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Dirac Function

Posted Dec 16, 2010, 12:21 p.m. EST 1 Reply

Nathan Toohey
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I need to implement a frequency domain representation of a cosine wave as a scalar expression wave propogation model. This would be a formula an complex expression containing two Dirac delta functions. How would you enter this into COMSOL as a scalar expression? I don't beleive it has a Dirac operator, or does it?

i*pi*[dirac(omega-a)-dirac(omenga+a)]
1 Reply Last Post Dec 16, 2010, 1:29 p.m. EST
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Dec 16, 2010, 1:29 p.m. EST
Hi

the closest you can get to a Dirac function is probably the test() functions, but these apply to dependent variables.
In time series Dirac functions tend to destabilise the solver stepping algorithms, so mostly one should use smoothened functions, but I must admit that I do not really understand what you are doing so I have some difficulties to give you any better clues

--
Good luck
Ivar
Hi the closest you can get to a Dirac function is probably the test() functions, but these apply to dependent variables. In time series Dirac functions tend to destabilise the solver stepping algorithms, so mostly one should use smoothened functions, but I must admit that I do not really understand what you are doing so I have some difficulties to give you any better clues -- Good luck Ivar

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