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When should we use weak form PDE?

Posted 30 gen 2011, 06:11 GMT-5 Version 4.1 3 Replies

Shu Heng Khor
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For PDE interface, three types of PDE are available: general form, coefficient form, and weak form. From what i read, COMSOL automatically convert all the equation into weak form before solving. How do we decide if general form PDE model or weak form PDE model is suitable for different case? What are the differences between the two model interface?

Thanks in advanced.
3 Replies Last Post 30 gen 2011, 11:30 GMT-5
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 30 gen 2011, 09:04 GMT-5
Hi

that is a loooong story, too long to be answered here on the forum. You can find answers (partial) in the different books proposed on the main web site (the one I prefer are the one of Edberg and Zimmermann), but there are also the excellent books of Francois Axisa and Antunes : Modelling of Mechanical Systems: Fluid-structure Interaction, he has also a good one about "Discrete Systems" and "Structural Elements" and still one in preparation (I hope so;)
Not to forget the v4.1 doc of COMSOL and their advanced courses

In anycase start simple, if your PDE looks like a coefficient one, or a general one, then select the closest, but if you really want to understand what is going, on test out the weak form
--
Good luck
Ivar
Hi that is a loooong story, too long to be answered here on the forum. You can find answers (partial) in the different books proposed on the main web site (the one I prefer are the one of Edberg and Zimmermann), but there are also the excellent books of Francois Axisa and Antunes : Modelling of Mechanical Systems: Fluid-structure Interaction, he has also a good one about "Discrete Systems" and "Structural Elements" and still one in preparation (I hope so;) Not to forget the v4.1 doc of COMSOL and their advanced courses In anycase start simple, if your PDE looks like a coefficient one, or a general one, then select the closest, but if you really want to understand what is going, on test out the weak form -- Good luck Ivar
Shu Heng Khor
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Posted: 1 decade ago 30 gen 2011, 10:16 GMT-5
Thanks for your prompt reply. Am I correct to say, that if i use the general form interface, COMSOL will automatically try to reformulate the equation into the weak form? And when weak form interface is used instead, we are converting the equation into weak form manually, in which we would have more control over the formulation?
Thanks for your prompt reply. Am I correct to say, that if i use the general form interface, COMSOL will automatically try to reformulate the equation into the weak form? And when weak form interface is used instead, we are converting the equation into weak form manually, in which we would have more control over the formulation?
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 30 gen 2011, 11:30 GMT-5
Hi

Yes that is also my understanding

--
Good luck
Ivar
Hi Yes that is also my understanding -- Good luck Ivar

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