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Magnetostatics: Convergence criteria of the nonlinear solver are met but not all linear solver conditions are fulfilled
Posted 17.08.2022, 05:48 GMT-4 Electromagnetics, Studies & Solvers Version 6.0 0 Replies
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I'm using the "magnetic fields, no currents" module for stationary simulations of nonlinear magnets inside a homogeneous external magnetic field. The simple setup consists only of several blocks of nonlinear magnetic material inside a box/sphere of perfect vacuum. The external field is applied to the boundaries of the system.
Solving this model often results in the above mentioned error: Convergence criteria of the nonlinear solver are met but not all linear solver conditions are fulfilled, when the nonlinear magnet starts to saturate. It most often occurs when using a direct solver for the linear solver. Changing the nonlinear solver between automatic Newton, automatic highly nonlinear Newton and double dogleg, can help or be detrimental.
I don't understand why such a simple setup is so numerically fragile. There are no extreme aspect ratios, no undefined material properties. What could cause such problems for the direct solver? Can it be a mesh problem? I've tried different mesh settings and also adaptive mesh refinement without success. Or the initial value?
Hello Severin Selzer
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