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Old   December 26, 2009, 06:51
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Hi Everybody,,
In meshing banki water turbin. i have problem in controlling pattern of meshing. I've read that it can be solved by size function. I've tried to apply the step from "gambit tip & trick" but it can't work. Can you help me out my problem?? do you have reference??
thanks
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Old   January 4, 2010, 05:13
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Maxime Perelli
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check User Guide, size functions are well described
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Old   January 4, 2010, 16:00
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i have problems with the size function too. i dont think they are that well explained in the online help for someone who is unexperienced.

i have a simple airfoil and an outerflowfield. i want to create a mesh which is fine near the airfoil and gets bigger at the flowfield borders. what do i need to set as source and attachment?

and what values should i use for start size, growth and size limit.

thanks
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Old   January 4, 2010, 17:28
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Quote:
Originally Posted by -mAx- View Post
check User Guide, size functions are well described
thanks max. I have understood it. But my geometry is complex enough hence i cannot apply size function easily. I have tried to make inflated boundary but it cannot work so i just mesh in high density of mesh around the blade.
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Old   January 4, 2010, 17:33
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Quote:
Originally Posted by dralosdir View Post
i have problems with the size function too. i dont think they are that well explained in the online help for someone who is unexperienced.

i have a simple airfoil and an outerflowfield. i want to create a mesh which is fine near the airfoil and gets bigger at the flowfield borders. what do i need to set as source and attachment?

and what values should i use for start size, growth and size limit.

thanks
Hi
check this out!! www.anova.com.tr/dosyalar/destek/gambittips.pdf
Maybe it can help you out your problem.
By the way, for smooth mesh near wall, why you don't use boundary layer mesh?? i think its great to get drag value!!
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Old   January 5, 2010, 02:22
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for complex geometries, you need to split your domain into several smaller subdomains.
You will have more control on your mesh
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Old   January 5, 2010, 09:54
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thank you for your help.

the thing i am doing is for a schoolproject. we are told to find the cl of an airfoil. we need to create a boundary layer around the airfoil and then us tri/pave for the mesh.

i attached some pictures so that you can see what i mean. the outerflowfield is a face and the innerflowfield is a face too.

if i now use the size function and pick the edges of the airfoil as source and the innerflowfield face as attachment it doesnt quite seem to work. i dont get a mesh at all. maybe someone of you knows some good values i need to enter?

outerflowfield:



innerflowfield:

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Old   January 6, 2010, 02:02
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we can't see the pictures
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Old   January 6, 2010, 12:31
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I can see the pics... Maybe it is because I wear these cool shades
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Old   January 6, 2010, 13:44
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i dont know why max cant see the pictures. maybe you have an adblocker which blocks tinypic?

anyways, i figured out how to use the size function now thanks again for your help.
the next problem i have is that i have a negative volume (i am in 2d though, dont know whats happening) somewhere in my mesh when i read it into fluent.
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Old   January 6, 2010, 20:01
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Quote:
Originally Posted by dralosdir View Post
i dont know why max cant see the pictures. maybe you have an adblocker which blocks tinypic?

anyways, i figured out how to use the size function now thanks again for your help.
the next problem i have is that i have a negative volume (i am in 2d though, dont know whats happening) somewhere in my mesh when i read it into fluent.
You can check the worst element of your mesh and repair it. I think that is the troublemaker of your case.
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Old   January 6, 2010, 20:04
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Quote:
Originally Posted by -mAx- View Post
for complex geometries, you need to split your domain into several smaller subdomains.
You will have more control on your mesh
Thank's max, I'll try that!!!
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Old   January 7, 2010, 01:52
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In Gambit go to examine mesh.
Choose Volume, and set the max value to 0.
It will show you all cells with negative volume
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Old   January 7, 2010, 01:53
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Quote:
Originally Posted by teguhtf View Post
You can check the worst element of your mesh and repair it. I think that is the troublemaker of your case.
teguhtf
i think i have one element with a negative volume and 10 left handed elements. how can i find those?
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