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Turbulence Modelling with DES/LES

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Old   June 24, 2018, 14:47
Question Turbulence Modelling with DES/LES
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Hi there,

From my reading around the forum I have learned that LES can only be enabled in a 3D simulation. This makes sense to me as this turbulence is inherently a 3D problem and it wouldn't make sense to employ it in 2D. It also can't be switched on in Fluent for 2D.

My question is this, if LES can't be enabled in 2D, how can DES be an option in 2D for Fluent? My understanding of DES is that it is a combination of RANS and LES where RANS is used at the boundary layer and LES is used elsewhere.

If anyone could shed some light on my confusion, it would be much appreciated.

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Old   June 25, 2018, 10:47
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You can do 2D LES in Fluent but the option is hidden except for people that know how to turn it on are able to. Type this into the TUI and hit enter/return:

(rpsetvar 'les-2d? #t)
This will make LES appear in the viscous models and allow you to use it.

Note you should type it in yourself, copy and paste usually does not work because of the way characters are coded. If this doesn't work, open up the case file with a text editor and find the line that reads:

(les-smag-const 0.1)
(les-2d? #f)
(les-cpld-diss-coeff 0.2)
and change it to
(les-smag-const 0.1)
(les-2d? #t)
(les-cpld-diss-coeff 0.2)
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des, fluent, les, turbulence

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