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A Modular Finite-Element Model (MODFE) for Areal and Axisymmetric Ground-Water-Flow Problems, Part 2: Derivation of finite-element equations and comparisons with analytical solutions

U.S. Geological Survey, Techniques of Water-Resources Investigations, Book 6, Chapter A4

by Richard L. Cooley


Table of Contents

Abstract

Introduction

Purpose and scope

Acknowledgment

Finite-element formulation in Cartesian coordinates

Governing flow equation and boundary conditions

Finite-element discretization

Derivation of finite-element equations

Error-functional justification for the finite-element equations

Integral approximations

Rotation of coordinate axes

Evaluation of spatial integrals

Example of equation assembly

Evaluation of time integral

Mass-balance calculation

Extensions of the basic equations

Unconfined flow

Drying and resaturation of nodes

Combined confined and unconfined flow

Point head-dependent discharge (springs and drainage wells)

Areal head-dependent leakage combined with aquifer dewatering

Areal head-dependent discharge (evapotranspiration)

Line head-dependent leakage combined with aquifer dewatering

Leakage of water stored elastically in a confining unit (transient leakage)

Finite-element formulation in axisymmetric cylindrical coordinates

Governing flow equation and boundary conditions

Finite-element discretization

Derivation of finite-element equations

Finite-element formulation for steady-state flow

Linear case

Nonlinear case

Solution of matrix equations

Definition of matrix equation

Symmetric-Doolittle method

Modified incomplete-Cholesky conjugate-gradient method

Generalized conjugate-gradient method

Modified incomplete-Cholesky factorization

Stopping criteria

Comparisons of numerical results with analytical solutions

Theis solution of unsteady radial flow to a pumped well

Hantush solution of unsteady radial flow to a pumped well in a leaky aquifer

Moench and Prickett solution for conversion from confined to unconfined flow near a pumped well

Steady-state flow through a dam with areal recharge

Two-dimensional steady-state flow in an unconfined aquifer

Summary

References cited

Appendix A

Notation

 


 

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