frequency of modes decrease with flow rate?
frequency of modes decrease with flow rate?
(OP)
I am working with a fairly involved flow induced vibration test. The main component of the structure involves a high fluid (water) velocity down through (not around) an annulus. One of the first things we are seeing in the data is that the first few modes seem to move down in frequency as flow rate increases. This seems counter-intuitive, but I think what we are seeing is real. Is there some effect of velocity similar to a Coriolis force that would increase the effective mass of a system as the fluid velocity increases? The structure is stainless steel and the temperature is well controlled so there is no temp increase with flow rate.





RE: frequency of modes decrease with flow rate?
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RE: frequency of modes decrease with flow rate?
This section of your Reference "10.5 ANNULUS AT HIGH REYNOLDS NUMBERS" caught my eye.
Walt
RE: frequency of modes decrease with flow rate?
The decrease in stiffness with flow would cause reduction in resonant frequency of center structure with flow
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RE: frequency of modes decrease with flow rate?
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RE: frequency of modes decrease with flow rate?
RE: frequency of modes decrease with flow rate?
I am beginning to think this might be more connected to pressure, or the pressure drop. the main resistance is located after the annulus, and pressure is controlled after that resistance so the pressure in the annulus will increase with flow rate. I realize this does point towards entrapped air at some point but they are pretty meticulous in their venting.
RE: frequency of modes decrease with flow rate?
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RE: frequency of modes decrease with flow rate?
When you use the term modes are you refering to the frequency content of flow induced motion?
RE: frequency of modes decrease with flow rate?
RE: frequency of modes decrease with flow rate?