Volume fraction in granular equations - change between Fluent versions 6 and 18.2?

  • Last Post 06 June 2019
  • Topic Is Solved
julia.hartig posted this 05 June 2019

I've noticed a confusing difference between the theory manual for the newest version of Fluent (18.2) and previous papers on/versions of Fluent regarding volume fraction in the governing equations for granular flow. The new theory manual seems to use volume fraction squared in all of the granular viscosity terms (shear, bulk, frictional and collisional), whereas the old manual uses a linear dependence (i.e. raised to the power of one). I've attached an example below:

From page 550 of the 18.2 ANSYS Fluent Theory Guide (see double appearance of the alpha_s term):

From Fluent 6 and Wachem paper "Derivation, Simulation and Validation of a Cohesive Particle Flow CFD Model" (first line of equation 28 below, epsilon is volume fraction here):


This alpha_s versus alpha_s^2 difference exists for all terms in the "new" expressions for granular viscosity. Am I missing something?  

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abenhadj posted this 06 June 2019

That was a problem in the documentation. The current implementation corresponds to the documentation.

Best regards,


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  • julia.hartig
julia.hartig posted this 06 June 2019

Ah I see. So just to be clear - the new documentation that lists volume fraction squared is the correct one?