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transient analysis problem
Posted 2012年6月15日 GMT-4 01:48 Battery Design, Chemical Reaction Engineering 3 Replies
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Hello, I am trying to do the unsteady analysis of the PEMFC using the method of transient in the solve parameters.
As we know, in the constant option, we can give one value of V_cell, and use the solve parameter to get different V_cell value in order to draw the V-I curve.
But what I want to know is: how to give the changed value of V_cell by time;
such as: when time is one second, V_cell = 0.2V ; when time is two seconds,
V_cell = 0.5V; when time is three seconds, V_cell = 0.8V ......
Is there any methods to do this job?
Thanks for your time!
3 Replies Last Post 2012年6月28日 GMT-4 04:09
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Posted:
1 decade ago
Hi
the crude way is to say V = V0*(t>=0)*(t<1)+V1(t>=1)*(t<2)+ ...
But this makes a stepwise system, its better to use a rect() or step() (combination of Heavyside functions in 3.5) operator with smootheened transition, its often easier for the solvers
--
Good luck
Ivar
the crude way is to say V = V0*(t>=0)*(t<1)+V1(t>=1)*(t<2)+ ...
But this makes a stepwise system, its better to use a rect() or step() (combination of Heavyside functions in 3.5) operator with smootheened transition, its often easier for the solvers
--
Good luck
Ivar
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Posted:
1 decade ago
Thank you for your message !
But, still now I don't solve my problem..
What is stepwise system ?
what is combination of Heavyside functions ?
V = V0*(t>=0)*(t<1)+V1(t>=1)*(t<2)+ ...
this method apply for expression ?
I really don't know how to do..
Can you recommend another method in COMSOL tutorial model?
I try many times to find similer model and commend in COMSOL DOCUMENTATION PDF file..
But I can't find method.
please more specific suggest method .
Best wishes !
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Posted:
1 decade ago
Hi
in V4 you ahve predefined STEP() functions that are smoothed., In 3.5 you need to call the internal Heavyside functions. Index your doc and search for Heavyside, you will find them described, then you need to combine them. You can also search on the forum for 3.5 threads, these functions were often used back in 3.5 time ;)
--
Good luck
Ivar
in V4 you ahve predefined STEP() functions that are smoothed., In 3.5 you need to call the internal Heavyside functions. Index your doc and search for Heavyside, you will find them described, then you need to combine them. You can also search on the forum for 3.5 threads, these functions were often used back in 3.5 time ;)
--
Good luck
Ivar