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Time step size

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Old   December 22, 2005, 20:05
Default Time step size
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I've modeled vortex shedding using a time step that is 1/30 of the period of shedding(Fluent manual suggests at least 1/20) with good results. For the Re #'s and Str #'s I've been looking at this corresponds to a step of approx. 0.03 s. Yet, I've read several postings where someone is modeling a similar phenomenon, shedding from a cir. cylinder for example, and they're using a delta t aound 0.00001. Why so small?
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Old   December 24, 2005, 00:00
Default Re: Time step size
Muhammad Shakaib
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The period of shedding and time step required for flow around cylinder in narrow channels is much less. May be these postings are for these cases.

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Old   December 26, 2005, 00:39
Default Re: Time step size
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Sounds reasonable. I've actually modeled a thin plate in a channel for different blockage ratios and found that the Str# does increase significantly, but I didn't have to decrease my time step size quite so small to capture 1/30th of the period. Thanks
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