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-   -   Vortex Shedding (http://www.cfd-online.com/Forums/star-ccm/78474-vortex-shedding.html)

Nikhil Kumar July 22, 2010 12:32

Vortex Shedding
 
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?

nomad July 23, 2010 13:01

The default time step is too large. Your mesh might be too coarse.

coolio July 26, 2010 05:07

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!

Vinicius July 28, 2010 13:25

Also use LES or DES. RANS methods are not very suitable since your time step is to small...

Nikhil Kumar December 7, 2010 12:17

Thank you all for the reply.. I got it...


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