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

**URL:** <https://community.freefem.org/t/difference-between-vtu-output-file-and-the-values-from-freefem-for-a-stokes-problem/3755>\
**Category:** General Discussion\
**Created:** [February 17, 2025, 9:52am UTC](https://community.freefem.org/t/difference-between-vtu-output-file-and-the-values-from-freefem-for-a-stokes-problem/3755 "2025-02-17T09:52:23Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Pwaroquier](https://avatars.discourse-cdn.com/v4/letter/p/91b2a8/32.png) [@Pwaroquier](https://community.freefem.org/u/Pwaroquier)\
**Post date:** [February 17, 2025, 9:52am UTC](https://community.freefem.org/t/difference-between-vtu-output-file-and-the-values-from-freefem-for-a-stokes-problem/3755/1 "2025-02-17T09:52:23Z")

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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](https://canada1.discourse-cdn.com/flex030/uploads/freefem/original/2X/8/8b086fb1e1b05f672850f47123a5f9967b501df0.png)

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

 ![image](https://canada1.discourse-cdn.com/flex030/uploads/freefem/original/2X/3/34936df31851f1b9bc6ace30bde7535ce00c8ba6.png)

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](https://community.freefem.org/uploads/short-url/cQLNtpsvX61HMWctshjQ29Qd1Rg.edp) (2.2 KB)

Thanks in advance,  
Pierre