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-   -   Modal Analysis - Beta Features - Arnoldi (http://www.cfd-online.com/Forums/fluent/67237-modal-analysis-beta-features-arnoldi.html)

Michael Kolb August 8, 2009 13:14

Modal Analysis - Beta Features - Arnoldi
 
Hey all.

I'm using the Beta Features of Fluent v12 to get a modal analysis of a pipe.
It's simply a pipe with a temperture gradient somewhere.
No massflow.
The matrix the modal analysis has a size of about 75.000.
I think I understood the basics of ARPACK which is used here.

My questions are:
1) Can I estimate the time it will need?
2) Why does it need fewer iterations if I want more frequencies? That is really strange.
3) Is the Arnoldi Error calculated with something like: A*x=A*A*x
4) How do I know if the solutions make physical sense. It's simple for my pipe, but how will I know it for my combustion chamber?

Thats for your help, its hard to find informations an the beta features.

Geetings
Michael


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