The first thing to do is to determine the cause of the vibration. Is it caused by:
1) acoustics, flow in the pipe
2) pulsation, pressure fluctuations across elbow-elbow pairs
3) mechanically induced, pump vibration at the nozzle
Items 1 and 2 are solved in a "similar" fashion, by guessing an applied force magnitude, and then scaling the force based on measured response. For acoustics, the direction of the force is usually perpendicular to flow direction, while pulsation is axial.
A <em>"uniform pulsation"</em> problem can be evaluated in
CAESAR II using the Harmonic Solution method. A step by step procedure for this has been outlined in a previous post - see
http://www.coade.com/ubb/Forum1/HTML/000092.html .
Note, the vibration magnitudes that you have measured are what you want to use to scale the driving force you specify.
Item 3 can be solved by measuring the pump nozzle displacement and frequency, and using these values as the load input.
In every case, the percent critical damping can be used to tweak the response.
Note, this is perhaps the most <em>uncomfortable</em> analysis (for engineers) that can be performed by
CAESAR II, since you have to guess at magnitudes and directions to <em>simulate</em> the loading on the real system.
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Regards,
Richard Ay (COADE, Inc.)
