Within a reactor model that enables Particle Tracking, the simulation treats a particle population as a collection of tiny solid or liquid material pieces suspended in bulk gas. This dispersed material concept represents the fact that particles are in a condensed phase and also allows use of existing surface-kinetics capabilities to handle gas-particle interactions.

Since the particles represent a condensed-phase material, all particle-related definitions are included in the surface chemistry input file. To declare a dispersed material, the Surface Kinetics keyword MATERIAL must be provided at the top of the Surface Kinetics Input file. This allows assignment of a name to the surface material. This material can then be designated as a dispersed material (that is, it will be tracked in particle form), using the keyword DISPERSED that follows the MATERIAL statement. For example,

MATERIAL soot
DISPERSED
END

With this entry, the material "soot" will be recognized by Ansys Chemkin as a dispersed material. Note that an END keyword is needed to close the DISPERSED keyword block, although at this time there is no additional information included in the block.

It is possible to have more than one type of particle co-exist in the same system, although currently the Particle Tracking equations do not consider interactions between different types of particles. Different types of particles are defined as different dispersed materials. Definitions of multiple dispersed or non-dispersed materials are separated by the MATERIAL keywords. For example, if a chemical system contains two types of particles, such that one is called soot and the other is called silicon, they should be declared in two separate MATERIAL blocks as illustrated in Figure 6.2: Example of Two Material Blocks .

MATERIAL soot
DISPERSED
END
REACTIONS
…
END
MATERIAL silicon
DISPERSED
END
REACTIONS
…
END