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Re: pressure spikes in Stokes demo?

 

Something went wrong at changeset 4224,

  http://www.fenics.org/hg/dolfin?cs=c5a7da38ff2c

Garth

ndl@xxxxxxxxxxxxxx wrote:
On Monday 16 June 2008, Anders Logg wrote:
On Mon, Jun 16, 2008 at 05:40:00PM +0100, Nuno David Lopes wrote:
Is this problem really solved?
No, it looks awful here as well. It used to look much better.

I'm get oscillating spikes  all over the boundary.
The same for a standard 2d cavity.
For which element types are you getting the spikes?
in 2D the same as in demo: triangle Lagrange 2 for velocities and Lagrange 1 for pressure.

Also in 3d experiments.
I'm getting  the feeling that only the the dofs associated with the
triangle vertices are getting the boundary conditions, (or something like
that is happening.)
Can you check for which degrees of freedom we are enforcing
boundary conditions? Are we missing any?
I will try to get into that  first thing tomorow. I hope i'll understand it!!!
I think I've seen something similar some time ago, don't remember if it was in my old hand-made c++ codes, using Uzawa methods, or in FreeFem++ also with Uzawa methods, but i've solved it and I really don't remember what was the problem.





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