Normalized eigenvectors
Normalized eigenvectors
(OP)
Hi,
Does anyone know how the eigenvectors are normalized in cyclic symmetry analysis of ANSYS 7.0?
By the way, I found the following information in ANSYS website.
In modal cyclic symmetry, this becomes even more complicated because of the presence of the duplicate sector. Here the mass normalization is [ [phi]a~ [M] [phi]a + [phi]b~ [M] [phi]b =1]. When two sectors are used, the scaling factor of sqrt(1/2) is still valid, but it should be applied on the magnitude: i.e, sqrt (real**2+imaginary**2).
......When I conduct this calculation, I can't get the unit matrix. Please let me know if you're familier with this.
Tommy
Does anyone know how the eigenvectors are normalized in cyclic symmetry analysis of ANSYS 7.0?
By the way, I found the following information in ANSYS website.
In modal cyclic symmetry, this becomes even more complicated because of the presence of the duplicate sector. Here the mass normalization is [ [phi]a~ [M] [phi]a + [phi]b~ [M] [phi]b =1]. When two sectors are used, the scaling factor of sqrt(1/2) is still valid, but it should be applied on the magnitude: i.e, sqrt (real**2+imaginary**2).
......When I conduct this calculation, I can't get the unit matrix. Please let me know if you're familier with this.
Tommy





RE: Normalized eigenvectors
MODOPT, Method, NMODE, FREQB, FREQE, PRMODE, Nrmkey
The Nrmkey controls this normalisation by using either
OFF — Normalize the mode shapes to the mass matrix (default).
ON — Normalize the mode shapes to unity instead of to the mass matrix. If a subsequent spectrum or mode superposition analysis is planned, the mode shapes should be normalized to the mass matrix (that is, Nrmkey = OFF).
So by default, these are normalised to the mass matrix. To get the these normalised to unity, use Normkey = on, or go to:
Main Menu>Preprocessor>Loads>Analysis Type>Analysis Options
Main Menu>Solution>Analysis Type>Analysis Options
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See FAQ569-1083 for details on how to make best use of Eng-Tips.com
RE: Normalized eigenvectors
Thank you for your response.
Yes, I turned off the MODOPT option.
Then, I get mode shapes in real and imaginary form. (for basic and duplicate sector).
My question is how I can compute the unit matrix using those mode shapes and mass matrix of the basic sector.
Tommy