Incorrect Strouhal number for flow over a cylinder simulations

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• Last Post 13 March 2019
asaif61 posted this 05 March 2019

I am trying to simulate the flow separation around a circular cylinder for Re=100. The drag and lift coefficients seem to match with the literature . However I am getting a low value of the Strouhal number which should be in the range of   1.6-1.7, but i am getting 0.03. tried varying the time step still no luck. Can anybody please help me solve this problem?

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rwoolhou posted this 05 March 2019

Check the values you're using: what velocity etc are used in the theory/paper and are you taking the same data from Fluent?

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asaif61 posted this 06 March 2019

I am using the same values of velocity and viscosity which is:

velocity = 1 m/s

viscosity = 0.01 kg/m-s

And I also  used the same solution methods as the papers.

Thanks.

abenhadj posted this 06 March 2019

What is the period required to be run? This has to be based on your Strouhal number. That period has to be at least resolved with 60-100 time steps. You will need at last two periods to be calculated

Best regards,

Amine

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asaif61 posted this 07 March 2019

Taking Stroual number to be 0.165 (used in the literature), period is 6.06 s. And I have resolved it for 80 time steps. So, the time step I have taken is 0.075 and run it for 1600 time steps.

Should I lower the time step even more?

Thanks.

abenhadj posted this 08 March 2019

Actual that corresponds to a Fluent workshop. Run some more periods and start writing after one period. Are u doing the fft in fluent?

Best regards,

Amine

asaif61 posted this 13 March 2019

Yes, I am doing the FFT in fluent.