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Problem using a function dependent on temperature for subdomain properties

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Hi all!
I'm solving an induction heating problem; using transient analysis for the Thermal part and time-harmonic for the electromagnetics.

I've added a conductivity dependance with temperature without problems, through an analytical function, let's say:
conductivity(T/T0), where T0 is a reference temperature for passing a dimensionless variable (as I've read elsewhere that was mandatory).

Then, I wanted to add permeability dependance, but the problem is that I have experimental data that it's not fittable by any reasonable function; so I used the interpolation option, and in the subdomain's settings I used for the mu_r: mu_T(T/T0)
Where again, mu_T is the function I defined, T is intended to be the temperature and T0 is a reference temperature.

I tried changing the values in the data table of the function (even making it constant), I tried changing the interpolation method (from splines to piecewise cubic, but I'm always getting this error:

Error:
Time 2:
Error in residual computation.
Complex_interpolation_point_found
Function: mu_T
Failed_to_evaluate_variable
Variable: mur_emqap, Defined_as: mu_T((T/T0))
Failed_to_evaluate_variable
Variable: Hz_emqap, Defined_as: (Bz_emqap/(mur_emqap*mu0_emqap))
Failed_to_evaluate_expression
Expression: conj(Hz_emqap)
Failed_to_evaluate_expression
Expression: real((conj(Hz_emqap)*(Bz_emqap*(omega_emqap*(0.5*j)))))
Failed_to_evaluate_variable
Variable: Qmav_emqap, Defined_as: real((conj(Hz_emqap)*(Bz_emqap*(omega_emqap*(0.5*j)))))
Failed_to_evaluate_variable
Variable: Q_ht, Defined_as: (Qmav_emqap+Qav_emqap)
Failed_to_evaluate_expression
Expression: d(((-k_ht*Tx*test(Tx)-k_ht*Ty*test(Ty)+Q_ht*test(T))-(Dts_ht*rho_ht*C_ht*Tt*test(T)))*(dvol),{test@2})
Last time step is not converged.

It's strange buy if I change the function to an analytical one, it works OK. So I'm guessing the problem depends only on the interpolation process but I don't know how to solve it.
Thanks!

0 Replies Last Post Jul 28, 2011, 1:18 p.m. EDT
COMSOL Moderator

Hello Aquiles Carattino

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