### 9.9.4. Initialization

When using the Extended Coherent Flame Model (ECFM), no initialization data for the library species is required because no transport equations are solved for them. If you are modeling the formation of NO, you will need to set an initialization option for the NO component. For details, see NO Model.

#### 9.9.4.1. Mixture

You can set values for the mixture fraction mean and variance, but Automatic is fine if you do not know of sensible initial values (a value of zero corresponds to 100% oxidizer, and a value of 1 corresponds to 100% fuel).

#### 9.9.4.2. Reaction Progress

This parameter is used to specify the reaction progress variable within the domain. corresponds to fresh (unburned) gases, whereas corresponds to completely burned gases.

#### 9.9.4.3. Flame Surface Density

This parameter is used to specify the flame surface density within the domain. =0 [m^-1] corresponds to no reaction present. Unless the reaction is ignited by other means, for example, the Spark Ignition Model, it may be necessary to specify non-zero values at least in part of the region in order to start the combustion. When the Automatic option is set the default initial values are derived from the gradient of reaction progress,

where denotes the laminar burning velocity and the turbulent burning velocity according to the Zimont correlation.

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