Set these boundary conditions in COMSOL 3.4?

AI Thread Summary
In the discussion about setting boundary conditions in COMSOL 3.4, users seek guidance on implementing specific conditions for a system of PDEs in cylindrical coordinates, particularly under axisymmetric cases. The main boundary conditions discussed include setting u=0 and vr=0, where vr is the derivative of v with respect to r. Suggestions include using Dirichlet, Neumann, or mixed boundary conditions directly from the physics settings or manipulating boundary terms within the equation systems. Additionally, another user inquires about creating photonic crystal fibers and tapered optical fibers in COMSOL 3.5, expressing difficulty in understanding the models and parameters due to a lack of detailed documentation. The conversation highlights the need for clearer resources and examples for complex structures in COMSOL.
sunilpatilher
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Hello friends,
Thanks in advance for your answers,

I am using genreal form of PDE to solve system of PDEs. I am dealing with cyllindrical co-ordinates under axisymmetric case. I am not able to understand how to implement boundary conditions such as,

DEL. Gamma=F is system of PDEs
where Gamma is function of (u, v, ur, uz,vr,vz..)

I would like to set u=0 and vr=0 on one of boundary, vr stands for derivative of v w.r.t. r.

can anyone tell me how to set these boundary conditions in COMSOL 3.4?

Thanks again.
sunil
 
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You can give Dirichlet, Neumann or mixed BCs directly from physics --> boundary (depending on your application mode), or then you can go about it via physics --> equation systems and work with the boundary terms for the PDE you're working with or define something specific for a boundary in question (if you need something more general). If you've something beyond this there are further means, Comsol is fairly general this way.
 
PCFs and COMSOL

Hello everyone, I am trying to understand COMSOL 3.5 and I am interested in Photonic crystal fibres and tapered optical fibres. First of all, could you please tell me what is the background of the layout? When you create a design/object, the rest area is air or I need to define another object as the environment?
Now, could you please tell me where I can find instructions of how creating a PCF structure in COMSOL? Furthermore, do you know any good notes/books for COMSOL for photonic applications??
Thank you in advance

Chris
 


Chris,

Did you check out the models and documentation that comsol provides? They have some examples that once the work through may be helpful. I think it has an optical fiber example in there. That's pretty much how I have taught myself Comsol. I don't know of any good books that are out and I have looked around. Maybe someone else knows of one?

Jacob
 


Dear Jacob,
Thank you for your reply. Of course I have checked the examples and the one with the optical fibre; however an optical fibre is a very simple structure and quite different from a photonic crystal fibre and a tapered fibre (of diameter 1um without cladding). Furthermore, due to fact that these models are ready, I don't really know every parameter used in the model because its default and unfortunately the documentation does not explain in details. Thank you for your reply and your time, though. I hope that someone else is also faced with similar problems and will give an answer.

Best Regards,
Chris
 
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