Ivar KJELBERG
COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted:
1 decade ago
8 apr 2011, 01:29 GMT-4
Hi
in which case ? in an eigenfrquency solver case ?, if so it's normal, the displacement in an eigenfrequency analysis are normalised, and have no absolute meaning. In V4.1 you can extract the mass matrix (settings of the eigenfrequency solver) in this way you normalise such that the square of the mass participation factors add up to the total mass, in this normalisation you have an information of the relative energy in the different modes, and you can check if you are considering enough modes.
Unfortunately, today COMSOL does only show the linear u,v,w mass participation factors, they have not normalised for the rigid body rotation (which add up to the respective inertias), but it's already a start ;) (does not exist in V3.5
If you are not in an eigenmode analysis it might be that you have missed the units and you are working in "m" instead of "um"
--
Good luck
Ivar
Hi
in which case ? in an eigenfrquency solver case ?, if so it's normal, the displacement in an eigenfrequency analysis are normalised, and have no absolute meaning. In V4.1 you can extract the mass matrix (settings of the eigenfrequency solver) in this way you normalise such that the square of the mass participation factors add up to the total mass, in this normalisation you have an information of the relative energy in the different modes, and you can check if you are considering enough modes.
Unfortunately, today COMSOL does only show the linear u,v,w mass participation factors, they have not normalised for the rigid body rotation (which add up to the respective inertias), but it's already a start ;) (does not exist in V3.5
If you are not in an eigenmode analysis it might be that you have missed the units and you are working in "m" instead of "um"
--
Good luck
Ivar