Irregular cells unstructured

n00bie · May 17, 2017, 09:04

Does anyone know, how I can prevent this from happening? (see attached picture)

As I understand it, Pointwise should automatically try to produce cells that gradually become larger, yet whenever I try to create an unstructured mesh, I get results similar to this.

Is there any way to influence the unstructured mesh other than how I place my points along the connectors. Any settings that I need to change? I could not find any options in the Grid menu or anywhere else.

Thank you in advance.

rmatus · May 17, 2017, 09:22

That's an interesting picture. How did you get those two even layers of triangles in there?

The control over how quickly the triangles grow is called Boundary Decay, and you can find it on the Attributes tab in Grid, Solve . It is a value between 0 and 1 with a default of 0.5. 0 causes the cells to grow very rapidly and 1 extends the influence of the boundary spacing farther into the interior.

In this case, it looks like you need to increase the Boundary Decay.

The other control that could affect this is the Max. Equilateral Edge Length, which is in the Cells pane on the same panel. I don't think that is what you want for this case, but it is an option.

This is all described in Section 9.6.2 of the Pointwise User Manual, which you can access directly in Pointwise from the Help menu.

Hope this helps,
Rick

n00bie · May 17, 2017, 11:14

Yes that sounds good I will try that

thank you

Sent from my LG-H870 using CFD Online Forum mobile app

n00bie · May 18, 2017, 07:12

I tried changing the boundary decay,
but it didn't influence the mesh at all...

Are there any other things I could try?

I will also attach a picture without the T-Rex cells,
maybe that makes the origin of the problem clearer.

Is it just a problem with going from a very fine structured mesh
to an unstructured one and can't be avoided?
That would be very frustrating.

I hope there are other options.

rmatus · May 18, 2017, 08:33

Something is forcing much different edge lengths on the interior of the domain than along the edge.

Are you using the default settings in Grid, Solve? Are you specifying a Min. Equilateral Edge Length in the Cells pane of the Grid, Solve, Attributes panel? What is Pointwise reporting as the Actual and User Specified Min. Equilateral Edge Length there?

Would not have guessed those two layers of triangles in your original picture were T-Rex cells. What is your average boundary spacing and what step size are you using?

It might be easier if you could save a Pointwise project file with just this domain (select the domain and then File, Save Selection As...) and share it here.

Thanks,
RIck

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May 17, 2017, 09:22		#2
rmatus Senior Member Rick Matus Join Date: Mar 2009 Location: Fort Worth, Texas, USA Posts: 116 Rep Power: 17	That's an interesting picture. How did you get those two even layers of triangles in there? The control over how quickly the triangles grow is called Boundary Decay, and you can find it on the Attributes tab in Grid, Solve . It is a value between 0 and 1 with a default of 0.5. 0 causes the cells to grow very rapidly and 1 extends the influence of the boundary spacing farther into the interior. In this case, it looks like you need to increase the Boundary Decay. The other control that could affect this is the Max. Equilateral Edge Length, which is in the Cells pane on the same panel. I don't think that is what you want for this case, but it is an option. This is all described in Section 9.6.2 of the Pointwise User Manual, which you can access directly in Pointwise from the Help menu. Hope this helps, Rick

May 17, 2017, 11:14		#3
n00bie New Member Sabrina Join Date: May 2017 Posts: 7 Rep Power: 8	Yes that sounds good I will try that thank you Sent from my LG-H870 using CFD Online Forum mobile app

May 18, 2017, 08:33		#5
rmatus Senior Member Rick Matus Join Date: Mar 2009 Location: Fort Worth, Texas, USA Posts: 116 Rep Power: 17	Something is forcing much different edge lengths on the interior of the domain than along the edge. Are you using the default settings in Grid, Solve? Are you specifying a Min. Equilateral Edge Length in the Cells pane of the Grid, Solve, Attributes panel? What is Pointwise reporting as the Actual and User Specified Min. Equilateral Edge Length there? Would not have guessed those two layers of triangles in your original picture were T-Rex cells. What is your average boundary spacing and what step size are you using? It might be easier if you could save a Pointwise project file with just this domain (select the domain and then File, Save Selection As...) and share it here. Thanks, RIck