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December 16, 2012, 11:50 
how can I apply this BC? please help me

#1 
Senior Member

Hi everybody,
I want to apply this BC to my U: Code:
du/dx=dv/dy , dv/dx=0 any body knows how can I define this BC? any hint will valuable for me. Thank you. 

December 16, 2012, 15:01 

#2 
Senior Member
Ehsan
Join Date: Oct 2012
Location: Iran
Posts: 2,186
Rep Power: 16 
what shape does your boundary have?is it aligned with x or y axis or any other?
Can't you simplify the formula on the boundary? 

December 16, 2012, 15:22 

#3 
Senior Member


December 18, 2012, 07:55 

#4 
Senior Member
ata kamyabi
Join Date: Aug 2009
Location: Kerman
Posts: 322
Rep Power: 8 
Hi
Is your problem 2D? If yes first BC says that div(V)=0 so I think this may be a problematic BC. For the second one I think you can use OF BCs. 

December 18, 2012, 08:23 

#5  
Senior Member

Quote:
These conditions are for only one boundary. I want to apply this two conditions for my boundary simultaneously. yes, I's 2D. the complete form of my bc is attached. thank you. 

December 18, 2012, 09:40 

#6 
New Member
Joe Nick
Join Date: Dec 2012
Posts: 3
Rep Power: 4 
Hello,
without knowing the context of your problem, a good answer will be difficult. Which process do you calculate? What are P, theta, in and out in the attached figure? Have you tried to reformulate the BC using the PDE that is being solved? 

December 18, 2012, 10:26 

#7  
Senior Member

Quote:
Assume a cavity that its right wall is open and the conditions I refered above are the conditions at this open side. my solver is buoyantBoussinesqSimpleFoam and as I mentioned above the pressure is P=0 and the theta is the temperature. What is your meaning of 'reformulation of BC using the PDE that is being solved'? Thank you 

December 18, 2012, 13:12 

#8 
New Member
Joe Nick
Join Date: Dec 2012
Posts: 3
Rep Power: 4 
Hello,
I'm afraid I cannot help, because I don't know this solver. What I mean by reformulating the BC is to make use of the differential equations for U in your solver to simplify your BC. Just a thought. If you explain why you choose this BC instead of showing only the equation, somebody might be able to help. What are you trying to solve conceptually, not mathematically? dv/dx=0 seems to make assumptions about the normal direction of the boundary and can't be applicable in general unless you have some anisotropic forces. 

December 18, 2012, 13:30 

#9 
Senior Member

thank you Joe,
As I mentioned in my last post, I want to model an open cavity. this kind of cavities have an open side that have special conditions that I want to model it. I tried to replace it with other boundary conditions and even with a huge space with special BCs that might make my desired BC. but all of them failed. I will try if can I include this bc in my solver or not!! 

December 24, 2012, 09:10 

#10 
Super Moderator
Bruno Santos
Join Date: Mar 2009
Location: Lisbon, Portugal
Posts: 8,301
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Greetings to all,
Since adambarfi sent me an email the other day about this and although I'm not much of help here, here's what I know on the subject:
Bruno
__________________


December 26, 2012, 14:57 

#11 
Senior Member

thank you Bruno,
I simplified my problem so that my problematic boundary has just one condition: Code:
dv/dx=0 any body knows how can I apply this condition? Thanks 

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