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Boundary condition & Periodic Boundary condition
Posted Nov 27, 2009, 6:55 p.m. EST 3 Replies
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Hi, I using PDE Coefficient ( Transient)mode to solve coupled nolinear PDEs. I need to give the one of the bounday condition as value of the variable. Eg T=300. If I use Dirichlet BC, is it right to specify h= 300?
Another Question
I need to change this BC, at regular intervels. Eg when t=0, T=300 & when t=50 , T=360 & when t =100, T=300 and so on. I hope I can do it with periodic BC.In this case what should i give as ' Exprssion', 'Constraint name','Source','Destination'.?
Your reply highly apprecaited
Thank you
Ramadas
Another Question
I need to change this BC, at regular intervels. Eg when t=0, T=300 & when t=50 , T=360 & when t =100, T=300 and so on. I hope I can do it with periodic BC.In this case what should i give as ' Exprssion', 'Constraint name','Source','Destination'.?
Your reply highly apprecaited
Thank you
Ramadas
3 Replies Last Post Nov 29, 2009, 10:50 p.m. EST
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Posted:
1 decade ago
Hi
I'm not sure to have catched all, but for me if you have a time depending function you can use bolean functions to make piecevise Boundary condition variables
T=T1*(t<1)+T2*(t>=1)*(t<5) ...
to make the transitions smoother and derivable, use rather heaviside functions, you will find them in the Comsol documentation
You can also make global functions and apply them, then at least you should assure that they have defined derivatives
Good luck
Ivar
I'm not sure to have catched all, but for me if you have a time depending function you can use bolean functions to make piecevise Boundary condition variables
T=T1*(t<1)+T2*(t>=1)*(t<5) ...
to make the transitions smoother and derivable, use rather heaviside functions, you will find them in the Comsol documentation
You can also make global functions and apply them, then at least you should assure that they have defined derivatives
Good luck
Ivar
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Posted:
1 decade ago
Hi Ivar,
Attached herewith is the model file.
Here 4 variables are there. At present I am using a single BC and trying to solve. Once it is succesful, I need to use a periodic BC.
First about the present model. I need to put left boundary condition like this: Yg=0.0195 and Tg=300K. All other BC are adiabatic & impermiable ie insulated.So is it right to set BC as Dirichlit and specifying h=0.0195 & h=300 in the respective boxes as done in the file? Is this right?
Is correct to put all other BCs are Neumann to define as insulated.?( I mean no variation with x)?
Once this is done, I need to try for periodic BC. This problem I am trying to solve for the period t= 0 to 100. For the period 0-50, BC1(Yg=0.0195 and Tg=300K) to be applied and for period 50-100,BC2(Yg=0.008 and Tg=360K) to be applied. How is this to be done?
Thanks a lot
Regards
Ramadas
Attached herewith is the model file.
Here 4 variables are there. At present I am using a single BC and trying to solve. Once it is succesful, I need to use a periodic BC.
First about the present model. I need to put left boundary condition like this: Yg=0.0195 and Tg=300K. All other BC are adiabatic & impermiable ie insulated.So is it right to set BC as Dirichlit and specifying h=0.0195 & h=300 in the respective boxes as done in the file? Is this right?
Is correct to put all other BCs are Neumann to define as insulated.?( I mean no variation with x)?
Once this is done, I need to try for periodic BC. This problem I am trying to solve for the period t= 0 to 100. For the period 0-50, BC1(Yg=0.0195 and Tg=300K) to be applied and for period 50-100,BC2(Yg=0.008 and Tg=360K) to be applied. How is this to be done?
Thanks a lot
Regards
Ramadas
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Posted:
1 decade ago
Hi Niklas/ Ivar
Can anyone answer this ?
Your reply well appreciated
Regards
Ramadas
Can anyone answer this ?
Your reply well appreciated
Regards
Ramadas