Non Linear Convergence Question
Posted: 24 May 2022, 18:37
Hi
We have been observing some convergence behavior for some electric machine models which we do not understand and would like some help with.
We have generally found that with coarse meshes our analyses converge fine but when we go to finer meshes the maximum number of iterations is reached.
I have attached two examples which are very similar. They are the same model and sif file, the only difference is a slight difference in mesh (in this case the mesh with bad convergence has slightly less elements, 8773, compared to the one with good convergence 8813, contrary to our general observation) . "Good Convergence" converges after 9 iterations.
The first few iterations of "Good Convergence" are below. The norm of the first iteration is 286
MAIN: -------------------------------------
MAIN: Time: 1/3: 2.500E-03
MAIN: -------------------------------------
MAIN:
ComputeChange: NS (ITER=1) (NRM,RELC): ( 286.15415 2.0000000 ) :: mgdyn2d
ComputeChange: NS (ITER=2) (NRM,RELC): ( 10390.471 1.8927923 ) :: mgdyn2d
ComputeChange: NS (ITER=3) (NRM,RELC): ( 3990.2400 0.89011328 ) :: mgdyn2d
ComputeChange: NS (ITER=4) (NRM,RELC): ( 3670.9340 0.83356917E-01 ) :: mgdyn2d
"Bad Convergence" reaches the maximum number of iterations of 50.
The first few iterations of "Bad Convergence" are as below. We notice that the norm on the first iteration is a very high value.
MAIN: -------------------------------------
MAIN: Time: 1/3: 2.500E-03
MAIN: -------------------------------------
MAIN:
ComputeChange: NS (ITER=1) (NRM,RELC): ( 0.88329967E+09 2.0000000 ) :: mgdyn2d
ComputeChange: NS (ITER=2) (NRM,RELC): ( 90784692. 1.6271999 ) :: mgdyn2d
ComputeChange: NS (ITER=3) (NRM,RELC): ( 42805029. 0.71831369 ) :: mgdyn2d
ComputeChange: NS (ITER=4) (NRM,RELC): ( 0.15274347E+09 1.1244110 ) :: mgdyn2d
Could you please help us to understand this different behavior between these models.
How does Elmer obtain the permeability of the elements using the non linear BH curve for the first iteration? This seems to be different for the two examples?
Thanks and Best Regards,
Paul
We have been observing some convergence behavior for some electric machine models which we do not understand and would like some help with.
We have generally found that with coarse meshes our analyses converge fine but when we go to finer meshes the maximum number of iterations is reached.
I have attached two examples which are very similar. They are the same model and sif file, the only difference is a slight difference in mesh (in this case the mesh with bad convergence has slightly less elements, 8773, compared to the one with good convergence 8813, contrary to our general observation) . "Good Convergence" converges after 9 iterations.
The first few iterations of "Good Convergence" are below. The norm of the first iteration is 286
MAIN: -------------------------------------
MAIN: Time: 1/3: 2.500E-03
MAIN: -------------------------------------
MAIN:
ComputeChange: NS (ITER=1) (NRM,RELC): ( 286.15415 2.0000000 ) :: mgdyn2d
ComputeChange: NS (ITER=2) (NRM,RELC): ( 10390.471 1.8927923 ) :: mgdyn2d
ComputeChange: NS (ITER=3) (NRM,RELC): ( 3990.2400 0.89011328 ) :: mgdyn2d
ComputeChange: NS (ITER=4) (NRM,RELC): ( 3670.9340 0.83356917E-01 ) :: mgdyn2d
"Bad Convergence" reaches the maximum number of iterations of 50.
The first few iterations of "Bad Convergence" are as below. We notice that the norm on the first iteration is a very high value.
MAIN: -------------------------------------
MAIN: Time: 1/3: 2.500E-03
MAIN: -------------------------------------
MAIN:
ComputeChange: NS (ITER=1) (NRM,RELC): ( 0.88329967E+09 2.0000000 ) :: mgdyn2d
ComputeChange: NS (ITER=2) (NRM,RELC): ( 90784692. 1.6271999 ) :: mgdyn2d
ComputeChange: NS (ITER=3) (NRM,RELC): ( 42805029. 0.71831369 ) :: mgdyn2d
ComputeChange: NS (ITER=4) (NRM,RELC): ( 0.15274347E+09 1.1244110 ) :: mgdyn2d
Could you please help us to understand this different behavior between these models.
How does Elmer obtain the permeability of the elements using the non linear BH curve for the first iteration? This seems to be different for the two examples?
Thanks and Best Regards,
Paul