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Old   July 22, 2010, 12:32
Default Vortex Shedding
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Nikhil Shastry Yelleswarapu
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Hi,

I've beent rying to model flow over bluff object to observe vortex shedding but havn't been able to achieve it. I only get one vortex at the beginning and then the system goes into steady state. I used 'Implicit unsteady', 'k-epsilon', 'RANS' and default settings for the time steps. The other parameters are as follows,

Velocity - 10m/s
PipeDiameter - 0.5m
Cylinderdiameter - 0.2m

Can anyone tell me where the problem might be?

Last edited by Nikhil Kumar; July 22, 2010 at 12:39. Reason: insufficient information
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Old   July 23, 2010, 13:01
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John
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The default time step is too large. Your mesh might be too coarse.
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Old   July 26, 2010, 05:07
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NVilius
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Hi!

Fisrt : check if under implicit unsteady you are using the second order scheme discretization!

Second: Check if the lateral boundaries are periodicities!

Third: Estimate the frequency of vortex sheding based on the Strouhal number (0.21) and set the time step to be at the most 1/10 of the computed period!

Regards!

Last edited by coolio; July 28, 2010 at 15:56.
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Old   July 28, 2010, 13:25
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Vinicius Girardi
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Also use LES or DES. RANS methods are not very suitable since your time step is to small...
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Old   December 7, 2010, 12:17
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Nikhil Shastry Yelleswarapu
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Thank you all for the reply.. I got it...
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