Metafor

Geometry and mesh definition

The first step is of course defining the geometry of the problem and mesh it. For the time being the geometry and the mesh are defined using Gmsh and then imported by POL(I)FLOWS through the input file (see Geometry and mesh import section).

NB: Please note that for the moment only triangular meshes are used by POL(I)FLOWS: other kinds of elements can be imported without errors BUT they won't be used for the finite element computations!!!

## Problem definition: the input file

All the problem features, together with the simulation parameters and options, have to be defined in a Python input file. The input file represents the way the user can provide the software with all the information needed. Details on how the input file has to be written are expained in the Input file section.

## Running the simulation

The simulation can be run very easily just by opening a command window, navigating to the directory where the input file is and taping:

``` python input_file_name.py ```

NB: in order to proceed in this way, the user has to make sure of two things: - a Python interpreter is present on the machine; - the Pyhton interpreter is available in the path (see e.g. https://docs.python.org/2/using/windows.html).

## Results gathering and post-processing

In this section some basic information on the results that can be obtained from a simulation and on the way they can be post-processed is given. In order to better understand which kind of data can be archived, and how, please refer to Results archiving section.

Generally speaking, three kinds of result files can be stored during a simulation at this stage:

- `.res` files, which contain global information related to the simulation: geometry, mesh, data at nodes, etc… These files can be read by Gmsh and are mainly useful for the visual treatment of the results, i.e. for visualising the geometry and mesh evolution, velocity and pressure fields, create figures or videos of the simulation, … ;

- `.ascii` files which contain many different types of data, ranging from the time evolution during the simulation to the forces acting on the body at specific points or physical entities (e.g. on a specific boundary). These files are particularly useful for the plot of curves, i.e. for the creation of graphs. The kind and location of data to be stored in these files are chosen by the user (see Results archiving section);

- `.vtk` files: these files are similar to `.res` files, but they are created only if the graphic user interface (GUI) is used (see the POL(I)FLOWS-GUI section). They can be easily read and processed using, for example, Paraview. The advantage, with respect to `.res` files, is that their processing in Paraview is much lighter than the one of `.res` files in Gmsh.

Now, if you're curious and you want to run a simulation with POL(I)FLOWS, the only thing you're missing is knowing how to write a proper Input file…