I am trying to re-create results from tutorial 3.2 Incompressible NS equations. I do not understand where the dx comes from in part  writing Stokes bilinear form. How to adjust that value?
When I set it to 1.0, I can not reproduce the lift graph exactly as it is shown in the tutorial. When I set it to some value below 1.0 scheme gets unstable and when I set it to some value above 1.0, say 1.1, the scheme runs without being unstable but again I can not reproduce neither drag nor lift graphs as it is shown in the tutorial.
Thanks in advance.