases. Overall, results indicate that the ghost-node technique is a viable means to accurately couple distinct models.« less
  • A flexible, robust method for linking grids of locally refined models constructed with different numerical methods is needed to address a variety of hydrologic problems. This work outlines and tests a new ghost-node model-linking method for a refined 'child' model that is contained within a larger and coarser 'parent' model that is based on the iterative method of Mehl and Hill (2002, 2004). The method is applicable to steady-state solutions for ground-water flow. Tests are presented for a homogeneous two-dimensional system that has either matching grids (parent cells border an integer number of child cells; Figure 2a) or non-matching gridsmore » (parent cells border a non-integer number of child cells; Figure 2b). The coupled grids are simulated using the finite-difference and finite-element models MODFLOW and FEHM, respectively. The simulations require no alteration of the MODFLOW or FEHM models and are executed using a batch file on Windows operating systems. Results indicate that when the grids are matched spatially so that nodes and child cell boundaries are aligned, the new coupling technique has error nearly equal to that when coupling two MODFLOW models (Mehl and Hill, 2002). When the grids are non-matching, model accuracy is slightly increased over matching-grid cases. Overall, results indicate that the ghost-node technique is a viable means to accurately couple distinct models because the overall error is less than if only the regional model was used to simulate flow in the child model's domain.« less
  • A method was developed for flexible and robust grid refinement of ground-water models that use different types of numerical methods. One application is the use of a child (local scale) finite-element model to solve for local heat and (or) solute transport by using boundary conditions derived from a parent (regional scale) finite-difference model. This paper presents a new iterative method that uses ghost nodes to link different models. The models are solved iteratively based on the shared-node method for coupling a parent model that encloses a child model described by Steffen W. Mehl and Mary C. Hill in 2002. Ghostmore » nodes are located within the parent model along a line or plane that passes through nodes of parent cells along the model interface. The links between the parent and child models-specified-flow boundary conditions for the parent model and specified-head boundary conditions for the child model-are achieved by using heads at ghost nodes and flows through the material in model cells between the child and ghost nodes. The ghost-node method can be used to link nonmatching grids that occur when parent-model cell edgedfaces do not coincide with child-model cell edgedfaces and the parent model nodes do not coincide with a ghost node. The ghost-node method is tested for two- and three-dimensional systems that are either homogeneous or moderately heterogeneous, and for matching and nonmatching grids. The coupled models are simulated by using the finite-difference MODFLOW and finite-element FEHM models for the parent and child grids, respectively. Results for models of two-dimensional, homogeneous systems having matching or nonmatching grids indicate that the new method is as accurate as coupling using shared-node method of two MODFLOW models having matching grids. The three-dimensional systems exhibit similar errors to the two-dimensional homogeneous systems with both matching and nonmatching grids.« less
  • Abstract not provided.
  • The semi-implicit method for the MHD equations is extended to grid-point models and for implementation with a more accurate time advance scheme.