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IF OPERATOR
Posted Oct 3, 2011, 8:59 a.m. EDT Parameters, Variables, & Functions Version 4.2 1 Reply
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Hi,
I am solving the Helmholtz equation and I would like to use the IF operator such that when the dependent variable u > uref, then I specify the parameter c = 100 and when u < uref, c = 10.
Can I use IF(u>uo,100,10) when specifying the value of c? Because u is also a dependent variable, I am not sure if this is permitted in COMSOL.
To make it more simple, suppose that you are solving a heat transfer equation and you want to specify the thermal conductivity such that when the temperature is less than a certain value, you let the thermal conductivity be A and when it is greater, then the thermal conductivity is B.
Can anyone help with this?
Thanks.
Sincerely,
EH
I am solving the Helmholtz equation and I would like to use the IF operator such that when the dependent variable u > uref, then I specify the parameter c = 100 and when u < uref, c = 10.
Can I use IF(u>uo,100,10) when specifying the value of c? Because u is also a dependent variable, I am not sure if this is permitted in COMSOL.
To make it more simple, suppose that you are solving a heat transfer equation and you want to specify the thermal conductivity such that when the temperature is less than a certain value, you let the thermal conductivity be A and when it is greater, then the thermal conductivity is B.
Can anyone help with this?
Thanks.
Sincerely,
EH
1 Reply Last Post Oct 3, 2011, 9:21 a.m. EDT
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Posted:
1 decade ago
Hi
what happens when the variable is equal the test value ? then how to define a derivative (left/right ?)
using if(u,,) means that depending on the diplacement something happens with your value, as u=u(x,y,z) it might differe when and where it happns, I believe it should work, but you should ensure you have a rather smooth derivable transition, else you might have a serious convergence issue.
You might also get into a circular dependence if you loop your variables in the wrong way, to be checked carefully
--
Good luck
Ivar
what happens when the variable is equal the test value ? then how to define a derivative (left/right ?)
using if(u,,) means that depending on the diplacement something happens with your value, as u=u(x,y,z) it might differe when and where it happns, I believe it should work, but you should ensure you have a rather smooth derivable transition, else you might have a serious convergence issue.
You might also get into a circular dependence if you loop your variables in the wrong way, to be checked carefully
--
Good luck
Ivar