Difference between .vtu output file and the values from FreeFEM for a Stokes problem

General Discussion
1

Dear all,

I am working on a Stokes problem and I found out that my velocity field on Paraview was not the same that the solution I got from FreeFEM. You can see below the difference between my correct field and the values that are saved in my .vtu file.

This is my vector with [ux, uy, p] (ux and uy were projected from P2 to P1) :

image
image664×146 4.97 KB

These are the values saved in my .vtu output. My pressure field seems fine, but not my velocity field.

image
image1331×145 6.46 KB

It seems like the values are approximated but I really do not know why. You can find here attached the code I used.

case_A.edp (2.2 KB)

Thanks in advance,
Pierre