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-   -   Growth rate control in unstructured blocks (http://www.cfd-online.com/Forums/pointwise/125896-growth-rate-control-unstructured-blocks.html)

Hybrid November 3, 2013 09:25

Growth rate control in unstructured blocks
 
Hi,

How can the growth rate be controlled in unstructured blocks? Near the wall cells are small and immediately cell size becomes larger. I need a smooth transition but keeping the mesh size low.

cnsidero November 3, 2013 21:12

Quote:

Originally Posted by Hybrid (Post 460345)
Hi,

How can the growth rate be controlled in unstructured blocks? Near the wall cells are small and immediately cell size becomes larger. I need a smooth transition but keeping the mesh size low.

Increase the boundary decay in the solver attributes. I typically use somewhere in the range of 0.85 - 0.95.

If you want more explicit size control you can cap the element sizes with min and max edge lengths in the same panel as above.

If that's still not getting you what you want, create a nested block and use the domains at the block interface to better control the rate at which the elements grow.

-Chris

Hybrid November 4, 2013 13:19

Geometry Import problem
 
I have problem with geometry import in Pointwise v17.1 R2. I made the model in SpaceClaim, when I tried to import in Pointwise, the rounded surfaces missed, making sharp edges.

How can I solve this problem?

cnsidero November 4, 2013 16:04

Quote:

Originally Posted by Hybrid (Post 460503)
I have problem with geometry import in Pointwise v17.1 R2. I made the model in SpaceClaim, when I tried to import in Pointwise, the rounded surfaces missed, making sharp edges.

How can I solve this problem?

OK this is a different problem so you should have opened a new thread. Anyway do so next time. I will answer you question here.

Two main questions:

1) What format did you export from SpaceClaim?
2) What is the approximate bounding box size of the geometry? That is if you drew a box that contained all of the geometry, what would the length of the boxes diagonal be (roughly)?

-Chris

Hybrid November 5, 2013 05:39

Quote:

Originally Posted by cnsidero (Post 460521)
OK this is a different problem so you should have opened a new thread. Anyway do so next time. I will answer you question here.

Two main questions:

1) What format did you export from SpaceClaim?
2) What is the approximate bounding box size of the geometry? That is if you drew a box that contained all of the geometry, what would the length of the boxes diagonal be (roughly)?

-Chris

1)- I tried a number of formats like STEP, IGES, Parasolid.
2)- L = 2000mm and H=W=150mm, diagonal = 2005mm

cnsidero November 5, 2013 09:40

Quote:

Originally Posted by Hybrid (Post 460596)
1)- I tried a number of formats like STEP, IGES, Parasolid.
2)- L = 2000mm and H=W=150mm, diagonal = 2005mm

When you import, the IGES for example, what does the Total Grid/DB Length report at the top of the File > Properties panel in Pointwise?

Hybrid November 6, 2013 03:28

Quote:

Originally Posted by cnsidero (Post 460640)
When you import, the IGES for example, what does the Total Grid/DB Length report at the top of the File > Properties panel in Pointwise?

The Total Grid/DB Length is almost twice the L=2000 (Enabaled and Visible Grid/DB Length).

What is the significance of Total Grid/DB Length?

cnsidero November 6, 2013 08:25

Quote:

Originally Posted by Hybrid (Post 460783)
The Total Grid/DB Length is almost twice the L=2000 (Enabaled and Visible Grid/DB Length).

What is the significance of Total Grid/DB Length?

That value should be close to (within a factor of 10 is a good guideline) the Model Size parameter in the same panel. It's default is 1000 so you should be fine. Like any numerical software, the geometry kernel in Pointwise has a fixed floating point range so the Model Size is used to adjust it's internal tolerances to ensure optimal accuracy.

Are there any controls in SpaceClaim for tolerances, etc for export? I've have never used SpaceClaim before so you'll have to help me here.

We're getting to the point where a picture or the geometry would help. Can you post either or both?

dgarlisch November 6, 2013 12:22

If you could attach a CAD file that exhibits the problem, I can examine it more closely. If you are able, please also submit the file to PW support so we can track the resolution of this issue.

Hybrid November 6, 2013 13:22

Quote:

Originally Posted by cnsidero (Post 460834)

We're getting to the point where a picture or the geometry would help. Can you post either or both?

I will let you know about the SpaceClaim tolerance in detail tomorrow. As for as the geometry is concerned, it is not feasible/possible to post here but I can post a picture of it.

I will try to post the CAD privately if you feel comfortable with that.

cnsidero November 6, 2013 21:44

Quote:

Originally Posted by Hybrid (Post 460880)
I will let you know about the SpaceClaim tolerance in detail tomorrow. As for as the geometry is concerned, it is not feasible/possible to post here but I can post a picture of it.

That will help.

Quote:

I will try to post the CAD privately if you feel comfortable with that.
If you're comfortable with that send me a PM.

Hybrid November 7, 2013 07:17

Here is the pictures of geometry:

https://www.dropbox.com/s/8y956mi1p9himar/geom.pdf

cnsidero November 7, 2013 14:18

Quote:

Originally Posted by Hybrid (Post 460986)
Here is the pictures of geometry:

https://www.dropbox.com/s/8y956mi1p9himar/geom.pdf

That helps a ton. Two things. First, it's possible the "defect" you're seeing in the small rounded surface is purely visual and not actual. To test this hypothesis, select those surfaces (or quilts), View>Attributes, check Advanced panel. Increase the triangle density to at least 100 or even 200 and click Apply. If you see the roundedness appear now it was just visual.

The triangle density controls how many triangles are used to render the surface. Even though the surface is mathematically defined (NURBS), to display the surface on the screen using OpenGL there has to be triangular representation of it.

Second, in the SpaceClaim IGES export options choose Manifold B-Rep Solid. Pointwise will recognize this entity type - the solid model - and you will likely save a lot of time by avoiding reassembly of the solid by saving it in the IGES file.

Hybrid November 8, 2013 09:00

Quote:

Originally Posted by cnsidero (Post 461050)
That helps a ton. Two things. First, it's possible the "defect" you're seeing in the small rounded surface is purely visual and not actual. To test this hypothesis, select those surfaces (or quilts), View>Attributes, check Advanced panel. Increase the triangle density to at least 100 or even 200 and click Apply. If you see the roundedness appear now it was just visual.

The triangle density controls how many triangles are used to render the surface. Even though the surface is mathematically defined (NURBS), to display the surface on the screen using OpenGL there has to be triangular representation of it.

The rounded surface is not a visual effect, I tried your suggestion by increasing triangle density is useless.

Quote:

Originally Posted by cnsidero (Post 461050)
Second, in the SpaceClaim IGES export options choose Manifold B-Rep Solid. Pointwise will recognize this entity type - the solid model - and you will likely save a lot of time by avoiding reassembly of the solid by saving it in the IGES file.

It works fine with IGES.

cnsidero November 8, 2013 12:42

Quote:

Originally Posted by Hybrid (Post 461193)
It works fine with IGES.

Does that mean the rounded surfaces are appearing as they should? Just want to make sure your issue is resolved.


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