The simulation should analyse the following problem: A magnet is passing by a piece of iron. (sketch.jpg) As Study Step I chose Time Dependent.
At first I tried a simple problem, where the magnet was not moved at all. The magnet is just slowly switched on and off by using a smoothed rectangle function. This simulation takes about 2 Minutes on my PC, the solutions are mostly converging very well and the time steps are rather large. (convergence weak field.jpg; step size weak field.jpg; graphics weak field.jpg)
But if I increase the strength of the magnet by a factor of 10 (magnetization.jpg; 1000 A/m works, 10000 A/m does not), without changing anything else, convergence gets worse and time steps get very small until the simulation ends with an error after 20% of the time. (convergence strong field.jpg; step size strong field.jpg)
COMSOL Error
The following feature has encountered a problem:
Repeated error test failures. May have reached a singularity.
Time: 0. 1956460958724214
Last time step is not converged.
- Feature: Time-Dependent Solver 1 (sol1/t1)
- Error: Repeated error test failures. May have reached a singularity.
I searched for this error in the forum and could not find the mistake in my model. The mesh looks good (mesh.jpg), the magnetization is smoothed both in time and space, there are no sudden changes in the magnetization, there are no sharp start conditions.
Any ideas why it does not converge?
(The magnet is not modelled as a real mass, because later I do not want to move a real mass in my simulation. Instead I defined a magnetisation, which is dependant of the coordinates of space and time. I did not use a moving mesh, because it is not suitable for complex geometries in 3D.)
At first I tried a simple problem, where the magnet was not moved at all. The magnet is just slowly switched on and off by using a smoothed rectangle function. This simulation takes about 2 Minutes on my PC, the solutions are mostly converging very well and the time steps are rather large. (convergence weak field.jpg; step size weak field.jpg; graphics weak field.jpg)
But if I increase the strength of the magnet by a factor of 10 (magnetization.jpg; 1000 A/m works, 10000 A/m does not), without changing anything else, convergence gets worse and time steps get very small until the simulation ends with an error after 20% of the time. (convergence strong field.jpg; step size strong field.jpg)
COMSOL Error
The following feature has encountered a problem:
Repeated error test failures. May have reached a singularity.
Time: 0. 1956460958724214
Last time step is not converged.
- Feature: Time-Dependent Solver 1 (sol1/t1)
- Error: Repeated error test failures. May have reached a singularity.
I searched for this error in the forum and could not find the mistake in my model. The mesh looks good (mesh.jpg), the magnetization is smoothed both in time and space, there are no sudden changes in the magnetization, there are no sharp start conditions.
Any ideas why it does not converge?
(The magnet is not modelled as a real mass, because later I do not want to move a real mass in my simulation. Instead I defined a magnetisation, which is dependant of the coordinates of space and time. I did not use a moving mesh, because it is not suitable for complex geometries in 3D.)