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Changing predefined equations - multiplying by a constant
Posted 10 set 2014, 12:35 GMT-4 Modeling Tools & Definitions, Parameters, Variables, & Functions Version 4.4 1 Reply
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I'm working with the built in equations for Transport of a Diluted species. I just need to multiply the time derivative by a analytic function. Is there a way to do this?
I thought about dividing the Diffusion coefficient by the function but technically it needs to be outside of the differential operator so I don't think this will work.
Any help is appreciated!
I thought about dividing the Diffusion coefficient by the function but technically it needs to be outside of the differential operator so I don't think this will work.
Any help is appreciated!
1 Reply Last Post 12 set 2014, 08:25 GMT-4
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Posted:
10 years ago
Hi,
The equation that the Transport of Diluted Species interface solves does not include a factor in front of the time derivative dc/dt. What you can do is to enable the Equation View from the Show menu at the top of the Model Builder window. You can then edit the equations that the Transport of Diluted Species interface generates in the Equation View subnodes that appear. In the Settings window for the Equation View node under Transport Properties, locate the first row under Weak Expressions, where the equation appears in a weak formulation. You can then add a factor to the -ct*test(c) term, which represents the time derivative. Bear in mind that if you modify the underlying equations, those changes may affect the interpretation of the results.
Best regards,
Magnus Ringh, COMSOL
The equation that the Transport of Diluted Species interface solves does not include a factor in front of the time derivative dc/dt. What you can do is to enable the Equation View from the Show menu at the top of the Model Builder window. You can then edit the equations that the Transport of Diluted Species interface generates in the Equation View subnodes that appear. In the Settings window for the Equation View node under Transport Properties, locate the first row under Weak Expressions, where the equation appears in a weak formulation. You can then add a factor to the -ct*test(c) term, which represents the time derivative. Bear in mind that if you modify the underlying equations, those changes may affect the interpretation of the results.
Best regards,
Magnus Ringh, COMSOL