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How to use the Flux/source BC of with General form PDE?
Posted Nov 16, 2010, 12:37 a.m. EST 2 Replies
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Hi, everyone
I have used the Comsol 4.0 for several months, but the problem confuses me all through. There are two types of BCs in PDE in V4.0. One is Dirichlet BC and the other is Flux/source BC. In General form, the equation of Flux/source BC is -n*Gamma=g, which is always be considered the 2rd BC, i.e. the Neumann BC. But I cannot find any differentiating in the equation.
In 1D problem, the boundarys is two points. So "the flux on a point" means strange! If the flux is electrical flux or magnetic flux, I can understand. But if the flux is generalized in general PDE, I donot know what it represent.
If solving a simple PDE problem "du/dx=2*x" in the interval of x(-[0,1], how to choose the BCs? What do the Flux/source BC means when the boundary is a point?
Thanks for any comment!!
youf.
I have used the Comsol 4.0 for several months, but the problem confuses me all through. There are two types of BCs in PDE in V4.0. One is Dirichlet BC and the other is Flux/source BC. In General form, the equation of Flux/source BC is -n*Gamma=g, which is always be considered the 2rd BC, i.e. the Neumann BC. But I cannot find any differentiating in the equation.
In 1D problem, the boundarys is two points. So "the flux on a point" means strange! If the flux is electrical flux or magnetic flux, I can understand. But if the flux is generalized in general PDE, I donot know what it represent.
If solving a simple PDE problem "du/dx=2*x" in the interval of x(-[0,1], how to choose the BCs? What do the Flux/source BC means when the boundary is a point?
Thanks for any comment!!
youf.
2 Replies Last Post Nov 16, 2010, 8:21 a.m. EST
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Posted:
1 decade ago
Hi
what if you say flux - gradient- slope, does that help
--
Good luck
Ivar
what if you say flux - gradient- slope, does that help
--
Good luck
Ivar
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Posted:
1 decade ago
Hi, Ivar
Thanks for your reply!
Yes, flux can be regarded as "gradient, slope". However, there is not any differentiating operation in the equation of -n*Gamma=g. Then how to comprehend the equation?
Thanks you!
youf.
Thanks for your reply!
Yes, flux can be regarded as "gradient, slope". However, there is not any differentiating operation in the equation of -n*Gamma=g. Then how to comprehend the equation?
Thanks you!
youf.