MOFAT DESCRIPTION
Introduction to MOFAT MOFAT for Windows includes a graphical preprocessor, Mesh Editor and postprocessor with online help. Simulate multiphase (water, oil and gas) flow and transport of up to five noninert chemical species in MOFAT. Model flow of light or dense organic liquids in three fluid phase systems. Simulate dynamic or passive gas as a full threephase flow problem. Model water flow only, oilwater flow, or wateroilgas flow in variablysaturated porous media. MOFAT achieves a high degree of computational efficiency by solving flow equations at each node (on the finiteelement mesh) only for phases that are undergoing changes in pressures and saturations above specified tolerances using a new adaptive solution domain method. Therefore, if NAPL is absent or exists at a residual saturation, MOFAT will locally eliminate those flow equations. MOFAT analyzes convectivedispersive transport in water, NAPL, and gas phases by assuming local equilibrium or nonequilibrium partitioning among the fluid and solid phases. MOFAT considers interphase mass transfer and compositional dependence of phase densities. A concise but accurate description of soil capillary pressure relations is used which assures natural continuity between singlephase, twophase and threephase conditions. The user can estimate soil properties using SOILPARA.
This section is extracted from the EPA Document EPA/600/291/020 May 1991: MOFAT: A TWODIMENSIONAL FINITE ELEMENT PROGRAM FOR MULTIPHASE FLOW AND MULTICOMPONENT TRANSPORT ABSTRACT This report describes a twodimensional finite elementmodel for coupled multiphase flow and multicomponent transport in planar or radiallysymmetric vertical sections. Flow and transport of three fluid phases  water, nonaqueous phase liquid (NAPL) and gas  is considered by the program which also handles cases in which gas and/or NAPL phases are absent in part or all of the domain at any given time. The program will simulate flow only or coupled flow and transport. The flow module can be used to analyze twophase flow of water and NAPL in a system with gas present but at constant pressure or explicit threephase flow of water, NAPL and gas at variable pressure. The transport module can handle up to five components which partition among water, NAPL, gas and solid phases assuming either local equilibrium interphase mass transfer or firstorder kinetically controlled mass transfer. The governing equations are solved using an efficient upstreamweighted finite element scheme. Required input for flow analyses consists of initial conditions, soil hydraulic properties, fluid properties, time integration parameters, boundary condition data and mesh geometry. Threephase permeabilitysaturationcapillary pressure relations are defined by an extension of the van Genuchten model which considers effects of oil entrapment during periods of water imbibition. For transport analyses, additional input data are porous media dispersivities, initial water phase concentrations, equilibrium partition coefficients, component densities, diffusion coefficients, firstorder decay coefficients, mass transfer coefficients (for nonequilibrium analyses) and boundary condition data. Timedependent boundary conditions for the flow analysis may involve userspecified phase heads at nodes or phase fluxes along a boundary segment with zero flux as the default condition. For transport analyses, initial conditions are specified in terms of equilibrium water phase concentrations of each partitionable component. Timedependent boundary conditions may be stipulated as equilibrium water phase concentrations in the porous medium as prescribed fluxes defined in terms of a specified concentration in the influent liquid or with zero dispersive flux specified. Program output consists of basic information on input parameters, mesh details and initial conditions plus pressure heads, saturations and velocities for each phase at every node for specified output intervals. For transport analyses, the phase concentrations at each node are output at each printout interval. 
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