How to understand the Radial distribution function for TFM


For TFM, RDF_TYPE represents the “Radial distribution function (RDF) at contact”. Is it the RDF for particles? It also needs to be selected from its list even for particles with fixed diameters. I am confused about this selection.

Thanks for your help.

Kindly regards

The RDF is not the same as the Particle Size Distribution. RDF is used for TFM to represent probability of collision. It goes from 1 in very dilute region to infinity at maximum packing.

Thank you @jeff.dietiker . I have understood it.

Hi, Dr. Dietiker

For TFM simulation, it can be found that there are a lot of researchers using commercial solver FLUENT to conduct simulations. For gas-solid flow, it is common to see the radial distribution function, as shown in the first screenshot, used for the TFM simulation by using FLUENT, which seems not available in MFIX, as shown in the second screenshot, in which dm, dl and dml are used for the case of more than one solid phase.
As a consequence, does it mean that, to conduct the same simulation as reported in the paper, it is necessary to write UDS of radial distribution function?

Thank you very much.


Yes, if you want to use MFiX, you will need to write code for any rdf that is different from the ones available in MFiX.

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Hi, Dr. Dietiker

Can you please tell what is the function G_0AVE in module rdf_mod used for? It is failed to find it in the theory manual. Can you tell me how is the function G_0AVR defined based on G_0?
Thank you.

If you scroll down in the file, you have the corresponding reference for each rdf, for example:

  83 ! The Journal of Chemical Physics, Vol. 51(2):635-636.
  84 !---------------------------------------------------------------------//
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Thank you, Dr. Dietiker.
By the way, can you please tell which source code files should be adapted when a new radial distribution function is added? It seems it is not enough to only adapt the fortran file rdf_mod.f.

I think you need to add the RDF_TYPE enumerator in des/derived_types_mod.f and set it in check_data/check_solids_continuum.f. Look for RDF_TYPE or RDF_TYPE_ENUMERATOR in these files.

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