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Time derivative of a scalar expression?
Posted Oct 27, 2009, 4:12 p.m. EDT 3 Replies
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Hi
I am trying to calculate the time derivative of a variable that is defined in the scalar expression. I have the box "include time derivatives" checked under "output" tab in solver manager and it does give me all the time derivatives of the primitive variables but doesn't work for the variable under scalar expression. Can anyone please help me with this? Thanks.
-Gunjan.
I am trying to calculate the time derivative of a variable that is defined in the scalar expression. I have the box "include time derivatives" checked under "output" tab in solver manager and it does give me all the time derivatives of the primitive variables but doesn't work for the variable under scalar expression. Can anyone please help me with this? Thanks.
-Gunjan.
3 Replies Last Post Nov 10, 2009, 1:55 p.m. EST
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Posted:
2 decades ago
Hi
I have not understood that COMSOL would provide you internally with time derivatives for other than the usual variables, I expect that you must make your time derivative yourself for "user" variables by manipulating the time sequence
but if you find another way, and if you have a nice piece of code, pls post it here so we coul all learn
Good luck
Ivar
I have not understood that COMSOL would provide you internally with time derivatives for other than the usual variables, I expect that you must make your time derivative yourself for "user" variables by manipulating the time sequence
but if you find another way, and if you have a nice piece of code, pls post it here so we coul all learn
Good luck
Ivar
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Posted:
2 decades ago
Dear Gunjan,
maybe you can set your variable as part of a global equation (see Physics/Global equations) and then solve your problem togheter with the global equation.
Comsol manuals contain a lot of examples about the use of global equations.
I hope this help.
Alessandro
maybe you can set your variable as part of a global equation (see Physics/Global equations) and then solve your problem togheter with the global equation.
Comsol manuals contain a lot of examples about the use of global equations.
I hope this help.
Alessandro
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Posted:
2 decades ago
I tried few different things including the global equation section but no luck so far. So temporarily I am using the analytical solution of the time derivatives until I can come up with something different. It's working but still having some minor troubles. Will keep posted. Thanks a lot for your comments and ideas.
-G
-G