## Chapter 15: Initialization

Initialization is the process by which all unspecified solution field values are assigned at the beginning of a simulation. These values are commonly referred to as initial values. For steady-state simulations, they may be collectively referred to as an initial guess.

For steady-state simulations, initial values can be set automatically if a good initial guess is not known or is not required. Although accurate initial values may not always be available, a good approximation can reduce the time to solve a steady-state simulation and reduce the chance that the solution fails to converge due to diverging residuals. The more complicated the simulation and models used, the more important it becomes to start the solution process with sensible initial values. Advice about choosing sensible initial values is available in Initialization Parameters in the CFX-Solver Modeling Guide.

For transient simulations, the initial values must be specified for all variables because the data describes the state at the simulation start time.

If available, the results from a previous simulation can be used to provide the initial values. In this case, any values chosen to be automatically set will be overridden by values from the initial values file(s). See Reading the Initial Conditions from a File in the CFX-Solver Modeling Guide for details.

Global and domain initialization settings may be specified. Global settings apply to only those domains that do not have their own initialization settings.

Information on modeling initial values is available in Initial Condition Modeling in the CFX-Solver Modeling Guide.

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