16.5.3 Zeroing Species in the Initial Unsteady Flamelet

When modeling gas-phase combustion using the Eulerian unsteady laminar flamelet model, the flamelet fields are initialized to a burning, steady-flamelet solution in order to model ignition. However, assuming steady-flamelet profiles for slow-forming species is inaccurate. A better approximation is to identify the slow species and to set them to zero, which is done in the Control tab. By default, ANSYS FLUENT selects some NOx species ( $NO$, $NO_2$, $N_2O$, $N$, $NH$, $NH_2$, $NH_3$, $NNH$, $HCN$, $HNO$, $CN$, $H2CN$, $HCNN$, $HCNO$ $HOCN$ $HNCO$ $HCO$), as well as liquid water $H_2O<l>$ and solid carbon $C<s>$ to be zeroed. See Figure  16.5.3.

Figure 16.5.3: Method to Zero Out the Slow Chemistry Species