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Meshing of boundary layers wont work

Posted Mar 21, 2011, 4:54 a.m. EDT Fluid & Heat, Heat Transfer & Phase Change, Computational Fluid Dynamics (CFD), Mesh Version 4.2a, Version 4.3b 3 Replies

Christian Kelb
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I am trying to mesh (and, eventually, compute) a model of a rectangular duct connected to a circular hole, where the duct and the lower part of the hole are filled with water, the upper part of the hole is filled with air, initially. For better monitoring of the boundarys i am using the "boundary layer"-Function of comsol to increase the tightness of the mesh.

However the meshing stops with the error-message "Could not shift boundary node at all" which leaves me clueless because i dont know which boundary node could be meant or how to solve this issue.

Can anyone help me?

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3 Replies Last Post Aug 28, 2014, 10:46 a.m. EDT
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Mar 21, 2011, 6:55 a.m. EDT
Hi

You could try to cut your volumes in sections with some interiour boundaries, this often helps the meshing



--
Good luck
Ivar
Hi You could try to cut your volumes in sections with some interiour boundaries, this often helps the meshing -- Good luck Ivar
Yoav Matia
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Posted: 1 decade ago Jun 6, 2013, 4:22 a.m. EDT
Hi there
here is the solution for you:

Prelude:
I to have encountered that same error so many times when i modeled 3D geometries yet almost never when modeling 2D geometries. Why?
COMSOL is trying to patch over the sharp corner diagonally in order to better/more smoothly mesh over the geometry in a way that will enable better representation of flow gradients over a corner.
all that is excellent and another reason why i have so much appreciation for COMSOL developers as they are actual Mathematics/Engineering/Physics professionals.
however, the problem is that doing this sort of "patching" is quite simple in 2D but very difficult in 3D, unless the geometry is very specific and of the kind that will not bring the meshing algorithm into collapse upon itself (due to impossible clustering of such elements).

(remainder: the higher the physics-gradient present at geometrical location, the denser the mesh you will need to "capture" and depict that phenomena using FEM, for reasons related to Element order).

Solution:
all you need to do is:
Ver 4.2a ==> uncheck the split boundary layer check box (see pictures attached)
Ver 4.3B==> choose the trimming option from the drop menu /Engineering

works for me every time :)
Hi there here is the solution for you: Prelude: I to have encountered that same error so many times when i modeled 3D geometries yet almost never when modeling 2D geometries. Why? COMSOL is trying to patch over the sharp corner diagonally in order to better/more smoothly mesh over the geometry in a way that will enable better representation of flow gradients over a corner. all that is excellent and another reason why i have so much appreciation for COMSOL developers as they are actual Mathematics/Engineering/Physics professionals. however, the problem is that doing this sort of "patching" is quite simple in 2D but very difficult in 3D, unless the geometry is very specific and of the kind that will not bring the meshing algorithm into collapse upon itself (due to impossible clustering of such elements). (remainder: the higher the physics-gradient present at geometrical location, the denser the mesh you will need to "capture" and depict that phenomena using FEM, for reasons related to Element order). Solution: all you need to do is: Ver 4.2a ==> uncheck the split boundary layer check box (see pictures attached) Ver 4.3B==> choose the trimming option from the drop menu /Engineering works for me every time :)
SMHH
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Posted: 10 years ago Aug 28, 2014, 10:46 a.m. EDT
Thanks Yoav. Your trimming solution worked very well.
Thanks Yoav. Your trimming solution worked very well.

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