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-   -   The LESModel for the family of LESmultiphase solvers (http://www.cfd-online.com/Forums/openfoam-bugs/62417-lesmodel-family-lesmultiphase-solvers.html)

 ngj September 23, 2008 16:12

Description: I have dug into

Description:
I have dug into the source behind the turbulence modeling for the family of LES-multiphase solvers. As I consider the general equation for turbulent kinetic energy, it includes rho, but in neither of the LES-multiphase solvers rho is part of the k-equations (I have only checked oneEqnEddy), but all uses incompressible formulation - even compressibleLesInterFoam.

I believe that the turbulence equation for multiphase flows should take the density into consideration, thus a bug-fix would be to replace it with compressible flow equations.

Solver/Application:
The family of LES-multiphase solvers:
- interPhaseChangeFoam
- lesInterFoam
- compressibleLesInterFoam
- lesCavitatingFoam

Source file:
createFields.H in the above mentioned solvers.

Testcase:
None

Platform:
All

Version:
1.5

Notes:

 henry September 23, 2008 16:39

I developed the current approa

I developed the current approach to avoid spurious generation of turbulence at the interface where there may be a VERY large density gradient not associated with compressibility effects. To use compressible formulations of turbulence it would be better to use a fully two-phase formulation and solve for the momentum and turbulence properties of both phases, that way avoiding the issue of the density gradient at the interface.

H

 ngj September 23, 2008 17:15

Hi Henry Thanks for the rap

Hi Henry

Thanks for the rapid answer.

I am curious, what do you mean by "fully two-phase formulation", because the momentum and turbulence equations are solved for both phases in e.g. lesInterFoam.

Do you mean, that one should solve for the two phases separately with a clean interface?

Thanks,

Niels

 henry September 23, 2008 17:40

I mean solve momentum and turb

I mean solve momentum and turbulence equations for both phases, i.e. two momentum equations and two sets of turbulence equations. The current family of VoF solvers use a "mixture" approach in which a single momentum equation and single set of turbulence equations are solved.

H

 ngj September 23, 2008 18:15

Thanks, Niels

Thanks,

Niels

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