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vortex shedding frequency

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Old   May 28, 2010, 02:13
Default vortex shedding frequency
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NAVEEN.K.M
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hi everybody,

i am working on flow around a circular cylinder of diameter 2m using OpenFOAM 1.4.1 and 1.5 versions past 1 month. I am getting pressure and velocity contours correctly in both the versions.I am facing difficult to get the vortex shedding frequency in OpenFOAM.

Can you please suggest me how to get the strouhal number and vortex shedding frequency in OpenFOAM 1.5.

Flow conditions (laminar flow):

Reynolds number---------> 150 (based on cylinder diameter)
velocity------------------------>1 m/s
viscosity------>0.01333 m2/sec(based on cylinder diameter)
diameter of cylinder--------> 2 meters
OpenFOAM version-------->1.4.1, 1.5
solver----------------------------->icoFoam

can you please give me a suggestion how to get these values using the probes function and FFT.

waiting for your response

Regards,

Naveen
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Old   July 19, 2010, 02:10
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Jie
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Please correct me if I am wrong.

You can catch the time series data for Cd or Cl and use FFT to get the spectra to identify the St.
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Old   July 19, 2010, 02:58
Default vortex shedding frequency
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NAVEEN.K.M
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hi jiejie,

Thanks for your reply..........

I have successfully completed that work 1 month back using OpenFOAM...anyway thanks for your kind response...


Regards

Naveen
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Old   December 2, 2010, 15:44
Default FFT for a sound spectrum
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Bertrand Delvaux
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Hello,

I read you are talking about FFT from probes. I would need this for my case.
How do we proceed FFT in OpenFOAM, or is there any documentation I could find on this?

Thank you!

Bertrand
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Old   March 19, 2011, 11:44
Default strouhal number
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s.rasoul_varedi
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hi all of foamers,

can any one tell me how to calculate strouhal number or shedding frequency?
( OF 1.5-dev)

waiting for your response...
tanks
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Old   March 20, 2011, 08:22
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Patricio Bohorquez
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You could proceed as described in the following paper:

Bohorquez, P., Sanmiguel-Rojas, E., Sevilla, A., Jiménez-González, J., Martínez-Bazán, C. Stability and dynamics of the laminar wake past a slender blunt-based axisymmetric body. Journal of Fluid Mechanics (in press)
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Old   March 20, 2011, 18:32
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s.rasoul_varedi
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hi dear pbohorquez
thanks for your paper atachment, i think that it is very helpful for me but :

i am working on flow around a circular cylinder of diameter 0.025 & Re=150 using OpenFOAM 1.5-dev versions & get pressure and velocity contours correctly,
i have two question:
1) when i want to calculate Drag and lift coeff with add a related code to controlDict, the answer of this work not validate. why??( answer of drag is very low, while drag in Re=150 must be nearly 1)
2) how can i calculate vortex shedding frequency
3)if have another related refrence for my work, i am very glad that atached link for me

i chose this parameter for calculate cd & cl =>
Aref=0.025
Lref=0.0128
magUinf=0.006
rho=1000
liftDir=(0 1 0)
dragDir=(1 0 0)


tank a lot
waiting...
Rasoul
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Old   March 21, 2011, 06:49
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Patricio Bohorquez
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To compute the St number you should include in the controlDict the 'sets' and generate during the numerical simulations the samples of the velocity field at the point you are interested in. Then read the information you generated with some software. I employed Matlab to read the data and ezfft to compute the Fourier transform.

I did not calculate the Drag and Lift, so I can not help.
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Old   December 8, 2012, 22:59
Question flow around cylinder..
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Rishitosh Ranjan
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hiii..

i m also new in dis CFD area...
i m working on flow over two side by side cylinders... @ Re= 100 and 200..
i got good results..

but i want to find out Strouhal number for all cases...

i came to know by finding shedding frequency with help of FFT, using cofficient of lift data, in fluent 13.0 we can calculate Strouhal number...

but i m getting helpess..

how to use FFT to find shedding frequency....?????
-Rishi
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Old   May 17, 2014, 10:12
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Hi dear all,
Rishitosh, did you find how to compute the St nmbr ?
Thanks,

Mehrez
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