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[TGrid] PRISM layer

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Old   February 17, 2010, 10:49
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Hi,
I've a problem generating the prism-layer with Tgrid over a 3D wing: the cell-skewness on the trailing edge is very high (more than 0.99).
Who can I solve this problem? which settings do you advise me?
Thanks
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Old   February 18, 2010, 00:28
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hi sarav

Make sure your surface mesh quality is around 0.6 to 0.65 skewness.
And then try to generate prism layers.

Uday
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Old   February 18, 2010, 03:55
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Hi!
It's impossible for me to obtain max 0.65 for surface skewness because wing trailing edge is very very peaked...
Do you think I will have convergence problems if I try to solve the case with similar volume-cells skewness?
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Old   February 18, 2010, 04:39
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Hi sarav

Yes certainly as your flow will be compressible flow. And flow over the wing are transonic kind of flows.

uday
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Old   February 18, 2010, 05:37
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Hi!
I checked the surface mesh, cells on the trailing edge have skewness less than 0.6. Which could be my problem so?
thanks!
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Old   February 18, 2010, 06:35
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Hi sarav
Check the worst elements those are in the prism by display cells quality.
Prior doing it it plot a histogram of cell skewness between 0.9 to 1 with 10 equal parts.

And then i would like to know how are you managing the trailing edge prism nodes.

In other words the the prisms traveling from pr. side and suction side meet at the trailing edge how are you modeling the prisms there.

Uday
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Old   February 18, 2010, 07:21
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Hi uday.
Well I've done the plots.
I find in the fluid zone only one cell over 0.99. Instead in prism-cells I find zero cell over 0.97. I set the two plots as attachments.

I'm managing the prism over the trailing edge as the rest of the wing...that is to say, for example in my last try, with 10 layers with linear growth of 0.1 of slope and first height of 0.5.

Can I menage the prism in a particular way only on the edge?

thanks

sarav

Last edited by sarav; February 21, 2010 at 05:36.
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Old   February 18, 2010, 07:36
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Hi sarav send me your mesh file

My mail id is udayrg@gmail.com

I will look into it and suggest you and to some extend try to finish the meshing may be upto prisms.

Uday
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Old   February 18, 2010, 08:06
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Hy uday,
sorry but I can't send you the geometry.
I set as attachment a view of the problematic cells, hoping that you could understand the problem from this view.
thanks
sarav
Attached Images
File Type: jpg problematic.JPG (56.6 KB, 57 views)
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Old   February 18, 2010, 08:28
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Okay sarav

1)Refine the surface mesh at the trailing edge region before prism generation
2)I would suggest to put a very small surface at the trailing edge instead of edge. i.e. a very negligible width plane surface and mesh it minimum one element. And then you wont be having any problems generating prism layers on it.


I am afraid that the solution (1) alone. It not difficult however you will have to try number of times with grid refinement at the trailing edge. and You can play with shrinkage option for prism layers.

Uday
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Old   February 18, 2010, 09:28
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Ok I try to refine the surface mesh, and eventually I will modify the geometry in future...
For shrinkage options do you mean "keep first layer offset", gap factor and so on?
thanks again, you are very kind!
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Old   March 3, 2010, 17:24
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Try "minimum height" growth method instead of "uniform"

Use Mesh -> Tools -> Auto node move after creating the prisms to locally smooth bad cells.
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Old   September 9, 2010, 10:57
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Even i am facing same problem while generating prisms & my surface skewness is 0.64 (max). What els can be done to reduce the skewness?? I am using the last ratio method in growth options.
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