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artificial diffusion
Posted 2 ott 2010, 09:53 GMT-4 1 Reply
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Hi,
I have a system of PDEs with two variables u1 and u2. I'm using PDE module. I know that I need to add artificial diffusion to both equations to converge. I add -D*u1x and -D*u2x to the flux term. D is artificial diffusion constant.
problem is that from case to case (changing initial state or injection condition) the program converges not for smaller values of D than D0 and this D0 depends on the case.
on the other hand my solution changes a little if I use relatively bigger valu of D than the minimum convergable D. but as I said this minimum varies from case to case.
Is it possible to ask comsol to add minimum convergable artificial diffusion addaptive to each grid block itself rather than I set the fix value of D?
I'm using general PDE module and transient solution in comsole 3.5a.
I really appreciate your help.
Thanks
I have a system of PDEs with two variables u1 and u2. I'm using PDE module. I know that I need to add artificial diffusion to both equations to converge. I add -D*u1x and -D*u2x to the flux term. D is artificial diffusion constant.
problem is that from case to case (changing initial state or injection condition) the program converges not for smaller values of D than D0 and this D0 depends on the case.
on the other hand my solution changes a little if I use relatively bigger valu of D than the minimum convergable D. but as I said this minimum varies from case to case.
Is it possible to ask comsol to add minimum convergable artificial diffusion addaptive to each grid block itself rather than I set the fix value of D?
I'm using general PDE module and transient solution in comsole 3.5a.
I really appreciate your help.
Thanks
1 Reply Last Post 3 ott 2010, 03:26 GMT-4
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Posted:
1 decade ago
Hi
I can only add that normally you should be able to replace any constant value, within the COMSOL fields by an expression, so also an expression changing with time, or with the spatial location. In the worst case you make your problem non-linear and it might have issues to converge correctly,or worse you make a circular reference and then your stuck ;)
--
Good luck
Ivar
I can only add that normally you should be able to replace any constant value, within the COMSOL fields by an expression, so also an expression changing with time, or with the spatial location. In the worst case you make your problem non-linear and it might have issues to converge correctly,or worse you make a circular reference and then your stuck ;)
--
Good luck
Ivar