Federico Alzamora Previtali

Seems like you are making progress!

The mesh quality is not ideal though, you would want maximum skewness to be no more than 0.7.

Regarding your Schlieren plot, if you look at the colorbar, you have a wide range of scales. I strongly suspect the skewed cells to be the culprit here, where you would get diverging values which skew the range of the solution for Schlieren. So again, go back to your mesh and see if you can improve on it.

You can still view your Schlieren results here. In the contour dialog box, uncheck the Auto-range box, and provide a lower value for the Max. Try 1 or 2 orders of magnitude beyond the minimum value, and change this until you get the contours that you expect.