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-   -   Gambit boundary layer distortion (https://www.cfd-online.com/Forums/fluent/68185-gambit-boundary-layer-distortion.html)

 ghost September 9, 2009 11:41

Gambit boundary layer distortion

Hi, I am trying to create a 2D flow over an airfoil using gambit and fluent.

In gambit, I split the airfoil into 6 edges, and the b/l of 5 edges can be meshed correctly. Only the final edge will have some distortion.

This leads to a slowdown in the computer system, which I assumed is caused by a lot of background calculation due to the distortion.

Attached is a picture of what I meant by distortion.

http://img5.imageshack.us/img5/4237/meshun.th.jpg

I created this 2D airfoil by importing a Solidworks IGES file, which contains a 3D model. After that I removed all faces and volumes, except the edges and vertex of one plane of airfoil. Is this method correct?

 delfel September 9, 2009 14:04

Hi ghost,

That method sounds perfect, but in my experience you almost always need to clean up the geometry in some way after importing it from CAD files. In my experience it's especially true at the trailing edge of airfoils. That mess at the trailing edge would most certainly effect your convergence and accuracy and should be cleaned up manually. I would zoom in and see if there is a blunt edge at the trailing edge and either make it sharp or create additional faces to compensate for it. Also, what does your wake mesh look like?

Cheers,
-sean

 ghost September 9, 2009 21:44

How can I actually do cleanup of the model? sorry, this is my first time using gambit.

The trailing edge is sharp as it consist of a single vertex, connecting the top half and bottom half of the airfoil.

What do you mean by creating additional faces at the T/E?

My wake mesh will be using two big rectangles and meshing them using the 'Mesh Edge' and 'Mesh Face' function, not the create b/l function.

 ivanbuz September 13, 2009 05:06

have you tried using a rounded T/E? that way you may also create b/l for it.

 -mAx- September 14, 2009 01:26

I am not experienced with BL, but what you can try is to split your domain from trailing edge point (the one which gives you trouble) till links extremity from your domain.
Your BL will be projected along the split edge and you won't have this distorsion anymore.
It will also enable your to better solve the wake region

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