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Does laminar mean DNS?

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Old   April 21, 2013, 11:13
Default Does laminar mean DNS?
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Kai Zhang
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HI everyone!
I'm doing flow around cylinder at Re=100, and I chose laminar as the RASModel in RASproperties file. Dose it mean the simulation is running in Direct numerical simulation?
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Old   April 21, 2013, 17:11
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Lieven
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That is indeed what it means, pretty cool he ;-).

But note that if the flow is turbulent, a very fine mesh is required to get an accurate result. This is in fact already the case for you (you can check the discussion on the flow regimes at http://en.wikipedia.org/wiki/Reynolds_number ). So to get accurate results for the Re = 100, you should:
* run in 3D
* do a transient simulation
* perform a grid sensitivity study (to find the required number of cells)

If any of the above is not achievable, you should keep Re < 40 in which case the flow should be laminar so that a 2D, steady state, crude mesh simulation should be acceptable (if it is an infinite cylinder). Note however that even in this case turbulent structures might appear due to numerical inaccuracies.

Cheers,

L
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