The fan consists of a radial wheel (12 blades) enclosed in two rotating discs and of the surrounding volute. The diameter of the wheel is m, the approximate diameter of the volute is m. In the above figure  the rotating wheel is distinguished by a darker blue colour. The outer engines (coloured in red and light beige) are not participating in the physics and thus neither in the numerical simulation.

As before, we start from a plain surface geometry files. These are supplied in an alternative format to STL named “OBJ”. OpenFOAM tools are able to import both these format and even several others. OBJ, unlike STL, is capable of storing also different shapes than triangles, e.g. lines and quadrangles. The ability to contain lines makes OBJ a useful format for post-processing feature edges.
Here is a list of the supplied OBJ files:

• housing.obj, inflow.obj, outflow.obj – boundary of the model
• wheel-inlet.obj, wheel-outlet.obj – interface between the rotating wheel and the rest of the geometry
• wheel-blades.obj, wheel-disc1.obj, wheel-disc2.obj – wheel geometry
• wheel-pad.obj, wheel-pivot.obj – some other rotating parts