A problem with Comsol’s Axial Magnetic Bearing example
Posted Oct 19, 2020, 6:13 AM EDT AC/DC & Electromagnetics Version 5.5 1 Reply
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Hello all, I have downloaded the example “Axial Magnetic Bearing Using Permanent Magnets” (Application ID: 14367) to learn how to calculate the force between two permanent magnets. Without making any changes (except removing the parametric sweep and setting dz=0), I tried to verify that the force acting upon each magnet is the of same value and opposite direction. The modeling instructions do not specify a certain mesh resolution. Since electromagnetic force calculations require high resolution, it was no wonder that force equality was not obtained for the default element size.
I started to increase the mesh density, and allegedly reached force equality for the predefined “Extremely Fine” element-size, but with a maximal element size of 0.16mm (which is 10 times smaller than its nominal value). When increasing the resolution even further to 0.05mm, the equality held, but the value dropped by two orders of magnitude(!). I Increased the resolution to 0.01mm and left the simulation to run during night, but by morning it progressed only by ~5%.
I must emphasize that I this is a 2D simulation, so it’s hard to imagine what kind of computational resources are required to calculate forces for my 3D simulations. So am I missing something or is there a problem with this example? Should this relatively simple 2D simulation be so computationally expensive or is there still hope for 3D cases?
Thank you for your attention and best regards, Nadav Goulinski