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Reactions with non-integer exponents
Posted 15 févr. 2017, 06:36 UTC−5 Chemical Reaction Engineering Version 5.1 1 Reply
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I am using the transport of diluted species physics (let's call it species "c") and have stumbled across a problem that is driving me up the wall. I have the diffusion equation being applied to a 3D geometry but there is also a REACTION part to my model, which I added to the physics and gave a reaction rate. Within the reaction rate I am using a non-integer exponent for example: -c^(2/3).
Now, when I do this COMSOL tries to apply this power to negative values and so my question is this: is there a way to tell COMSOL that if it comes across a negative value, to just treat it as zero? I.e if c<0 then make c=0.
I am slowly going mad, help me Obi-Wan Kenobi!
David
Now, when I do this COMSOL tries to apply this power to negative values and so my question is this: is there a way to tell COMSOL that if it comes across a negative value, to just treat it as zero? I.e if c<0 then make c=0.
I am slowly going mad, help me Obi-Wan Kenobi!
David
1 Reply Last Post 16 févr. 2017, 05:43 UTC−5
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Posted:
8 years ago
I suggest that instead of writing c^(2/3), write (max(eps,c))^(2/3). I cannot guarantee that it works 100% but please try.
eps is a machine constant, a very small positive number.
BR
Lasse
eps is a machine constant, a very small positive number.
BR
Lasse