steveworks123
Electrical
- Aug 27, 2006
- 5
Hi all,
As we know, a permanent magnet residing in the infinte air will not generate any force on the magnet itself. So if we simulate this situation in ANSYS, we should get a ZERO force on the magnet. However, I found there is some force on the magnet, which is large enough so that cannot be simply neglected! I tried to solve this problem for sooo long and almost my whole summer was wasted on this thing! It is really, really painful.............
I set the relative permeability 'murx' 5 and coercive force 'mgzz'129900 A/m for the magnet(magnitization only in z direction, mgxx and mgyy are both zero), and 'murx' 1 for air.
The magnet is cylindrical, centered at the global coordinates origin whit z axis as its longitudinal axis. Its radius is 5m, and the height is 10m (from z=-5 to z=5). This whole structure is encompassed by an air domain in the shape of sphere with radius 9m, centered at global origin as well. You can see that the whole model is symmetric about the origin and all three x,y,z axis.
I use element solid98 MAG to mesh the magnet and the air domain volumes. Meanwhile, I use element infin47 to mesh the outside surface of the air domain sphere.
The model is solved with RSP, with JCG solver adopted.
THE RESULTS is:
SUMMARY OF FORCES BY VIRTUAL WORK
Units of Force: ( N )
Component Force-X Force-Y Force-Z
magnet 0.60467E+03 0.21016E+04 -0.40892E+04
___________________________________________________
SUMMARY OF FORCES BY MAXWELL STRESS TENSOR
Units of Force: ( N )
Component Force-X Force-Y Force-Z
magnet 0.10967E+05 0.36619E+05 -0.74172E+04
WHY ARE THERE SUCH FORCES?! THEY SHOULD BE ZERO!! OH MY GOD~
WHO CAN SAVE ME??? please!
THANK YOU SOOOOOOOOOO MUCH!
As we know, a permanent magnet residing in the infinte air will not generate any force on the magnet itself. So if we simulate this situation in ANSYS, we should get a ZERO force on the magnet. However, I found there is some force on the magnet, which is large enough so that cannot be simply neglected! I tried to solve this problem for sooo long and almost my whole summer was wasted on this thing! It is really, really painful.............
I set the relative permeability 'murx' 5 and coercive force 'mgzz'129900 A/m for the magnet(magnitization only in z direction, mgxx and mgyy are both zero), and 'murx' 1 for air.
The magnet is cylindrical, centered at the global coordinates origin whit z axis as its longitudinal axis. Its radius is 5m, and the height is 10m (from z=-5 to z=5). This whole structure is encompassed by an air domain in the shape of sphere with radius 9m, centered at global origin as well. You can see that the whole model is symmetric about the origin and all three x,y,z axis.
I use element solid98 MAG to mesh the magnet and the air domain volumes. Meanwhile, I use element infin47 to mesh the outside surface of the air domain sphere.
The model is solved with RSP, with JCG solver adopted.
THE RESULTS is:
SUMMARY OF FORCES BY VIRTUAL WORK
Units of Force: ( N )
Component Force-X Force-Y Force-Z
magnet 0.60467E+03 0.21016E+04 -0.40892E+04
___________________________________________________
SUMMARY OF FORCES BY MAXWELL STRESS TENSOR
Units of Force: ( N )
Component Force-X Force-Y Force-Z
magnet 0.10967E+05 0.36619E+05 -0.74172E+04
WHY ARE THERE SUCH FORCES?! THEY SHOULD BE ZERO!! OH MY GOD~
WHO CAN SAVE ME??? please!
THANK YOU SOOOOOOOOOO MUCH!