Multi-timescale and correlated dynamic adaptive chemistry and transport modeling of flames in n-heptane/air mixtures

A correlated dynamic adaptive chemistry and transport (CO-DACT) method is developed based on our previous CO-DAC method to further improve the computational efficiency of the transport properties such as the mass diffusivities, heat conductivities, and viscosities. The concept of the correlated cell groups in both time and space coordinates for chemistry and transport is proposed by using a few key phase parameters which dominate the chemistry pathways and transport coefficients. Correlated reduced chemistry and transport properties are updated dynamically by specifying different threshold values of phase parameters of correlated cell groups. For transport, the mixture averaged diffusion model is applied to calculate the transport coefficients based on the correlated groups. Only one calculation of the transport coefficients is required for all the computation cells in the same correlated group. The advantages of the CO-DACT method are that it not only provides the flexibility and accuracy for the calculation of chemistry and transport coefficients for a large kinetic mechanism but also avoids redundant calculations in time and space when the chemistry pathways and the transport coefficients are correlated due to the similarities in phase space. The simulations of premixed propagating spherical flames as well as one-dimensional diffusion flames of an n-heptane and air mixture are carried out to validate the proposed algorithm. The results show that the present CO-DACT method is not only computationally efficient (faster by two-orders of magnitudes) but also robust and accurate for large kinetic mechanisms.