## 3.4. Using the CFX-Interpolator

The CFX-Interpolator allows the results from one or more results files (the "source files") to be used as initial conditions for a run defined in a single Solver Input File (the "target file"). Although it will often be used where interpolation of results from one mesh to another is required, it can also deal efficiently with cases where no interpolation is required (the source file(s) have the same mesh as the target file), and can also be used for cases where physics and other setup information is different between the source and target files.

The CFX-Interpolator can also be used to calculate the differences between two results files. This is discussed in Using the CFX-Interpolator to Calculate Difference Variables. The rest of this section considers only the use of the CFX-Interpolator to provide initial conditions.

To be able to run, the CFX-Interpolator must be given the names of the source and target files, and it outputs data in two places:

- it writes variables and other appropriate data to the target file

- it writes diagnostic information to a text output.

The most common way to use the CFX-Interpolator is to choose to specify one or more Initial Values Files as set on the Run Definition tab, either in CFX-Pre or in the CFX-Solver Manager. Unless the `Use Mesh From` option is set to `Initial Values`, the CFX-Interpolator will always be used to extract the results from the Initial Values Files for use in the new run (you do not need to explicitly select to use it). In this case, the target file itself is never seen directly by you (it is written in the CFX-Solver working directory and deleted at the end of the run) and the text output is written to the CFX-Solver Output file.

If you want to manually use the interpolator to write variables into a specific CFX-Solver Input file (not as part of a Run Definition) then you can choose Tools > Interpolate Results from the CFX-Solver Manager. In this case the specified Mesh File is used as the target file, and will be modified by the interpolation process. The text output is written into the CFX-Solver Manager's Interpolation window. You can then run the resulting target file in the CFX-Solver, using the variables written into the target file by the CFX-Interpolator as the initial conditions for the run.

You can also run the CFX-Interpolator manually using the `cfx5interp` command on the command line. See Using the Command Line to Interpolate Results in the CFX-Solver Manager User's Guide for details. In this case the target file is the file specified by the `-mesh` argument, and the text output is written to the command line window.

The following topics are discussed:

- Interpolating from a Single File
- Interpolating from Multiple Files
- Interpolation Mapping
- Adjusting the Bounding Box Tolerance
- Interpolating Onto a Solver Input File with Results Fields
- Miscellaneous Limitations of the CFX-Interpolator
- Using the CFX-Interpolator to Calculate Difference Variables

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