VENT2D is a two-dimensional, finite difference, multi-compound vapor transport and phase partitioning model. The program solves the vapor-phase advective and diffusive fluxes of up to 60 compounds in a 35 x 35 grid. The chemical compounds can partition into the vapor, dissolved, adsorbed and (if concentrations are high enough at a given location) a nonaqueous phase liquid (NAPL). Since the NAPL means non-linear sorption, the phase distribution must be explicitly calculated at each node between vapor movement timesteps. Henry's Law dictates phase partitioning without NAPL, while Raoult's Law is used when NAPL is present. The vapor is assumed to be the only mobile phase. The 2-D grid can be given any distribution of permeability and initial contaminant concentrations. The model continuously tracks the water and NAPL saturations to update the soil-gas permeability, pressure and flow fields. The 2-D grid also allows spatially-variable leakage of clean air from the third dimension into the model domain (simulating a bare ground surface, for example). The transport code was developed specifically for vapor movement and is much faster than an equivalent groundwater transport code. Since vapor diffusion is usually much more dominant than hydrodynamic (aerodynamic?) dispersion, the simpler diffusion is solved exclusively. Of course, the diffusivity is saturation dependent. Extraction or injection wells can be specified at any grid location. A spreadsheet containing the chemical characteristics (required by VENT2D) of gasoline hydrocarbons and other organic compounds is provided in the acces.zip file.
VENT2D Version 2.2 requires a '486 or Pentium (TM-Intel Corp.) machine with 2 Mb RAM.