This Application Guide is a software document written to provide a suite of example applications of the STOMP (Subsurface Transport Over Multiple Phases) simulator, a scientific tool for analyzing multiple phase subsurface flow and transport. A description of STOMP'S governing equations and constitutive functions and numerical solution algorithms are provided in a companion document, the STOMP Theory Guide. The use, compilation, and execution of the STOMP simulator are described in a second companion document, the STOMP User's Guide. Creation of input files for the STOMP simulator with the sTeP utility is described in a third companion document, the sTeP User's Guide. In writing these guides to the STOMP simulator, the authors have assumed that the reader or code user has received training or is knowledgeable on the topics of multiple phase hydrology, thermodynamics, radioactive chain decay, and nonhysteretic relative permeability-saturation-capillary pressure (k-S-P) functions. The authors further assume that the reader is familiar with the computing environment on which they plan to compile and execute the STOMP simulator. Computer requirements for the STOMP simulator are strongly dependent on the complexity of the simulated system and the translation of the physical domain into a computational domain. The simulator requires an ANSI FORTRAN 77 compiler to generate an executable code. The speed at which the STOMP simulator solves subsurface flow and transport problems depends on the computing platform, problem complexity, and computational domain size and dimensionality. One-dimensional problems of moderate complexity can be solved on conventional desktop computers, but multidimensional problems involving complex flow and transport phenomena typically require the power and memory capabilities of workstation or mainframe computer systems. Pacific Northwest National Laboratory is operated for the U.S. Department of Energy by Battelle Memorial 1 Institute. under Contract DE-AC(M76RL01830. V Acknowledgments This work was funded by the Office of Science and Technology, within the Department of Energy's Office of Environmental Management, under the Plumes Focus Area, with the support of

, the Pacific Northwest Laboratory has been conducting a geohydrologic in

Solute transport simulation using numerical models is an important and widespread tool for evaluation of clean‐up strategies as well as for prediction of future transport. Classical simulation algorithms for advective‐dispersive transport usually introduce large numerical errors where concentrations are lowest. In general, numerical errors tend to spread (disperse) the solute more than physical processes alone. For simulations where the Peclet number (Pe) is greater than about 2, numerical dispersion can be very significant and could lead to erroneous conclusions. Recent numerical techniques for simulating advective transport minimize numerical errors and provide much better solutions. One such technique, Flux‐Corrected Transport (FCT), can preserve sharp concentration fronts by virtually eliminating numerical dispersion. In general, it has been observed that as more detailed knowledge of subsurface flow fields is obtained, smaller dispersivity values are needed to match observed and simulated data. However, for many numerical codes the use of small dispersivities is not practical, because it requires fine grids to keep the grid Peclet number limited. A general purpose transport code, PMFCT‐2D, has been developed, including a fast and efficient FCT algorithm, to simulate advective‐dispersive transport in variably saturated, heterogeneous porous media, with nonuniform aquifer thickness in the third dimension. PMFCT‐2D can be used to accurately simulate high Peclet number transport, including purely advective transport (Pe =∞), resulting from transient or steady‐state flow conditions. The code is easily coupled to any flow simulator via generated velocity, saturation, and cell thickness fields.