Max Courant Number exploded

ali11 · January 18, 2017, 05:54

Hi all,

I am trying a simulation of venturi meter type geometry. For this, i am using pimpleFoam, after few time step there is tremendous increase of max courant Number and then program get stop.
For futher reference i am attaching geometry, error, blockMeshDict and ControlDict files.

Any suggestion is highly appreciated.

Thanks in advance

sati · January 18, 2017, 13:12

Hi,

It seems that your mesh isn't good enough : 85 max non-orthogonality is quite high.
Try to improve your mesh, and it should be better.

Regards,
Sati

sheaker · January 18, 2017, 13:56

Hello.
As sati said, You have high non-orthogonality in Your mesh.
Also... Is Your case really 54m^3? Or maybe You forgot to transform units from [mm] to [m]?

ali11 · January 20, 2017, 02:36

Thanks sati and sheaker for you response.

As i change the solver from pimpleFoam to icoFoam, simulation run well with this mesh. For this, i tried different schemes in fvSchemes file in icoFoam. I am attaching file for which my simulation going well.

Moreover, yes Sheaker, i forget to transform my geometry into mm.

Again my question, is non-orthogonality affect my simulation in pimpleFoam.

How to improve the non-orthogonality? Is different blocking strategy will improve the non-orthogonality?

Thanks

sati · January 20, 2017, 04:19

You can indeed improve your mesh with a different blocking.
You are using a single block to mesh a cylinder. This is not optimal : the cells situated at the corner of your block are very distorted. To improve that, you can use a blocking similar to the one used in the following picture :

ali11 · January 20, 2017, 05:20

thank you sati!

I got your point.

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January 18, 2017, 13:12		#2
sati New Member Join Date: Mar 2015 Posts: 16 Rep Power: 11	Hi, It seems that your mesh isn't good enough : 85 max non-orthogonality is quite high. Try to improve your mesh, and it should be better. Regards, Sati

January 18, 2017, 13:56		#3
sheaker Senior Member Oskar Join Date: Nov 2015 Location: Poland Posts: 184 Rep Power: 11	Hello. As sati said, You have high non-orthogonality in Your mesh. Also... Is Your case really 54m^3? Or maybe You forgot to transform units from [mm] to [m]?

January 20, 2017, 04:19		#5
sati New Member Join Date: Mar 2015 Posts: 16 Rep Power: 11	You can indeed improve your mesh with a different blocking. You are using a single block to mesh a cylinder. This is not optimal : the cells situated at the corner of your block are very distorted. To improve that, you can use a blocking similar to the one used in the following picture :

January 20, 2017, 05:20		#6
ali11 New Member Join Date: Sep 2013 Posts: 18 Rep Power: 13	thank you sati! I got your point.