The HYDROTHERM computer program simulates multi-phase ground-water flow and associated thermal energy transport in three dimensions. It can handle high fluid pressures, up to 1 x 10 9 Pa (10 4 atm), and high temperatures, up to 1,200 °C. This report documents the release of Version 3, which includes various additions, modifications, and corrections that have been made to the original simulator. Major changes to the simulator include: 1) the ability to simulate unconfined ground-water flow, 2) a precipitation-recharge boundary condition, 3) a seepage-surface boundary condition at the land surface, 4) the removal of the limitation that a specified-pressure boundary also have a specified temperature, 5) a new iterative solver for the linear equations based on a generalized minimum-residual method, 6) the ability to use time- or depth-dependent functions for permeability, 7) the conversion of the program code to Fortran 90 to employ dynamic allocation of arrays, and 8) the incorporation of a graphical user interface (GUI) for input and output.
The graphical user interface has been developed for defining a simulation, running the HYDROTHERM simulator interactively, and displaying the results. The combination of the GUI and the HYDROTHERM simulator forms the HYDROTHERM INTERACTIVE (HTI) program. HTI can be used for two-dimensional simulations only. HYDROTHERM originated as a standalone program that reads model specification data from input files, and writes simulation results to output files. The HYDROTHERM INTERACTIVE GUI software integrates HYDROTHERM 3 with a graphical-user-interface preprocessor and postprocessor so that simulations can be setup and run in a visual-interactive environment.
New features in Version 3 of the HYDROTHERM simulator have been verified using four test problems. Three problems come from the published literature and one problem was simulated by another partially saturated flow and thermal transport simulator. The test problems include: transient partially-saturated vertical infiltration, transient one-dimensional horizontal infiltration, two-dimensional steady-state drainage with a seepage surface, and two-dimensional drainage with coupled heat transport.
An example application to a hypothetical stratovolcano system with unconfined ground-water flow is presented in detail. It illustrates the use of HTI with the combination precipitation-recharge and seepage-surface boundary condition, and functions as a tutorial example problem for the new user.