ASTM D5880-95(2006)
(Guide)Standard Guide for Subsurface Flow and Transport Modeling (Withdrawn 2015)
Standard Guide for Subsurface Flow and Transport Modeling (Withdrawn 2015)
SIGNIFICANCE AND USE
Subsurface fluid flow modeling is a well established tool that can aid in studying and solving soil and groundwater problems.
Evaluation of more complex problems has been allowed as a result of advances in computing power and numerical analysis, yet confusion and misunderstanding over application of models still exists. As a result, some inappropriate use occurs and some problems which could be readily addressed are not.
The purposes of this guide are to introduce the basic concepts of subsurface fluids modeling and to show how models are described and categorized.
This guide should be used by practicing groundwater modelers, purchasers of modeling services, and by those wishing to understand modeling.
SCOPE
1.1 This guide covers an overview of subsurface fluid-flow (groundwater) modeling. The term subsurface fluid flow is used to reduce misunderstanding regarding groundwater, soil water, vapors including air in subsurface pores, and non-aqueous phase liquids. Increased understanding of fluid-flow phenomena is the combined result of field investigations and theoretical development of mathematical methods to describe the observations. The results are methods for modeling viscous fluids and air flow, in addition to water, that are practical and appropriate.
1.2 This guide includes many terms to assist the user in understanding the information presented here. A groundwater system (soils and water) may be represented by a physical, electrical, or mathematical model, as described in 6.4.3. This guide focuses on mathematical models. The term mathematical model is defined in 3.1.11; however, it will be most often used to refer to the subset of models requiring a computer.
1.3 This guide introduces topics for which other standards have been developed. The process of applying a groundwater flow model is described in Guide D5447. The process includes defining boundary conditions (Guide D5609), initial conditions (Guide D5610), performing a sensitivity analysis (Guide D5611), and documenting a flow model application (Guide D5718). Other steps include developing a conceptual model and calibrating the model. As part of calibration, simulations are compared to site-specific information (Guide D5490), such as water levels.
1.4 Model use and misuse, limitations, and sources of error in modeling are discussed in this standard. This guide does not endorse particular computer software or algorithms used in the modeling investigation. However, this guide does provide references to some particular codes that are representative of different types of models.
1.5 Typically, a computer model consists of two parts; computer code that is sometimes called the computer program or software, and a data set that constitutes the input parameters that make up the boundary and initial conditions, and medium and fluid properties. A standard has been developed to address evaluation of model codes (see Practice E978).
1.6 Standards have been prepared to describe specific aspects of modeling, such as simulating subsurface air flow using groundwater flow modeling codes (see Guide D5719) and modeling as part of the risk-based corrective action process applied at petroleum release sites (see Practice E1739).
1.7 This guide offers an organized collection of information or a series of options and does not recommend a specific course of action. This document cannot replace education or experience and should be used in conjunction with professional judgment. Not all aspects of this guide may be applicable in all circumstances. This ASTM standard is not intended to represent or replace the standard of care by which the adequacy of a given professional service must be judged, nor should this document be applied without consideration of a project's many unique aspects. The word “Standard” in the title of this document means only that the document has been approved through the ASTM consensus process.
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D5880 − 95(Reapproved 2006)
Standard Guide for
Subsurface Flow and Transport Modeling
This standard is issued under the fixed designation D5880; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope or software, and a data set that constitutes the input parameters
that make up the boundary and initial conditions, and medium
1.1 This guide covers an overview of subsurface fluid-flow
and fluid properties.Astandard has been developed to address
(groundwater) modeling. The term subsurface fluid flow is
evaluation of model codes (see Practice E978).
used to reduce misunderstanding regarding groundwater, soil
water, vapors including air in subsurface pores, and non- 1.6 Standards have been prepared to describe specific as-
aqueous phase liquids. Increased understanding of fluid-flow pectsofmodeling,suchassimulatingsubsurfaceairflowusing
phenomena is the combined result of field investigations and groundwater flow modeling codes (see Guide D5719) and
theoretical development of mathematical methods to describe modeling as part of the risk-based corrective action process
the observations.The results are methods for modeling viscous applied at petroleum release sites (see Practice E1739).
fluids and air flow, in addition to water, that are practical and
1.7 This guide offers an organized collection of information
appropriate.
or a series of options and does not recommend a specific
1.2 This guide includes many terms to assist the user in course of action. This document cannot replace education or
understanding the information presented here. A groundwater experienceandshouldbeusedinconjunctionwithprofessional
system (soils and water) may be represented by a physical, judgment. Not all aspects of this guide may be applicable in all
electrical, or mathematical model, as described in 6.4.3. This circumstances. This ASTM standard is not intended to repre-
guide focuses on mathematical models.The term mathematical sent or replace the standard of care by which the adequacy of
model is defined in 3.1.11; however, it will be most often used a given professional service must be judged, nor should this
to refer to the subset of models requiring a computer. document be applied without consideration of a project’s many
unique aspects. The word “Standard” in the title of this
1.3 This guide introduces topics for which other standards
document means only that the document has been approved
have been developed. The process of applying a groundwater
through the ASTM consensus process.
