Imposed Dirichlet condition on labelled surfaces

General Discussion
1

Dear all,
considering the " Newton Method for the Steady Navier-Stokes equations" example below:
https://doc.freefem.org/tutorials/navierStokesNewton.html
I’m wondering how to impose velocities on labelled surfaces if 3D meshes are considered. The meshing and the labelled surfaces are created using Gmsh application.
Any comment is welcome

2

you can follow Import 3D mesh files into FreeFEM - Part 1 · Mojtaba Barzegari

3

Thanks for the reference

4

my point was related on the unknowns of the problem.
The reference

https://doc.freefem.org/tutorials/navierStokesNewton.html

considers the displacement increments du as unknowns, and I do not see how to impose a condition on displacements u

5

With regards to the document navierStokesNewton, instead of imposing du1=0, du2=0 , if you want to impose the Dirichlet condition on the updated velocities u_1^{i+1}=a, u_2^{i+1}=b, the best way is to write + on(1, du1=u1-a, du2=u2-b)

6

Thanks François,
by the fact, I already tried this but I did not let enough iterations running, so my conclusions were erroneous.
You have confirmed the approach, so I let more iterations progressing, and it’s better now.