[GAMBIT] BC's value assignment in Gambit Vs. Fluent (solver)

hadikhayyamian · December 20, 2010, 20:24

Hi all,

I was wondering the difference of assigning boundary conditions in Gambit and doing the tha same job in Fluent again.

For example, when I make my geometry in Gambit, I have to define boundary conditions types (say, I select a face as inlet velocity) then I am asked to put its value (velocity magnitude is asked).
But my problem is that when I finish working with Gambit and have to open the meshed file in Fluent Solver, Again I am asked to put associated values for each Boundary Conditions (While I have earlier assigned them in Gambit).

I would like to know why these input values are asked twice?

It would be greatly appreciated, if u reply!

Regards.

ComputerGuy · December 20, 2010, 21:51

hadikhayyamian,

Are you sure that it's not asking you for the boundary name, rather than the boundary value? Gambit is really just a model/mesh creation tool, and doesn't have any reason to ask for inputs on boundary conditions.

The bottom line is: if you have discovered a way to enter such values in Gambit (again, I don't think there is), just don't. All you should have to do is define the type of boundary and the name. Stick with entering the actually boundary values in Fluent.

ComputerGuy

hadikhayyamian · December 20, 2010, 23:09

ComputerGuy;
Thanks for your Extra Fast reply!

I was convinced with your reply.
but I just wanted to prove u what I was talking about by showing u a document. (It is part of a presentations which is talking about Gambit).
but I could not attach it, since it exceeds maximum size.

Thanks.

-mAx- · December 21, 2010, 04:46

you cannot give any value in the BC panel from Gambit. (I am interested by your document)
PS: Gambit doesn t provide any unity with your geometry. You have to scale it in the solver.
So giving values to your BC doesn't make sense, since you would have to modify them again in the solver.

PSYMN · December 21, 2010, 10:25

Yes, I actually talked to some developer types about this a few years ago... I was told that The msh format can hold the boco type, such as INLET, but it doesn't even have a place to put the actual value, such as 10 m/s. I am pretty sure your document is wrong or perhaps mis-interpreted, but I am also interested in seeing it if you could post it somewhere and give us a link.

Usually, I create the boco types, such as Inlet, outlet, symmetry, etc. while I am in the mesher. This way, I am confident that I have all the types while it is still easy to create more if I want. Then I go to Fluent and quickly assign the values. If you get to fluent and don't have a boundary name, it is a hassle to separate one out there.

But, as long as you have the boundary names, you could also just assign both the types and the values in Fluent if you prefer.

hadikhayyamian · December 21, 2010, 13:28

Thanks guys for your answers;

My problem is now resolved, but if u are intrested in that document, I can mail to your Email.

Thanks again.

December 20, 2010, 20:24	BC's value assignment in Gambit Vs. Fluent (solver)	#1
hadikhayyamian Member Khayyamian Join Date: Dec 2010 Posts: 46 Rep Power: 15	Hi all, I was wondering the difference of assigning boundary conditions in Gambit and doing the tha same job in Fluent again. For example, when I make my geometry in Gambit, I have to define boundary conditions types (say, I select a face as inlet velocity) then I am asked to put its value (velocity magnitude is asked). But my problem is that when I finish working with Gambit and have to open the meshed file in Fluent Solver, Again I am asked to put associated values for each Boundary Conditions (While I have earlier assigned them in Gambit). I would like to know why these input values are asked twice? It would be greatly appreciated, if u reply! Regards.

December 21, 2010, 04:46		#4
-mAx- Super Moderator Maxime Perelli Join Date: Mar 2009 Location: Switzerland Posts: 3,297 Rep Power: 41	you cannot give any value in the BC panel from Gambit. (I am interested by your document) PS: Gambit doesn t provide any unity with your geometry. You have to scale it in the solver. So giving values to your BC doesn't make sense, since you would have to modify them again in the solver. __________________ In memory of my friend Hervé: CFD engineer & freerider

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December 20, 2010, 21:51		#2
ComputerGuy Senior Member Real Name :) Join Date: Jan 2010 Location: United States Posts: 192 Rep Power: 16	hadikhayyamian, Are you sure that it's not asking you for the boundary name, rather than the boundary value? Gambit is really just a model/mesh creation tool, and doesn't have any reason to ask for inputs on boundary conditions. The bottom line is: if you have discovered a way to enter such values in Gambit (again, I don't think there is), just don't. All you should have to do is define the type of boundary and the name. Stick with entering the actually boundary values in Fluent. ComputerGuy

December 20, 2010, 23:09		#3
hadikhayyamian Member Khayyamian Join Date: Dec 2010 Posts: 46 Rep Power: 15	ComputerGuy; Thanks for your Extra Fast reply! I was convinced with your reply. but I just wanted to prove u what I was talking about by showing u a document. (It is part of a presentations which is talking about Gambit). but I could not attach it, since it exceeds maximum size. Thanks.

December 21, 2010, 10:25		#5
PSYMN Senior Member Simon Pereira Join Date: Mar 2009 Location: Ann Arbor, MI Posts: 2,663 Blog Entries: 1 Rep Power: 47	Yes, I actually talked to some developer types about this a few years ago... I was told that The msh format can hold the boco type, such as INLET, but it doesn't even have a place to put the actual value, such as 10 m/s. I am pretty sure your document is wrong or perhaps mis-interpreted, but I am also interested in seeing it if you could post it somewhere and give us a link. Usually, I create the boco types, such as Inlet, outlet, symmetry, etc. while I am in the mesher. This way, I am confident that I have all the types while it is still easy to create more if I want. Then I go to Fluent and quickly assign the values. If you get to fluent and don't have a boundary name, it is a hassle to separate one out there. But, as long as you have the boundary names, you could also just assign both the types and the values in Fluent if you prefer.

December 21, 2010, 13:28		#6
hadikhayyamian Member Khayyamian Join Date: Dec 2010 Posts: 46 Rep Power: 15	Thanks guys for your answers; My problem is now resolved, but if u are intrested in that document, I can mail to your Email. Thanks again.