flow model is described in Guide D5447. The process includes
definingboundaryconditions(GuideD5609),initialconditions
2. Referenced Documents
(Guide D5610), performing a sensitivity analysis (Guide
2.1 ASTM Standards:
D5611), and documenting a flow model application (Guide
D653 Terminology Relating to Soil, Rock, and Contained
D5718). Other steps include developing a conceptual model
Fluids
and calibrating the model. As part of calibration, simulations
D4105 Test Method for (Analytical Procedure) for Deter-
are compared to site-specific information (Guide D5490), such
mining Transmissivity and Storage Coefficient of Non-
as water levels.
leaky Confined Aquifers by the Modified Theis Nonequi-
1.4 Model use and misuse, limitations, and sources of error
librium Method
in modeling are discussed in this standard. This guide does not
D5447 Guide for Application of a Ground-Water Flow
endorse particular computer software or algorithms used in the
Model to a Site-Specific Problem
modeling investigation. However, this guide does provide
D5490 Guide for Comparing Ground-Water Flow Model
references to some particular codes that are representative of
Simulations to Site-Specific Information
different types of models.
D5609 Guide for Defining Boundary Conditions in Ground-
1.5 Typically, a computer model consists of two parts;
Water Flow Modeling
computer code that is sometimes called the computer program
D5610 Guide for Defining Initial Conditions in Ground-
Water Flow Modeling
This guide is under the jurisdiction ofASTM Committee D18 on Soil and Rock
and is the direct responsibility of Subcommittee D18.21 on Groundwater and
Vadose Zone Investigations. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved July 1, 2006. Published July 2006. Originally approved contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
in 1995. Last previous edition approved in 2000 as D5880 – 95 (2000). DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/D5880-95R06. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5880 − 95 (2006)
D5611 Guide for Conducting a Sensitivity Analysis for a sumptions. The representation of a physical system by math-
Ground-Water Flow Model Application ematical expressions from which the behavior of the system
D5718 GuideforDocumentingaGround-WaterFlowModel can be predicted.
Application
3.1.12 method of characteristics—in subsurface fluid flow,a
D5719 Guide for Simulation of Subsurface Airflow Using
numerical method to solve solute transport equations by
Ground-Water Flow Modeling Codes
construction of an equivalent system of ordinary differential
E943 Terminology Relating to Biological Effects and Envi-
equations using moving particles as reference points. Also
ronmental Fate
known as the particle-in-cell method.
E978 Practice for Evaluating Mathematical Models for the
3.1.13 model—an assembly of concepts in the form of
Environmental Fate of Chemicals (Withdrawn 2002)
mathematical equations that portray understanding of a natural
E1739 Guide for Risk-Based Corrective Action Applied at
phenomenon.
Petroleum Release Sites
3.1.14 numerical methods—in subsurface fluid flow model-
3. Terminology ing, a set of procedures used to solve the equations of a
mathematical model in which the applicable partial differential
3.1 Definitions:
equationsarereplacedbyasetofalgebraicequationswrittenin
3.1.1 analytical model—in subsurface fluid flow, a model
terms of discrete values of state variables at discrete points in
that uses closed form solutions to the governing equations
space and time.
applicable to groundwater flow and transport processes.
3.1.14.1 Discussion—There are many numerical methods.
3.1.2 boundary condition—a mathematical expression of a
Those in common use in groundwater models are the finite-
state of the physical system that constrains the equations of the
difference method, the finite-element method, the boundary
mathematical model.
element method, and the analytical element method.
3.1.3 calibration (model application)—the process of refin-
3.1.15 numerical model—in subsurface fluid flow modeling,
ing the model representation of the hydrogeologic framework,
a model that uses numerical methods to solve the governing
hydraulic properties, and boundary conditions to achieve a
equations of the applicable problem.
desired degree of correspondence between the model simula-
3.1.16 output—in subsurface fluid flow modeling, all infor-
tion and observations of the groundwater system.
mation that is produced by the computer code.
3.1.4 conceptual model—an interpretation or working de-
3.1.17 random walk—in subsurface fluid flow modeling,a
scription of the characteristics and dynamics of the physical
system. methodoftrackingalargenumberofparticleswiththenumber
of particles proportional to solute concentration, and each
3.1.5 computer code (computer program)—the assembly of
particle advected deterministically and dispersed probabilisti-
numerical techniques, bookkeeping, and control language that
cally.
represents the model from acceptance of input data and
instructions to delivery of output. 3.1.18 sensitivity—in model application, the degree to
which the model result is affected by changes in a selected
3.1.6 deterministic process—a process in which there is an
model input representing hydrogeologic framework, hydraulic
exact mathematical relationship between the independent and
properties, and boundary conditions.
dependent variables in the system.
3.1.19 simulation—in groundwater flow modeling, one
3.1.7 fidelity—the degree to which a model application is
complete execution of a groundwater modeling computer
designed to be realistic.
program, including input and output.
