In the operator-splitting method for transient simulation, the chemistry-solution portion of the species equations are 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, Ansys Forte uses a Dynamic Cell Clustering (DCC) method to group computational cells of high similarity into clusters using an efficient data-clustering method and 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 cells' thermochemical states and is independent of their locations in the CFD mesh. In addition, the clustering algorithm is highly automated and requires minimal user-provided inputs. For typical hydrocarbon combustion computation, cell temperature and equivalence ratio are employed as the clustering indices. The only user-provided control parameters are the maximum dispersions of temperature and equivalence ratio allowable in each cluster. Smaller values will result in a larger number of clusters.

The DCC method includes three major steps: (1) grouping cells into clusters using an evolutionary data-clustering algorithm; (2) solving chemical kinetic equations based on cluster averaged state variables; and (3) mapping the cluster averaged solution back to the individual cells while preserving the initial temperature and species stratification.

In Ansys Forte, if only one clustering feature is selected, temperature will be the feature. If two features are selected, both temperature and equivalence ratio will be used by default.