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  • FLUENT - Unsteady Flow Past a Cylinder - Step 5

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titleCalculating Time Step Size

The Strouhal number for flow past cylinder is roughly 0.183 as reported by Williamson (link).
In order to capture the shedding correctly, we should have at least 20 to 25 time steps in one shedding cycle. Let's use 25 for our case.
Sr = 0.183 = f*D/U
For our case, D = 2, U = 1
Therefore, shedding frequency f = 0.0915
Cycle time, t = 1/f = 10.9 sec
Therefore, Time Step Size = 10.9/25 = 0.436 sec

 Enter 0.436 for Time Step Size (s). Enter 30 for Max. Iterrations per Time Step. Enter 600 for Number of Time Steps. Click Apply. Click Iterate to start the iterations.

Go to Step 6: Analyze Results

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