First OpenFOAM assignment

Implement a backwards facing step in OpenFoam using the icoFoam solver. Use expansion factor of 2 and Re=200 (stable) and Re=1000 (unstable). See, e.g., http://www.cavityflow.com/backwardfacingstep/backwardfacingstep.htm.

The high Re case should be unstable with default numerical methods in OpenFoam. Make a more suitable choice of numerical scheme for convection and compare different methods (upwind/TVD).