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-   -   How to get the vortex frequency (http://www.cfd-online.com/Forums/cfx/106542-how-get-vortex-frequency.html)

mohammad August 31, 2012 11:15

How to get the vortex frequency
 
Dear all,
I have simulated a finite span S809 blade with DES using transient simulation.

For analyzing the noise generated by the vortical system, I need to have the vortex shedding frequency of the simulation...

Can anyone tell me how to get (calculate) it in the post processing of the results?

Tnx in advance

ghorrocks September 1, 2012 07:33

Put a monitor point (of a few points) somewhere at the edge of your domain and output pressure there. You can get the simulated pressure variation (ie noise) from that.

mohammad September 1, 2012 10:52

Dear Glenn Horrocks,

I forgot to add a piece of information which might be important....
My case is a Synthetic Jet Actuator case, and I monitored the lift and drag fluctuations duiring the transient run, My non-dimensional frequecy is F+ = 0.97, thus the lift and drag frequncy are the same and is very near to the actuator frequency.
We know that the Lift is the direct result of the pressure distribution.
Now my question is: " Can I safely say the vortex shedding frequency is the Lift and Drag frequency? "

Regards

ghorrocks September 2, 2012 19:19

I have no idea - this is your research so how am I going to know that? It is up to you to work that out.

mohammad September 2, 2012 22:56

Quote:

Originally Posted by ghorrocks (Post 379923)
I have no idea - this is your research so how am I going to know that? It is up to you to work that out.

Anyhow, I highly appreciate your favor

D.B September 5, 2012 05:16

Hi,
From what I know, it is not necessary that the lift drag fluctuation frequency is same as vortex shedding frequency. As glenn said you could check it with your monitor point plot minimum pressure in a plane behind your geometry against time and find out the frequency from that.


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