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Irregular Time Stepping
Posted Mar 3, 2020, 10:24 a.m. EST Electromagnetic Heating, Mesh, Studies & Solvers Version 5.5 1 Reply
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I am currently modeling the induction heating of a low carbon billet at 40kHz, over a time of 200 seconds. I am having some trouble with the solver, which is unstable and is outputting values at erratic time steps of the form 0.0001 s and so on.
At first I thought it was the mesh of my model and I know based on induction theory that the higher the frequency, the more of the heating is located at the surface. With this in mind, I increased the mesh to be finer and added boundary layers to the billet to capture this. Despite doing this, the solver still remains unstable and the simulation now takes longer to run due to the finer mesh.
I also tried to ramp the input current using a step function to improve the intial conditions of the model but again the solver remains unstable.
I'm kind of stumped as to what could be causing the solver instability and any help would be most appreciated.
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COMSOL takes whatever time steps it needs to converge.
The time steps it RETURNS depend on your choices under Solver Configurations > Solution n > Time Dependent Solver (Time Stepping).
Time dependent problems sometimes (often?) have problems with convergence. Sometimes experimenting with different solvers can help.