# Preparation of directories and files

## Directories

This particle tracking simulation requires four subdirectories and compiled file (see below) under your working directory, $dir;&#x20;

* $dir/constant
* $dir/20000 (your CFD result)
* $dir/result
* $dir/particle
* $dir/trajectory.out

**$dir/constant** need to contain a subderectory $dir/constant/polyMesh which stores the information on the mesh geometry (for example, boundary name, combination of neighbor cells, and so on) used in a prior CFD simulation. In case of OpenFOAM user, the directory existing in the CFD simulaiton is just able to be utilized.&#x20;

**$dir/20000** contains output from a CFD simulation such as velocity (U) and pressure (p) profiles. The directory name typically corresponding to the simulation end time, such as "20000" for a OpenFOAM CFD simulation that ends at 20000. The name of the CFD result directory can be modified by specifying it in the calculation condition file, as explained in subsequent sections.&#x20;

**$dir/result** is empty before running particle tracking simulation but it is a necessary to store the results of the trajectory simulation. It is noted that this directory is often forgotten to be created since this directory is not edited at this preparation step.

**$dir/particle** need to contain two files: a file specifying the trajectory simulation conditions ($dir/particle/conditions) and a file containing initial positions and diameters for the particles ($dir/particle/particleSet). Following sections, 3 and 4 provide more details on these two files, respectively.

**$dir/trajectory.out** is same file as generated file in building process.  You can just copy the file from src and able to use it.

In the example case ($dir=\~/squareBend), you see directoryies like below picture.

<figure><img src="https://3748253677-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FEg0RbfrtCbnSe7clcmCp%2Fuploads%2FYY6F08Nmo7eqNhR7YHXF%2Fdirectory.png?alt=media&#x26;token=c6d4b2c8-360c-4920-9211-bff19811b454" alt=""><figcaption></figcaption></figure>
