The three 3D meshes have been created with the software ICEM, using hexahedral cells. Several steps are required to design these meshes:
Only one half of the car is modelled. The domain measures length: 12m, height: 5m, width: 2.5m. The boundary conditions are (using Fluent 5.4):
Typically a mesh contains 150 curves and 60 surfaces. The domain is then divided in 50 to 90 blocks. The complete mesh contains approx 200,000 cells. The cell size is (length*height; meter) 0.05*0.005 near the board and 0.3*0.3 far from the car (height ratio set to 1.2).
A tetra mesh was also used, but as we could not refine
it correctly it does not appear in this report. We also tried H-refinement,
but the exportation to Fluent did not work. We refined a mesh within Fluent
selecting cells with strong velocity gradient. The obtained mesh with 600,000
cells gave the same results as the standard mesh. We can therefore conclude
than the cell size used is satisfactory.