Note: This discussion is about an older version of the COMSOL Multiphysics® software. The information provided may be out of date.
Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.
Changing predefined equations - multiplying by a constant
Posted 10 sept. 2014, 12:35 UTC−4 Modeling Tools & Definitions, Parameters, Variables, & Functions Version 4.4 1 Reply
Please login with a confirmed email address before reporting spam
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 sept. 2014, 08:25 UTC−4
Please login with a confirmed email address before reporting spam
Posted:
1 decade 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