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Useful LES tools in Fluent - Part 4

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Useful LES tools in Fluent - Part 4

Posted March 7, 2014 at 03:59 by sbaffini

This is a routine to perform a remap of fields from an interior surface to an inlet surface during the computation. In practice this can be used to produce an LES inflow belonging to the class of the so called "precursor methods". Still, this is actually done in parallel with the main computation and not in advance.

The attached pdf file contains an explanatory image of the method while the .c routine should be sufficiently commented to be readily usable by anyone who actually knows what i'm talking about. If you don't, then you don't need it.

The routine only works in parallel (a serial version is available on request but its use is pointless in LES) and has been tested on straight circular and square ducts, both with structured and unstructured grids.

When compared with the default methods in Fluent (Vortex Method and Spectral Synthesizer) on the same number of cells, it is found to be around the 18% faster on average (different parallel partitions, load balances and hardware architectures). When the parallel partitioning is optimized the saving is higher.

A preliminary testing of the procedure has been presented here:

http://proceedings2012.caeconference...icoMilano.html

While additional details will be present in my forthcoming Ph.D. thesis, which i will share as soon as i will defend it.

The auxiliary flow is driven by a fixed source term (which nonetheless can be easily modified). An alternative version based on a PID controller to fix the mass flow rate and/or an additional integral parameter (say, the swirl number) is also available on request. However, this PID version has not been toroughly tested and some additional work might be needed.
Attached Files
File Type: c remap_par.c (14.4 KB, 183 views)
File Type: pdf remap.pdf (24.2 KB, 287 views)
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Comments

  1. Old Comment
    Hi!

    Thank you for this work - it seems very interesting, and it could help me with my simulations. When I download the text file, however, the entire code appears as one big chunck of text. Could you maybe reupload the text file, where the code can be better understood or can you maybe just post the code somewhere on this website?

    Thanks in advance for your help!
    permalink
    Posted November 8, 2015 at 13:38 by TimotheusFlavii TimotheusFlavii is offline
  2. Old Comment
    sbaffini's Avatar
    You have 3 options:

    1) Open it with wordpad
    2) Open it under Linux
    3) Do "unix2dos remap_par.c" in a linux shell, then use it under windows
    permalink
    Posted November 8, 2015 at 14:09 by sbaffini sbaffini is offline
  3. Old Comment
    Hi,

    this is a very nice tool! I have a periodic boundary condition which should handle translation and rotation. Your approach helps me already. However a real two way periodicity would be even better. Do you have a suggestion on that?

    Best regards!
    permalink
    Posted June 21, 2016 at 07:08 by spoink spoink is offline
  4. Old Comment
    sbaffini's Avatar
    I don't know if i understood correctly what you mean by two-way periodicity.

    If you mean to make the copied section aware of the main domain where it is copied, then it is not possible and does not make sense, because the copied section already has all the information it requires. You could instead simply define the copied section to be in the domain and not out of it (as some OpenFoamers use to do), but my experience is that such coupling is only detrimental to the stability.

    If instead you mean to apply it between multiple couples of faces, then you can simply compile different versions of the UDF, one for each couple of faces.

    Quote:
    Originally Posted by spoink View Comment
    Hi,

    this is a very nice tool! I have a periodic boundary condition which should handle translation and rotation. Your approach helps me already. However a real two way periodicity would be even better. Do you have a suggestion on that?

    Best regards!
    permalink
    Posted June 21, 2016 at 12:20 by sbaffini sbaffini is offline
 

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