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-   -   [GAMBIT] boundary conditions in gambit (http://www.cfd-online.com/Forums/ansys-meshing/108543-boundary-conditions-gambit.html)

galapago October 26, 2012 00:02

boundary conditions in gambit
 
hi everybody

i'm trying to simulate a section of a gas turbine blade in fluent with cooling holes and for the geometry, mesh and boundary conditions i use gambit. The solution in fluent present a divergence, i think that some detail in the boundary conditions is wrong, i dont know if all the faces in my geometry must have a boundary condition (wall, interior, etc.) because i let some faces without boundary condition, also i dont know the difference between internal and interior bc. could u help me with these doubts please?

thanks in advance

-mAx- October 26, 2012 13:55

if all your domain is well connected; then you don t need to define interior or internal faces.
Also all the outer surfaces you didn t define will be regrouped as wall boundary.

Now in fluent check if all the boundaries are present in the boundary panel and check if you have some shadow-wall

galapago October 26, 2012 14:06

Max, thanks for your response

then i guiess that a bad connection is the reason for my problems, how could i check the coneectiviti in gambit?
i thinked that are well connected because all the domains sharing faces.

thanks again bro

-mAx- October 26, 2012 14:14

yes you cab check the connectivity of faces here http://202.118.250.111:8080/fluent/G...m#gc_speccolor
Surfaces should appear in pink if surfaces are connected.
Another method for checking, is picking any volume and trying to MOVE it (not copy)
If you can move it; then you have connectivity problem

galapago October 26, 2012 14:23

then maybe isn't connectivity because all my domains appear pinks. aditionally i tried to move all volumes and gambit dont let me. What do u think? is there another way to solve my problem?

-mAx- October 26, 2012 14:29

any wall-shadow in fluent BC-list?
If you stop the diverging solution, you can display the solution.Then display velocity and check if you don t have "wall" which stop the fluid flowing

galapago October 26, 2012 16:20

5 wall shadows.

i can't display velocity but i can display pressure and
nothing interrupt the fluid flowing

-mAx- October 27, 2012 11:56

display and locate wall shadows in fluent; and fix connectivity in gambit

galapago October 28, 2012 00:28

then the solution is fix the zones where wall shadows appear although there is heat transfer in those walls?

-mAx- October 28, 2012 02:59

post some pictures for understanding

galapago October 28, 2012 17:43

Hi Max

100000 thanks for your help

a short description, the fluid enters the channel with a temperature a pressure and the cooling enters the plenum and goes out to cool the blade , then there is heat transfer in the blade, the first picture show the geometry and type zones, the second one show the areas that Fluent wall shadowshttp://i268.photobucket.com/albums/j.../cfdonline.png

http://i268.photobucket.com/albums/j...ner/shadow.png

galapago October 28, 2012 17:51

another doubt

the surfaces around the cooling holes must be wall oe interior? these surfaces belong to a solid and the cooling holes are fluids

-mAx- October 29, 2012 04:06

can you post first picture with shaded mode turned on?

galapago October 29, 2012 14:46

Hi Max

http://i268.photobucket.com/albums/j...ner/shaded.png

-mAx- October 30, 2012 03:37

I am not experienced with solid conduction, I recommend you: http://aerojet.engr.ucdavis.edu/flue...e567.htm#86350

Also I recommend you to simplify your physic and start without solid elements (no solid conduction).
Then when you get congerged solution, increase complexity with solid conduction


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