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 Deloat February 25, 2008 02:52

strouhal number

Hi,

Does anyone knows how to find the Strouhal number in Post-CFX? I am modelling constant flow past a cylinder, and wants to figure out the Strouhal number of that flow?

Any ideas guys? Thanks a lot.

Deloat

 andy20 February 25, 2008 06:08

Re: strouhal number

Just plot a chart of pressure behind the cylinder vs. time and estimate the period of the variation? Use that to compute the shedding frequency. I assume you know the radius and velocity already - so together that should allow you to compute the Strouhal number. I don't think there's much more to it....

(By the way be careful to account for the fact that with alternate vortex shedding from each side of the cylinder, the frequency of the drag force variation is twice that of the lift force variation...)

Good luck, Andy

 Rogerio Fernandes Brito February 25, 2008 07:02

Re: strouhal number

Trying using Origin 7.5 software to extract this frequency!

 Dre February 25, 2008 10:23

Re: strouhal number

What I do is plot the vorticity and set the scale so I can see the vortex better. Then I do an animation and export the frames as images. Then all I have to do is match 2 frames. Since my timesteps are constant, I have the time between two identical frames.

 pasu February 27, 2008 15:11

Re: strouhal number

I believe Strouhal number is only used when the flow is oscillatory. If you are modeling with constant flow then it wont help.

 wake March 11, 2008 04:19

Re: strouhal number

dear pasu

But there is a defenition of strouhal number for constant flow also the frequency as vortex shedding frequency and diameter as length scale for a given velocity.

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