Learning Forum

[Panixm.25]

hello everyone im trying to do a harmonic response analysis for a compressor rotor blade in ansys workbench. i have a few questions: 1- to my understanding you can't have rotordynamic elements in harmonic analysis like rotational velocity. but i need to draw a campbell diagram of the blade and its not possible without having a rotational velocity applied to the blade. so any suggestions regarding this? 2- one of my goals is to create an frf diagram (deformation against frequancy) for the blade. for loading, i apply a constant pressure on the blade surface and a fix support to the base of the blade but the results have no diffrenece with the results of blades modal analysis (the frequancies are the same). is this normal or am i doing something wrong?

[dlooman]

1. Campbell Diagrams are based on modal analyses, not harmonic.  
2. You can specify rotational velocity with a commands object using the OMEGA command in a harmonic analysis.  Then you should see a frequency shift.  You can confirm that the centrifugal forces due to omega have been suppressed by doing analysis without any loads.

[Panixm.25]

Thank you sir. I tried to obtain the diagram throgh ansys modal. The problem is when i apply the velocity in modal analysis, it asks me to turn the coriolis effect on, which requires to turn on the damped option and i do not want to solve this analysis in damped state. I watched a video on youtube that runs the exact same analysis as mine and they didn't have to turn this options on. Can you guid me on what should i do to have the diagram in modal without having to deal with damping?

[dlooman]

The only reason for a Campbell Diagram is to account for the coriolis effect on the natural frequencies.  Since the coriolis effect is proporitional to "velocity" the solver treats it like a form of damping, even though it isn't really damping.   Why don't you want to use a damped solver?