Import Mesh made in COMSOL Multiphysics

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swaroop
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Joined: 24 Jul 2010, 02:10

Import Mesh made in COMSOL Multiphysics

Post by swaroop »

Hi all:
I am new to Elmer.I tried importing the mesh made in COMSOL Multiphysics i.e .mphtxt file. However, the process was unsuccessful. Can anyone shed some light on this??

Thank you in advance
Swaroop
raback
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Re: Import Mesh made in COMSOL Multiphysics

Post by raback »

Hi

The import should be pretty straight-forward if it works. Perhaps you could attach a minimal case of the mesh for inspection. The formats evolve and the parser may not be complete as it is written using just a few .mphtxt files as the starting point. I'm not aware of any documentation of the .mphtxt file format.

-Peter
swaroop
Posts: 5
Joined: 24 Jul 2010, 02:10

Re: Import Mesh made in COMSOL Multiphysics

Post by swaroop »

Hi Peter:
Thank you for your prompt reply.
I am herewith attaching a sample mesh generated in COMSOL ver. 3.5a .
sample.mphtxt
simple comsol mesh
(41.1 KiB) Downloaded 557 times
As I said before the Elmer crashes. Also, I have other questions as I have recently started working with Elmer. I am attaching a figure of my geometry. The diameter of the circular pipes are 40 microns and 200 microns length. The 2 cuboids represent the inlet and outlet domains. I have a pressure drop instead of velocity boundary condition across the pipes. I am using SolidWorks to generate the .step file.
figure1.JPG
figure1.JPG (64.94 KiB) Viewed 6984 times
My queries are:
1) In Elmer, while setting the b.c. I entered 100 Pa(inlet) at one of the faces of the cuboid and 0 Pa (outlet) at another face of the second cuboid (i.e 100Pa drop).In addition to this, I kept the text box of "External Pressure" for both inlet and outlet blank. Is it alright or should I enter the atmospheric pressure?I have attached the geometry imported in Elmer.

2) I wish to see the trajectories of sand particles mixed in the fluid ( approx 100 particles randomly injected at inlet). is it possible to achieve this in Elmer? if yes please help.

3) I am using the inbuilt post- processor in Elmer. I want to inspect velocity field at particular plane(i.e Slice view) through the center of the channels to check the results. I was able to get it in COMSOL and Ansys. Could you tell me how to do this in Elmer? I am attaching a figure of the plot as generated by COMSOl.
Slice view in comsol of velocity field
Slice view in comsol of velocity field
comsol_slice_view.jpg (65.86 KiB) Viewed 6984 times
Thank you in advance,
Swaroop
raback
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Re: Import Mesh made in COMSOL Multiphysics

Post by raback »

Hi

I have no problems with your sample. There was however a bug fix in sif generation so you might update your version.

Comsol often uses quadratic elements but the mesh in .mphtxt file is still just linear. Judging on the smooth velocities here it may be the case here too. This means that the results with the linear mesh wont be comparable in accuracy.

1) The standard discretization prefers the "External Pressure" to "Pressure". The defaut is zero (natural BC) and for incompressible flow only the dP has an effect.

2) Sort off. There is an experimental solver for doing this. See more info in http://elmerfem.org/forum/viewtopic.php?f=15&t=505
The most recent code is in the svn so you might use it if you want to try out. Many viz software such as Paraview support particle tracking so that's onother option.

3) Yes. Choose Isosurface and some coordinate as "Contour Variable" and the field as "Color Variable".

-Peter
swaroop
Posts: 5
Joined: 24 Jul 2010, 02:10

Re: Import Mesh made in COMSOL Multiphysics

Post by swaroop »

Thank you Peter for detailed explanation. I will try them out ASAP.
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