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Reason for asymmetry in symmetric geometries

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Old   June 10, 2010, 02:20
Default Reason for asymmetry in symmetric geometries
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say I have a symmetric geometry like a circular cylinder. the grid is perfectly symmetric around the cylinder and the inlet profile is also symmetric. still why do we get alternate vortex shedding? what is the numerical reason?

in real life scenario there is some asymmetry in the inlet flow which might trigger the asymmetric vortex shedding. but why does this happen in a perfect cfd simulation?
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Old   June 10, 2010, 08:13
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It is true that in real life there may be some asymmetry that can trigger an asymmetry in a flow, which might not happen in a "perfectly" symmetric CFD simulation. But no CFD simulation is perfectly symmetric, due to such things as round-off error. Also, you are failing to consider the possibility that the Navier-Stokes equations can support solutions that are time-varying and only symmetric in a time-averaged sense.
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