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Old   November 26, 2007, 06:59
Default LES mesh guidelines
  #1
John Deas
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Hi,

I would like to use Fluent for LES calculations. I first need to calculate established flow in a 3d wall bounded channel periodical only in longitudinal direction. My main concern is that the documentation only gives few advices concerning mesh requirements : "There are no computational restrictions on the near-wall mesh spacing. However, for best results, it might be necessary to use a very fine near-wall mesh spacing (on the order of y+=1)."

Can someone point me to more precise recommendations ? I imagine that more precise guidelines such as x point in viscous zone, y in buffer zone, z in log zone might be available.

Thanks,

JD
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Old   November 30, 2007, 22:22
Default Re: LES mesh guidelines
  #2
Sandeep Jella
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Near wall and LES is just plain bad! Piomelli (review of LES) reports DNS type mesh requirements for wall flows...I suggest DES with the k-omega SST....for FLUENT.

How to get a good near wall mesh for DES? Just google "Young Person's GUide to Detached Eddy Simulations" by Spalart and you'll have enough to ponder.

As for LES, its true what the manual says - go crazy. Best thing to do is try piomelli's method. Get a solution monitor into the near wall layers and keep plotting the velocity profile. If its coarse you'll get flat profiles, keep refining until it looks physical (logarithmic) and then tune further keeping an eye on the experimental data.

Simply no way around it..

Academic codes may be better tuned...
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Old   December 1, 2007, 05:56
Default Re: LES mesh guidelines
  #3
pankaj saha
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hi, i am using les of channel flow by academics code..i have also some problem ....could u plz share some disscussion with me..
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