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-   -   Normal Extrusion of unstructured domains (http://www.cfd-online.com/Forums/pointwise/115419-normal-extrusion-unstructured-domains.html)

Hybrid March 30, 2013 11:30

Normal Extrusion of unstructured domains
 
1 Attachment(s)
Hi,

I have tried to extrude --> normal unstructured domains, it looks like as shown in attached pic. There are some kinks, how they can be removed because they create problems for outer block skewness?

In attached image only inner extruded block is shown.


One thing more how to check orthogonal quality of blocks in Pointwise.

cnsidero April 2, 2013 08:45

In general, you can't remove them. They're a result of the extrusion algorithm. Honestly, the wiggles don't look that bad (at least the portion in your picture). They usually get more pronounced they further the extrusion, so you might consider extruding one less layer and there may be less wiggles in it.

There are more advanced parameters you could modify that may (or may not) help. You can enable Triangle Aspect under Smoothing (this should help with the wiggles). If you don't like what Triangle Aspect does, you may consider increasing the number of Step Size and Direction iterations. I've never seen much change by modifying these but it's worth a shot.

What do you do you mean by "orthogonal quality"? If the orthogonal you're referring to is OpenFOAM's, there is no equivalent metric in Pointwise.

Quote:

Originally Posted by Hybrid (Post 417332)
Hi,

I have tried to extrude --> normal unstructured domains, it looks like as shown in attached pic. There are some kinks, how they can be removed because they create problems for outer block skewness?

In attached image only inner extruded block is shown.


One thing more how to check orthogonal quality of blocks in Pointwise.


Hybrid April 2, 2013 14:23

I am referring to Fluent. Fluent always checks orthogonal quality.

cnsidero April 2, 2013 18:25

I was testing out the different parameters in the prism extrusion and found out that turning off the Orthonormal smoothing parameter will pretty much eliminate the wiggles in the extrusion front.

So leave all other parameters default and uncheck Orthonormal smoothing.

Fluent's orthogonal quality metric is pretty much the same as OpenFOAM's meaning there is no quality metric in Pointwise that corresponds to it.

-Chris

Quote:

Originally Posted by Hybrid (Post 417904)
I am referring to Fluent. Fluent always checks orthogonal quality.


nikolaous April 3, 2013 03:25

In fluent use mesh-> info -> quality then mesh-> smooth/swap if repair needed.

Hybrid April 3, 2013 09:37

Quote:

Originally Posted by cnsidero (Post 417936)
I was testing out the different parameters in the prism extrusion and found out that turning off the Orthonormal smoothing parameter will pretty much eliminate the wiggles in the extrusion front.

So leave all other parameters default and uncheck Orthonormal smoothing.

Fluent's orthogonal quality metric is pretty much the same as OpenFOAM's meaning there is no quality metric in Pointwise that corresponds to it.

-Chris

By unchecking Orthonormal smoothing, mrsh quality is poor (skewness angle > 0.98) whereas keeping the default smoothing setting and turning on Triangle aspect serves the purpose with high quality mesh (e.g. skewness = 0.7).

So, I concluded:
Check/Uncheck: Feature
Check: Orthonormal smoothing
Check: Triangle Aspect

jchawner April 8, 2013 09:56

There isn't an explicit orthogonality check except for right at the wall. Otherwise you can use either Equi-volume or Equi-angle skewness (these are very similar to Fluent's measures) or minimum/maximum included angles.


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