17.4.3 Initializing the Flame Area Density

Often, it is sufficient to initialize the flame area density $\Sigma$ to 1 (laminar flame speed) everywhere and allow the unburnt mixture entering the domain from the inlets to develop. Another option for initialization is to patch an initial value of 0 (unburnt) upstream of the flame holder and a value of 10 or higher (burnt) in the downstream region (after initializing the flow field in the region).

See Section  26.9.2 for details about patching values of solution variables.