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wing with sharp trailing edge mesh through extrusion

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Old   February 21, 2013, 13:16
Default wing with sharp trailing edge mesh through extrusion
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Ali
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How can I extrude a wing having sharp trailing edge?

I have come to know that by adding wake domain, the select wing domains and wake domain and extrude all of them at once. By doing so, I get a mesh with wing domains (upper and lower) extruded up and down while wake domain extruded only in one direction.

How can I get the wake domains extruded on both sides?

If one can try, can assume any wing with sharp trailing edge.
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Old   February 24, 2013, 17:25
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John Chawner
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I'm going to attempt an answer without actually trying it myself first. When you define the initial face from which extrusion will begin (clockwise: wake, lower wing, upper wing, wake) you have to select the wake domain twice.
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Old   February 25, 2013, 10:38
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I tried this but I am not able to select a domain twice in Pointwise. You can try using any generic wing with a sharp trailing edge. I wand to use NORMAL extrusion.
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Old   February 25, 2013, 10:50
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That's the danger of me answering without trying it myself. At this point your best bet is to contact our tech support team directly at support@pointwise.com.
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Old   February 25, 2013, 23:34
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Chris Sideroff
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Ali,

The trick to getting this to work is to assemble the face manually. If your mesh, for example, had three domains (one for lower wing, one for upper wing and one for the wake) choose all three and select Create, Extrude, Normal ...

In the Assemble panel, check the Assemble Special box to expand the panel. Now click Delete All Faces to restart the face assembly process and uncheck Domain Once to allow selection of the wake domain more than once. Starting with the wake domain, pick the domains in successive order (e.g. wake, upper surface, lower surface, wake again).

When you select the wake domain again, you will be presented with the linkage assembly diagram and a list of domain-face linkages. You need to choose the linkage at the trailing edge of the airfoil. Click Use Selected Link, click Save Face and click Done. It's important to follow these steps exactly. If you did you should be in the usual Extrusion mode and the extrusion will march off of both sides of the wake domain (you should see arrows pointing from both sides).

Let me know if you get it working, Chris

Quote:
Originally Posted by Hybrid View Post
How can I extrude a wing having sharp trailing edge?

I have come to know that by adding wake domain, the select wing domains and wake domain and extrude all of them at once. By doing so, I get a mesh with wing domains (upper and lower) extruded up and down while wake domain extruded only in one direction.

How can I get the wake domains extruded on both sides?

If one can try, can assume any wing with sharp trailing edge.
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File Type: jpg 3D-airfoil-wake-01.jpg (52.9 KB, 138 views)
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Old   February 26, 2013, 14:39
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Thanks Chris Sideroff. It works really great.

Now a new problem, how to control the quality...extrusion fails after 3,4 steps. Sometime extruded root and tip airfoil connectors deshaped.

How can i get a nice mesh with minimum skewness and orthogonal?

How to check orthogonality in Pointwise?
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Old   February 26, 2013, 19:39
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Chris Sideroff
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Ali,

By default, the normal extrusion only checks for negative Jacobians (aka cells with negative volume). There is additional cell quality checking you can monitor during the extrusion.

Back to your difficulty getting the extrusion to proceed. My first suggestion, and something I always watch for is mis-matched spacings in the domains of the starting face. Using my simple 3D airfoil as an example, I made sure the streamwise spacing at the trailing edge of the wing was the same as the streamwise spacing of the wake domain. This is particularly important when extruding from concave (i.e. internal) corners.

The next suggestion is to keep the initial normal spacing (init ds) about 4-6x smaller than the smallest transverse spacing in the domains of the starting face.

My last suggestion is to turn down the volume smoothing parameter to a small value (e.g. 0.05) until the extrusion proceeds away from the wall at least one BL thickness. Volume smoothing controls how much the algorithm smooths the extrusion front and I find, for tougher extrusions, the default value of 0.5 is too high. You can turn it back up once the extrusion gets away from the wall.

These are my general suggestions. If they still don't work, you're going to have to at least post a picture of your mesh so I can give more specific advice.

-Chris

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Originally Posted by Hybrid View Post
Thanks Chris Sideroff. It works really great.

Now a new problem, how to control the quality...extrusion fails after 3,4 steps. Sometime extruded root and tip airfoil connectors deshaped.

How can i get a nice mesh with minimum skewness and orthogonal?

How to check orthogonality in Pointwise?
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Old   March 3, 2013, 17:07
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Hi Ali,
See my reply to the other message "[Pointwise] Boundary layer mesh" posted recently, hopefully that might also be helpful to you.

good luck.
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Old   March 18, 2013, 17:17
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Ali
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Quote:
Originally Posted by cnsidero View Post
Ali,

The trick to getting this to work is to assemble the face manually. If your mesh, for example, had three domains (one for lower wing, one for upper wing and one for the wake) choose all three and select Create, Extrude, Normal ...

In the Assemble panel, check the Assemble Special box to expand the panel. Now click Delete All Faces to restart the face assembly process and uncheck Domain Once to allow selection of the wake domain more than once. Starting with the wake domain, pick the domains in successive order (e.g. wake, upper surface, lower surface, wake again).

When you select the wake domain again, you will be presented with the linkage assembly diagram and a list of domain-face linkages. You need to choose the linkage at the trailing edge of the airfoil. Click Use Selected Link, click Save Face and click Done. It's important to follow these steps exactly. If you did you should be in the usual Extrusion mode and the extrusion will march off of both sides of the wake domain (you should see arrows pointing from both sides).

Let me know if you get it working, Chris

Thanks All who reply the post.

It works but need more practice and experience on Extrusion especially Normal Extrusion.
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