blockMesh generates under determinants cell

fluxent · February 23, 2017, 13:07

Hello everyone,

I'm trying to simulate an external incompressible flow but the blockMeshDict in attached generates thousands of under determinant cells.

Someone can resolve this issue?

thank you in advance

Andrea

Saideep · February 24, 2017, 12:23

it is extremely difficult to point where the error comes from. Can you attach a figure of what your trying to model?

fluxent · February 25, 2017, 15:29

Quote:

Originally Posted by Saideep

it is extremely difficult to point where the error comes from. Can you attach a figure of what your trying to model?

Hi Saideep,

thank you for your reply,

I'm trying to simulate a flow around a magnetometer in order to evaluate it's drag.

It's an incompressible turbulent steadystate simulation and I'm using simpleFoam but during SHM's quality evaluation I saw that the under determinant cells number was every time constant, so I tryed a checkmesh (all topology -all geometry) immediately after Blockmesh and I noted that the problem was due to blockMesh.

I don't know why blockMesh generates so many under determinant cells, any idea?

thank you

fluxent · February 27, 2017, 13:17

someone who can help me?

KateEisenhower · February 28, 2017, 04:20

Hello fluxent,

I am not very familiar with blockMesh. Can you share a picture of your mesh with the bad cells highlighted for example in paraView.

Best regards,

Kate

fluxent · February 28, 2017, 05:55

Quote:

Originally Posted by KateEisenhower

Hello fluxent,

I am not very familiar with blockMesh. Can you share a picture of your mesh with the bad cells highlighted for example in paraView.

Best regards,

Kate

Hello kate,

I tried to highlight those cells with paraview but no one of them was visible, like if they don't exist.

Flux

KateEisenhower · February 28, 2017, 06:05

You tried with

Code:

foamToVTK -cellSet underdeterminedCells

?

fluxent · February 28, 2017, 06:41

Yes but no result

KateEisenhower · February 28, 2017, 09:02

Do you get the corresponding underdeterminedCells file in the postProcessing folder after executing the command?
If not, do you get a error message?

Antimony · February 28, 2017, 21:09

Hi,

Have you tried running your simulation and see if it runs without diverging? While underdeterminedCells might crop up, it doesn't necessarily mean that it will interfere with your simulation run/results.

Cheers,
Antimony

fluxent · March 3, 2017, 17:08

Quote:

Originally Posted by Antimony

Hi,

Have you tried running your simulation and see if it runs without diverging? While underdeterminedCells might crop up, it doesn't necessarily mean that it will interfere with your simulation run/results.

Cheers,
Antimony

Hi Antimony,

I follow yours suggestion, the simulation converge, but the reason for why blockmesh generates those underdeterminant cells remains unknown.

kind regards

Antimony · March 5, 2017, 22:58

Hi,

I took a look at your blockMeshDict and noticed that the grading ratios that you had, among others, were 0.01 and 100. So it is quite possible in your mesh that there are regions which have extremely small cells and regions were there are large cells leading to underdetermined cells.

Cheers,
Antimony

fluxent · March 10, 2017, 04:15

Thank you antimony I will try as soon as possible then write the results here.
Kind regards

February 24, 2017, 12:23		#2
Saideep Senior Member Saideep Join Date: Apr 2015 Location: INDIA Posts: 203 Rep Power: 12	it is extremely difficult to point where the error comes from. Can you attach a figure of what your trying to model? fluxent likes this.

February 28, 2017, 06:05		#7
KateEisenhower Senior Member Join Date: Mar 2015 Posts: 250 Rep Power: 12	You tried with Code: foamToVTK -cellSet underdeterminedCells ?

February 28, 2017, 21:09		#10
Antimony Senior Member Join Date: Aug 2013 Posts: 407 Rep Power: 16	Hi, Have you tried running your simulation and see if it runs without diverging? While underdeterminedCells might crop up, it doesn't necessarily mean that it will interfere with your simulation run/results. Cheers, Antimony fluxent likes this.

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February 27, 2017, 13:17		#4
fluxent New Member Join Date: Aug 2014 Location: ITALY Posts: 8 Rep Power: 12	someone who can help me?

February 28, 2017, 04:20		#5
KateEisenhower Senior Member Join Date: Mar 2015 Posts: 250 Rep Power: 12	Hello fluxent, I am not very familiar with blockMesh. Can you share a picture of your mesh with the bad cells highlighted for example in paraView. Best regards, Kate

February 28, 2017, 06:41		#8
fluxent New Member Join Date: Aug 2014 Location: ITALY Posts: 8 Rep Power: 12	Yes but no result

February 28, 2017, 09:02		#9
KateEisenhower Senior Member Join Date: Mar 2015 Posts: 250 Rep Power: 12	Do you get the corresponding underdeterminedCells file in the postProcessing folder after executing the command? If not, do you get a error message?

March 5, 2017, 22:58		#12
Antimony Senior Member Join Date: Aug 2013 Posts: 407 Rep Power: 16	Hi, I took a look at your blockMeshDict and noticed that the grading ratios that you had, among others, were 0.01 and 100. So it is quite possible in your mesh that there are regions which have extremely small cells and regions were there are large cells leading to underdetermined cells. Cheers, Antimony

March 10, 2017, 04:15		#13
fluxent New Member Join Date: Aug 2014 Location: ITALY Posts: 8 Rep Power: 12	Thank you antimony I will try as soon as possible then write the results here. Kind regards