3.1.8 finite-difference method—in subsurface fluid flow,a
numerical technique for solving a system of equations using a 3.1.20 sink—in subsurface fluid flow modeling, a process
whereby, or a feature from which, water is extracted from the
rectangular mesh representing the aquifer and solving for the
dependent variable in a piece wise manner. groundwater flow system.
3.1.9 finite-element method—in subsurface fluid flow,a 3.1.21 steady-state flow—a characteristic of a flow system
numerical technique for solving a system of equations using an where the magnitude and direction of specific discharge are
irregular triangular or quadrilateral mesh representing the constant in time at any point.
aquifer and solving for the dependent variable in a continuous
3.1.22 stochastic—in subsurface fluid flow, consideration of
manner.
subsurface media and flow parameters as random variables.
3.1.10 groundwater flow model—application of a math-
3.1.23 stochastic model—in subsurface fluid flow, a model
ematical model to represent a site-specific groundwater flow
representing groundwater parameters as random variables.
system.
3.1.24 stochasticprocess—aprocessinwhichthedependent
3.1.11 mathematical model—mathematical equations ex-
variable is random (so that prediction of its value depends on
pressing the physical system and including simplifying as-
asetofunderlyingprobabilities)andtheoutcomeatanyinstant
is not known with certainty.
3.2 For definitions of other terms used in this guide, see
The last approved version of this historical standard is referenced on
www.astm.org. Terminology D653 and Terminology E943.
D5880 − 95 (2006)
4. Summary of Guide 6.4 For the purposes of this overview, models are classified
according to their function, fidelity, construction, and math-
4.1 Modeling is a tool that can be used to evaluate many
ematical method.
groundwater problems. Models are useful for reconnaissance
6.4.1 Model Processes—Four general types of models exist
studies preceding field investigations, for interpretive studies
for the majority of problems: fluid flow, solute (contaminant)
following the field program, and for predictive studies to
transport, heat transport, and deformation (1).
estimate future field behavior. In addition to these applications,
6.4.1.1 Fluid Flow—A fluid-flow model is normally de-
models are useful for studying various types of flow behavior
scribed by one equation, usually in terms of hydraulic head,
by examining hypothetical aquifer problems.
pressure, or potential. In multiphase flow, one equation is used
4.2 Models can be described many different ways. In this
for each phase. Groundwater flow models are often used to
guide they are differentiated by flow in porous versus karst or
solve problems concerning water supply, groundwater/surface
fracturedmedia,flowinsingleormultiphase,function,fidelity,
water interactions, capture zones, and dewatering.
construction, and method of solution.
6.4.1.2 Solute Transport—Solute transport is simulated with
an equation in addition to the flow equation to solve for
5. Significance and Use
concentrationsofthechemicalspecies.Solutetransportmodels
are often used to solve problems concerning aquifer restora-
5.1 Subsurfacefluidflowmodelingisawellestablishedtool
that can aid in studying and solving soil and groundwater tion, waste injection, sea-water intrusion, and underground
storage tank releases.
problems.
6.4.1.3 Models have been developed to describe chemical
5.2 Evaluation of more complex problems has been allowed
transformations due to interactions between the fluid(s) com-
as a result of advances in computing power and numerical
position and media composition. These models, called hydro-
analysis, yet confusion and misunderstanding over application
geochemical models, do not consider the transport processes,
of models still exists. As a result, some inappropriate use
and can be subdivided into three major categories: thermody-
occurs and some problems which could be readily addressed
namic codes, distribution-of-species codes, and reaction prog-
are not.
ress codes (2). Several geochemical codes have been described
5.3 The purposes of this guide are to introduce the basic
by van der Heijde and Einawawy (3).
concepts of subsurface fluids modeling and to show how
6.4.1.4 Heat Transport—In a simple form heat flow is
models are described and categorized.
simulated with an equation in addition to the groundwater flow
equation, similar to the solute transport equation, but in terms
5.4 This guide should be used by practicing groundwater
of temperature. In a more rigorous manner, heat flow is
modelers, purchasers of modeling services, and by those
coupled with fluid flow. The equation for fluid flow must
wishing to understand modeling.
account for variable density and an additional equation is
required to represent conduction of heat through the rock and
6. Model Types
its pores. Heat transport models are often used to solve
6.1 Simulation of a groundwater system refers to the con-
problems with thermal storage, and thermal pollution. For
struction and operation of a model whose behavior approxi-
evaluating geothermal energy development multiphase flow
mates the actual aquifer behavior. Models can be described in
equations are required to consider the presence of water and
many different ways. Model description in this guide provides
steam.
logical groupings to illustrate similarities and differences
6.4.1.5 Deformation—Aquifer deformation is simulated by
between models.
combining a groundwater flow model with a set of equations
6.2 Models of subsurface flow can first be segregated into
that describes the stress/strain relation of the soil and rock
flow in porous medium flow and non-continuum (fractured and
media. Deformation models are often used to solve problems
karst) flow. Flow can then be subdivided into single phase and
with land subsidence, soil settlement, or compaction.
multiphase flow. Single phase flow includes flow of water in
6.4.2 Model Fidelity—Three general classifications of real-
the unsaturated and saturated zone. Multiphase flow includes
ism are described; screening, engineering calculation, and
un
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