### 9.7.2. Boundary Settings

When specifying an inlet or opening boundary condition, you will set a Mixture option based on the properties of the incoming fluid. The options available are:

#### 9.7.2.1. Fuel

This option is used when the mass fraction of the fuel component is 1.

#### 9.7.2.2. Oxidizer

This is used when the mass fraction of the oxidizer (usually air) is 1.

#### 9.7.2.3. Mixture Fraction

Use this parameter when you need to specify the reacted mixture of fuel and oxidizer (for example, in a reacted pilot flame). A value of zero corresponds to 100% oxidizer, and a value of 1 corresponds to 100% fuel.

#### 9.7.2.4. Mixture Fraction Mean and Variance

Used in conjunction with the Mixture Fraction parameter, but additionally you can specify the variance for the “unmixedness” of fuel and oxidizer. By default, the three options above imply zero variance.

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