For simulations that involve direct use of finite-rate chemistry, the chemistry-solution portion of the species equations is solved on a cell-by-cell basis. As a result, the equations solved are independent of the mass and volume of a specific cell. In this way, cells that have the same temperature, pressure, and initial species mass fractions will yield the same result. To take advantage of this fact, when you select the Ansys CHEMKIN-CFD Solver, Ansys Fluent uses a Dynamic Cell Clustering (DCC) method to group computational cells of high similarity into clusters using an efficient data-clustering method. That requires solution of the kinetic equations only once for each cluster. The optimal number of clusters is dynamically determined for each CFD time step. The clustering algorithm is solely based on the cell thermochemical states and is independent of their locations in the CFD mesh. In addition, the clustering algorithm is highly automated and requires minimal inputs. The algorithm uses cell temperature and equivalence ratio as the clustering indices.
The DCC method consists of three major steps:
Grouping cells into clusters using an evolutionary data-clustering algorithm.
Solving chemical kinetic equations based on cluster averaged state variables.
Mapping the cluster averaged solution back to the individual cells while preserving the initial temperature and species stratification.
Further information of dynamic cell clustering can be found in section Using Dynamic Cell Clustering in the Fluent User's Guide.