## 3.1. Files Used by the CFX-Solver

The CFX-Solver input file usually contains all the information that is required by the CFX-Solver to run a CFD simulation. This information includes:

- Physical models and fluid property settings

- Boundary conditions

- Initial conditions

- The mesh

- CFX-Solver parameter settings.

However, there are circumstances when the file specified in the Solver Input File option (referred to hereafter as the Solver Input File) requires additional solution values to initialize the run. These additional initial solution values are introduced by defining one or more Initial Values objects, each of which refers to either a previously created results file or a configuration for which a results file has not yet been created. In all cases, these results files merely supplement the run with solution values that are not available in the input file; simulation specifications in the Solver Input File are not overridden.

When starting a run using results from Initial Values objects, the mesh from the Solver Input File is used by default and solution values are either copied or interpolated from the initial values mesh(es) onto the Solver Input File mesh. Additionally, when initial values files are used, the run history (that is, monitor and convergence data, simulation, time and timestep counters) is continued by default. You may also choose to not continue the run history.

The following tables describe the behavior resulting from different combinations of Solver Input File and Initial Values objects for single and multi-configuration simulations.

Single Configuration Simulations
Solver Input File | Initial Values Specification | Description
--- | --- | ---
CFX-Solver Input file (`.def`) |  | New simulation (that is, no run history) starting from iteration or time step # 1.
CFX-Solver Results (`.res`) |  | Continue simulation (solution values and run history), starting from the iteration or time step that follows last completed in the previous run[ 1 ].
CFX-Solver Input (`.def`) | Initial Values object(s) using the Results File option that references a CFX-Solver Results file (`.res`, `.trn`, `.bak`). | Supplement initial conditions in the Solver Input File with solution values contained in the results file referenced by the Initial Values object(s).

Multi-Configuration Simulations
Solver Input File | Configuration-Specific Initial Values Specification | Description
--- | --- | ---
CFX-Solver Input file (`.mdef`) |  | New simulation (that is, no run history) with all configuration analyses starting from iteration or time step # 1.
CFX-Solver Input file (`.mdef`) | Initial Values object(s) using the Results File option that references a CFX-Solver Results file (.res, .trn, .bak). | Supplement initial conditions in configuration definitions with those contained in the results file(s) referenced by the Initial Values object(s).
CFX-Solver Input file (`.mdef`) | Initial Values object(s) using the Configuration Results option that references a configuration. | Supplement initial conditions in configuration definitions with solution values contained in the latest results file corresponding to the configuration(s) referenced by the Initial Values object(s).
CFX-Solver Results file (`.mres`) |  | Continue simulation (solution values and run history), starting from configuration that follows the one last completed in the previous run. The simulation will proceed to complete the last configuration being executed in the previous run if the simulation was stopped prematurely (for example, via the `cfx5stop` command). Note that this is the only way to continue a multi-configuration simulation[ 1 ].

Footnote:

1. If you explicitly select a solver results file that was generated by a multi-configuration run to be the solver input file, the name of the new monitor workspace in CFX-Solver Manager is inherited from the state stored in the configuration results.

It is important to note that for multi-configuration simulations:

- Global (or simulation) level Initial Values specifications are not valid

- A configuration level Solver Input File is implied in the multi-configuration setup (that is, it is not required).

Other important considerations to note are:

- Setting the Initial Values Specification > Use Mesh From option to Solver Input File will activate the CFX-Interpolator to either copy or interpolate solution values from the mesh in the Initial Values object(s) to the Solver Input File. See Using the CFX-Interpolator in the CFX-Solver Modeling Guide for details.

- Setting the Initial Values Specification > Use Mesh From option to Initial Values will use the mesh from the Initial Values File and de-activate the CFX-Interpolator. See Using the Mesh from the Initial Values File in the CFX-Solver Modeling Guide for details.

- Unsetting (that is, deselecting) the Initial Values Specification > Continue History From option will reset the run history and use the Initial Values File to provide a basic initial guess for the new run. See Continuing the History in the CFX-Solver Modeling Guide for details.

- Setting the Initial Values Specification > Continue History From option will continue the run history from the results file referenced by the specified Initial Values object, and produce the cleanest restart possible from the Initial Values File. The first iteration or timestep executed follows the last one completed in the referenced results file. See Continuing the History in the CFX-Solver Modeling Guide for details.

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