hst3d(1) U.S. Geological Survey (wrdapp) hst3d(1) NAME hst3d - Three-dimensional flow, heat, and solute transport model ABSTRACT The Heat- and Solute-Transport Program (HST3D) simulates ground- water flow and associated heat and solute transport in three dimensions. The HST3D program may be used for analysis of problems such as those related to sub-surface-waste injection, landfill leaching, saltwater intrusion, freshwater recharge and recovery, radioactive-waste disposal, hot-water geothermal systems, and subsurface-energy storage. The three governing equations are coupled through the interstitial pore velocity, the dependence of the fluid density and fluid viscosity on pressure, temperature, and solute-mass fraction. The solute-transport equation is for only a single, solute species with possible linear-equilibrium sorption and linear decay. Finite-difference techniques are used to discretize the governing equations using a point-distributed grid. The flow-, heat- and solute-transport equations are solved sequentially after a partial Gauss-reduction scheme is used to modify them. The modified equations are more tightly coupled and have better stability for the numerical solutions. The basic source-sink term represents wells. A complex well-flow model may be used to simulate specified flow rate and pressure conditions at the land surface or within the aquifer, with or without pressure and flow-rate constraints. Boundary-condition types offered include specified value, specified flux, aquifer and river leakage, heat conduction, an approximate free surface, and two types of aquifer-influence functions. All boundary conditions can be functions of time. Two linear equation solvers are available for solution of the finite-difference matrix equations. One is a direct-elimination solver, using equations reordered by alternating diagonal planes. The other is an iterative solver, using a generalized conjugate- gradient method. A restart option is available for storing intermediate results and restarting the simulation at an intermediate time with modified boundary conditions. This feature also can be used as protection against computer-system failure. Data input and output may be in metric (SI) units or U.S. customary units. Output may include tables of dependent variables and parameters, and output files designed for use by post-processing programs for graphical visualization and for flow totalization. There is a preprocessor for evaluating dimensioning requirements and a postprocessor for totalizing boundary flow rates and cumulative amounts. The post-processing program for graphical visualization must be supplied by the user. Version 2 of the simulator has been verified using five test problems selected from the published literature. One involves heat transport, four involve solute transport, and all have variable- density fluids. 10 June 1999 1 hst3d(1) U.S. Geological Survey (wrdapp) hst3d(1) METHOD HST3D simulates heat and solute transport in three-dimensional saturated ground-water flow systems. The equations that are solved numerically are: (1) The saturated ground-water flow equation, formed from the combination of the conservation of total-fluid mass and Darcy's Law for flow in porous media; (2) the heat-transport equation from the conservation of enthalpy for the fluid and porous medium; and (3) the solute-transport equation from the conservation of mass for a single-solute species, which may decay and may adsorb onto the porous medium. These three equations are coupled through the dependence of advective transport on the interstitial fluid- velocity field, the dependence of fluid viscosity on pressure, temperature, and solute concentration, and the dependence of fluid density on pressure, temperature, and solute concentration. Numerical solutions are obtained for each of the dependent variables: pressure, temperature, and mass fraction (solute concentration) in turn, using a set of modified equations that more directly link the original equations through the velocity-, density-, and viscosity-coupling terms. Finite-difference techniques are used for the spatial and temporal discretization of the equations. When supplied with appropriate boundary and initial conditions and system-parameter distributions, simulation calculations can be performed to evaluate a wide variety of heat- and solute-transport situations. HISTORY Version 2.05 1999/03/29 - Fixed ascending node range in HST3D routine HUNT, fixed cell saturation fraction in HST3D routine INIT2, made cosmetic changes in output, fixed bug in DIMEN routine READ1. Version 2.04 1999/02/09 - Fixed a conflict in temporary storage for rivers and head printouts in HST3D routines ERROR4, INIT2, READ2, WRITE2. Reduced stripped file record lengths in DIMEN routine READ1. Version 2.03 1999/01/19 - Added type declarations for some undeclared variables, added display of equation name to screen, removed some obsolete solution method indexing in HST3D routine APLBCI. Version 2.02 1998/12/15 - Fixed divide-by-zero bug in DIMEN and restart bug in HST3D; included static information in restart output files; increased input data file name length to 20 characters in HST3D, DIMEN, BCFLOW. Version 2.01 1998/10/07 - Fixed format errors in routine REWI3. Version 2.0 1998/08/18 - Various additions, modifications, and corrections. Major enhancements include: (1) a revised input file with all spatial information described by coordinate location, (2) a new iterative solver for the matrix equations based on a generalized conjugate-gradient method, (3) an 10 June 1999 2 hst3d(1) U.S. Geological Survey (wrdapp) hst3d(1) evapotranspiration boundary condition, (4) a division of the simulator output into many files, (5) a new set of output files designed for use by post-processing programs for graphical visualization and for flow totalization, (6) a preprocessor for evaluating dimensioning requirements, and (7) a postprocessor for totalizing boundary flow rates and cumulative amounts. Version 1.4 1989/05 - Several minor additions. Version 1.2 1987/08 - Bug fixes and added dump files. Version 1.1 1987/05 - Bug fixes. Version 1.0 1987/04 - Initial release DATA REQUIREMENTS One input data file is required. See documentation for detailed explanation of input file structure. The input file has two general characteristics: (1) it is free format for ease of preparation, and (2) it may be freely commented for rapid identification of the data items. To simplify the preparation of the input file, a template file containing only comments, Data.frm, is distributed with the software. OUTPUT OPTIONS The various types of output produced by the HST3D program are generally written to ASCII text files. The one exception is the optional check-point/restart dump written in binary format. Output is generated at several stages during the simulation. Some information, such as the heading, title, array-partitioning data, and problem-geometrical information, is always printed. The heading contains the program version number. The units employed for the output are the same as those used for the input data, either metric or U.S. customary. Much of the output is optional. The static data that may be printed include porous-media properties, fluid properties, initial-condition distributions, boundary-condition information, solution-method information, well information, and density and viscosity distributions. The initial conditions of the dependent variables (pressure, temperature, mass fraction) can selectively be printed. Print intervals can be selected individually for information that is printed at the end of a time step. The information printed may include the velocity distribution, the density and viscosity distributions, the solution method information, the conductance and dispersion-coefficient distributions, the dependent-variable distributions, the regional fluid-flow, heat-flow and solute-flow rates, the regional cumulative-flow results, and the specified-value boundary-condition flow rates. Data for temporal plots that may be produced by a postprocessor include well-datum pressure, well-surface pressure, well-datum 10 June 1999 3 hst3d(1) U.S. Geological Survey (wrdapp) hst3d(1) temperature, well-surface temperature, and well solute-mass fraction (or scaled-mass fraction). For observation wells, the well-datum value is taken to be the value in the aquifer cell at the well-datum level. SYSTEM REQUIREMENTS HST3D is written in Fortran 77. The code requires significant computational and system resources for execution. For example, a 44,000 node simulation requires a 10MB of memory, a 1.6MB input file, and may produce 12 MB of results. WARNING: HST3D is coded such that local variables are expected to be static (that is, local variables need to retain their values upon exit of a routine). Thus, the appropriate compiler options(s) must be specified to produce reliable results. Generally, the program is easily installed on most computer systems. The code has been used on UNIX-based computers and DOS-based 386 or greater computers having a math coprocessor. DOCUMENTATION Kipp, K.L., Jr., 1997, Guide to the revised heat and solute transport simulator, HST3D--Version 2: U.S. Geological Survey Water-Resources Investigations Report 97-4157, 149 p. Kipp, K.L., Jr., 1986, HST3D--A computer code for simulation of heat and solute transport in three-dimensional ground-water flow systems: U.S. Geological Survey Water-Resources Investigations Report 86-4095, 597 p. TRAINING Advanced Modeling of Subsurface Flow and Transport (GW3086TC), USGS National Training Center. CONTACTS Operation: U.S. Geological Survey Kenneth L. Kipp Denver Federal Center, MS 413 Denver, CO 80225 klkipp@usgs.gov Distribution: U.S. Geological Survey Hydrologic Analysis Software Support Program 437 National Center Reston, VA 20192 h2osoft@usgs.gov Official versions of U.S. Geological Survey water-resources analysis software are available for electronic retrieval via the World Wide Web (WWW) at: 10 June 1999 4 hst3d(1) U.S. Geological Survey (wrdapp) hst3d(1) http://water.usgs.gov/software/ and via anonymous File Transfer Protocol (FTP) from: water.usgs.gov (path: /pub/software). The WWW page and anonymous FTP directory from which the HST3D software can be retrieved are, respectively: http://water.usgs.gov/software/hst3d.html --and-- /pub/software/ground_water/hst3d SEE ALSO moc3d - Three-dimensional method-of-characteristics ground-water flow and transport model mocdense - A two-constituent solute transport model for ground water having variable density sutra - Saturated and (or) unsaturated, constant or variable-density fluid flow, and solute or energy transport (2-dimensional finite-element code) 10 June 1999 5