The option known as dynamic adaptive chemistry is based on the dynamic application of on-the-fly mechanism-reduction and may be used with the transient solution algorithm. This method is useful in applying very large chemical mechanisms for combustion systems, for example. Controls for end-users are provided to determine the accuracy threshold for the reduction, but default values have been shown to be quite accurate. The Dynamic Adaptive Chemistry method (Liang, Stevens et al. 2009 [1]) is used to perform on-the-fly mechanism reduction for each local condition prior to solving the chemistry terms in the transient chemistry integration step of the operator-splitting method described above. The reduction is dynamically applied cell-by-cell at each time step. In this way the dynamic chemistry solution often uses locally valid, smaller mechanisms instead of the full mechanism, causing significant time savings for the overall transient integration.

To ensure accuracy over a wide range of thermochemical conditions, detailed kinetic mechanisms for simulating the combustion of realistic fuels typically include hundreds of species and thousands of elementary reactions. However, much smaller subsets of species and reactions often are adequate to capture the dominant reaction pathways for specific, local conditions over a short time span (typically taken to be the hydrodynamic time step in CFD calculations). To make use of this fact, the dynamic adaptive chemistry (DAC) method reported by Liang et al. [1]) has been added to the Ansys KINetics API for use with transient simulations. The DAC method reduces the detailed mechanism to locally valid smaller mechanisms on the fly (that is, during the simulation and at every time step). It is based on the directed-relation-graph with error propagation (DRGEP) method [2][1]), which offers efficient linear-time reduction.