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# Modal analysis - Fluid structure interaction - Skipping frequencies - ANSYS APDL

## Modal analysis - Fluid structure interaction - Skipping frequencies - ANSYS APDL

(OP)
Hi All,

I d like asking suggestion about the following matter. I am performing a unsymmetric modal analysis of a tank filled with fluid. Modal shapes of the fluid are convective (e.g. 0.1Hz~1Hz) and impulsive (e.g. 2Hz~20Hz). The problem is that the convective modes are a lot (1000 modes?) therefore I cannot calculate convective and impulsive modal shapes of the fluid (and structure) in one simulation because I would end up having thousands of modal shapes.

--> There is any way to skip and/or select a range of frequencies in the unsymmetric modal analysis?
Currently I am using the following commands:

ANTYPE, MODAL
MODOPT, UNSYM, 20, 0.01, 1,,, BOTH (for the convective modal shapes)
MODOPT, UNSYM, 200, 2, 20,,, BOTH (for the impulsive modal shapes)

--> There is a way to calculates modal shapes in two frequencies range in the same simulations? (e.g. 0.1Hz~1Hz and e.g. 2Hz~20Hz)
Thank you!

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