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Mesh visible in solution
Posted 25 mai 2010, 11:09 UTC−4 1 Reply
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Hi all!
I'm simulating a coupled 3D problem including stokes flow and solid mechanics (there are only small displacements therefore I do not use an ALE) the get the response of a vibrating beam in a fluid. If I plot the velocity field there are slight "discontinuties" which seem to come from the mesh (see attached file, rectangle: solid, rest fluid). My question: Is this a graphical problem? I guess not, but where does it come from? I've seen this effect also in other simulations.
Does anyone have suggestions, how to solve the problem? I would prefer not to use more degrees of freedom (a denser mesh oder higher order elements), since my hardware is rather at the limit.
Thanks for any suggestions.
Philipp
I'm simulating a coupled 3D problem including stokes flow and solid mechanics (there are only small displacements therefore I do not use an ALE) the get the response of a vibrating beam in a fluid. If I plot the velocity field there are slight "discontinuties" which seem to come from the mesh (see attached file, rectangle: solid, rest fluid). My question: Is this a graphical problem? I guess not, but where does it come from? I've seen this effect also in other simulations.
Does anyone have suggestions, how to solve the problem? I would prefer not to use more degrees of freedom (a denser mesh oder higher order elements), since my hardware is rather at the limit.
Thanks for any suggestions.
Philipp
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1 Reply Last Post 26 mai 2010, 15:58 UTC−4
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Posted:
1 decade ago
Hi
my first reaction is that I find your mesh rather coarse, you should at least run once with a refinement of 1 just to evaluate the sensitivity to the mesh, but you could also reduce the order, as this would avoid any "ripples" that could come from the higher order polynomial on your rather steep step functions.
Finally does the physics allow ripples / oscillations ? or do you expet smooth transitions ? Finally FEM is there to give you some good clues of what is going on, not necesarily to model reality to the last digit.
Have fun Comsoling
Ivar
my first reaction is that I find your mesh rather coarse, you should at least run once with a refinement of 1 just to evaluate the sensitivity to the mesh, but you could also reduce the order, as this would avoid any "ripples" that could come from the higher order polynomial on your rather steep step functions.
Finally does the physics allow ripples / oscillations ? or do you expet smooth transitions ? Finally FEM is there to give you some good clues of what is going on, not necesarily to model reality to the last digit.
Have fun Comsoling
Ivar