Choosing a value for K-epsilon model and issuee with allocation of those values in DEM modeling

[sayyamchopra]

Hello @jeff.dietiker @cgw ,
I have a very important question to ask working with DEM modeling to use the K-Epsilon model. I have my simulation setup ready for chemical looping but I have two specific concerns.

1. Once i select K-epsilon as a turbulent model, I need to assign a. K-E turbulent kinetic energy, b.K-e turbulent dissipation, and c. maximum turbulent viscosity. Can you see my setup and give me a range or a value that i can select for this modeling? I know these values are variable but i just needed a range to start with.

2. Now, i am confused as to where to assign these values. The setup asks to assign these values in initial as well as boundary conditions. also, are these values the same for fluids as well as solids?

I would be glad if you could clarify this concern of mine. I have completed my data collection without turbulent modeling but now i plan to use turbulent modeling.

A help or suggestion is highly needed.
thanks in advance

simulation3.5mm25secvar_velocity.mfx (16.2 KB)
geometry_0003.stl (719.6 KB)
geometry_0001.stl (8.7 KB)
geometry.stl (719.6 KB)
chemicalloopfinal.stl (431.7 KB)
BOX1_FACETS_IGNORED.stl (25 Bytes)
SIMULATION3.5MM25SECVAR_VELOCITY.msh (16.9 MB)

[cgw]

Hi Sayyam -

For the max turbulent velocity, stick with the default unless you have a particular reason to change it:

Initial conditions are imposed at t=0, while boundary conditions are imposed all throughout the duration of the simulation. This is why there are two sets of inputs. This goes for everything in the ICs (Initial conditions) and BCs (Boundary conditions) setup panes:

The turbulence paramaters apply only to the fluid phase, which is why they are present when the fluid sub-tab is selected but are not shown for the solids phase:

They can be different for each BC or IC region (selected row in the table at top).

I cannot provide values for these parameters - this depends very much on your simulation. Looking through the MFiX tutorials there do not seem to be any which use the k-epsilon model. One of our old tests FLD08 uses the following values:

  IC_K_TURB_G(1) = 0.047    ! (m2/s2)
  IC_E_TURB_G(1) = 0.213    ! (m2/s3)
  BC_K_TURB_G(1) = 0.047     ! (m2/s2)
  BC_E_TURB_G(1) = 0.213     ! (m2/s3)

In this case the same values are used in the initial condition as for the boundary condition. I do not expect these values to be correct for your case but they could be a starting point.

[sayyamchopra]

Thank you @cgw for this valuable suggestion.