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Time-dependent thermal conductivity

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Dear Matlab community,
I am using the PDE toolbox to solve a transient thermal model. Among thermal properties, thermal conductivity changes over time. I used the function handle:
k = @(~,state) kin-(kin-kfin)/(duration/state.time);
But when I run the code, it prompts that: "Coefficient evaluation function, "@(~,state) kin-(kin-kfin)/(duration/state.time)", was requested to
calculate coefficients at 2500 locations so should have returned a matrix with 2500 columns. Instead it returned a matrix with 1
columns.
How can I solve this issue?
Thank you
  1 Comment
Bjorn Gustavsson
Bjorn Gustavsson on 28 Aug 2019
If your thermal conductivity varies equally over the entire region independently of temperature or spatial coordinate just use repmat of your eqpression to the desired size, or multiply it with ones(size(x)) or whatever spatial coordinate the pde-solver calls your function k with.
HTH

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Accepted Answer

Ravi Kumar
Ravi Kumar on 28 Aug 2019
Function should return values of k at all points requested by the solver, points are in the first argument. Update your funciton to:
k = @(location,state) ones(size(location.x))*kin-(kin-kfin)/(duration/state.time);
  1 Comment
Giulia Ulpiani
Giulia Ulpiani on 29 Aug 2019
Thank you very much. That solved the problem.

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