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Definition of step function in time-harmonic analysis.
Posted 16.02.2011, 01:59 GMT-5 Acoustics & Vibrations Version 3.5a 1 Reply
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Hello,
I am trying to define a step function as boundary condition in time-harmonic analysis. For example, (a(t)>b)*a+(a(t)<b)*b. But since in time-harmonic analysis, any boundary condition can not be a function of time, can any one give me a help about how to deal with this kind of situation?
Thank you very much.
I am trying to define a step function as boundary condition in time-harmonic analysis. For example, (a(t)>b)*a+(a(t)<b)*b. But since in time-harmonic analysis, any boundary condition can not be a function of time, can any one give me a help about how to deal with this kind of situation?
Thank you very much.
1 Reply Last Post 16.02.2011, 02:46 GMT-5
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Posted:
1 decade ago
Hi
boolean step function are nice but the resulting function is not derivable, hence the solver that relies on derivatives for its projections have some issues and often will not converge, you should use Heaviside functions (see the numerous treads on the forum, and the doc) to smoothen your transitions.
Then I agree changing the BC with time means you are changing the modes with the time which means for me that you are imposing some schizophrenic behavior on the time-harmonic solver. I do not expect that will give any reasonable results, standard transient would probably be better for such BC cases
--
Good luck
Ivar
boolean step function are nice but the resulting function is not derivable, hence the solver that relies on derivatives for its projections have some issues and often will not converge, you should use Heaviside functions (see the numerous treads on the forum, and the doc) to smoothen your transitions.
Then I agree changing the BC with time means you are changing the modes with the time which means for me that you are imposing some schizophrenic behavior on the time-harmonic solver. I do not expect that will give any reasonable results, standard transient would probably be better for such BC cases
--
Good luck
Ivar