CHARM comes in two versions. Both are available under a single license. One version is a flat terrain puff model. The other is a complex terrain grid model. The flat terrain version lends itself to fast what if analysis. Input parameters can be easily changed with the effects seen quickly. The complex terrain version is designed for more detailed analysis.
The input required for a scenario to be run is a release description and meteorological parameters. For the complex terrain version, a grid defining the region to be calculated also needs to be supplied.
Impact (concentration, thermal radiation, or explosion overpressure) history at specified locations can also be generated. The user can either double click in the window or specify a distance and angle from the release site for calculating the impact history. Both versions provide 3D displays of the impact area with maps.
The flat terrain version of CHARM is designed to simulate the release from a single source. The complex terrain version is much more complete and can handle multiple sources and species. They both provide calculations of air transport and dispersion, mechanical and vapor cloud explosions, and BLEVE, jet fire, and pool fire radiation.
Both versions include the following capabilities:
- Editor for adding/editing chemicals.
- Editor for adding maps.
- Time varying emission rates.
- Two-phase releases.
- Releases from containment, evaporating pools, and user-defined rates.
- Time varying meteorology.
- Real-time meteorology is available, if a data collection system is present.
- Import maps automatically from Yahoo.
- Export footprints in ASCII or ESRI Shape files.
- An Application Programming Interface (API) exists for incorporating all CHARM functionality into other Windows programs.
A list of the major features of the complex terrain version is:
- The effect of 3-dimensional terrain on the wind field and dispersion over an area.
- Averaging time is included in all concentration results.
- All outputs can be displayed in 3-D. This includes fires and explosions as well as concentration impacts.
- Vertical cross-sections can be displayed for the region along any user drawn line.
- Probability of Fatality (if probit parameters are provided), Dose, Toxic Load, and Thermal Dose impacts can be displayed like any other impact.
- Editor is capable of defining grids by importing DEM and land use data available over the Internet from the USGS, the Globe Project, and other sources. A variety of file formats, including DEM and GeoTiff can be read.
- Receptor height for plan views can be either in MSL altitude or altitude above surface.
- Source location can be defined as occurring over a track defined by x (longitude), y (latitude), z, and time.
- Maps can be superimposed over the 3-D terrain.
- A graphics program is available to show terrain, impacts, and maps using DirectX for more realistic displays.
- The advection/dispersion calculation is done over the 3 dimensional grid using a finite difference solution.
- A scenario and its calculations can be saved in a separate set of files so recalculation is not required.
- Multiple release sites, each with a different species, can be modeled in one run.
- Each release can be at a different time in one scenario.
- Multiple meteorological sites.
- Liquid releases can be allowed to flow with the terrain when forming pools.
- A source can be particles with a user-defined size distribution. Concentrations and deposition amount can be displayed.
- Particles can coagulate, evaporate/condense, be created from chemical reactions, and fall to the ground.
- Convective heat transfer from the surface into the plume is considered.
- Chemical reactions can be calculated. Reaction rates can vary with temperature, solar radiation, particle size, or keyed to air and water vapor.
- Chemical reactions can be edited by the user.
- The 3-D calculation grid can contain nested grids.
- The nested grids can be user defined or automatically created by CHARM.
- The 3-D grid can represent rooms, piping, or other objects not attached to the ground.
- Export grid information in ASCII and BREEZE files.
- Create Google Earth files (kml/kmz) of buildings/objects, 2D, and 3D impacts.
- Nuclear radiation impacts from nuclides in the emission.
- Nuclide and mass fraction makeup of an emission can be specified.
- Radiation rate and dose calculated and displayed in 2D, 3D, and tables.