Mfix comes with DEM_Wall_HT cases

MFiX
#1

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There are two questions about this case:

  1. What does the code in the red box in the picture mean?
  2. What does the variable DES_QwFlux_AVG specifically indicate?
#2

Hi - it looks like you are running DEM_Wall_HT from the legacy_tutorials folder. Note that the “legacy” tutorials may need to be updated for various reasons (CGS units, etc). This one looks like it’s in SI units so I’m not 100% sure why it’s in the “legacy” folder but be careful with using this as an example.

The code at line 62 is checking to see if it is time to write the next VTK output file, as the comment at line 61 indicates.

And a comment in usr0.f says

! DES_QwFlux_Avg is a running average of the particle-wall heat flux

#3

I don’t understand what this average is for, why I can’t just use Reactionrates(ijk,1) to store DES_QW_COND

#4

You probably can. Looking at the code, the only place DES_QwFlux_AVG seems to be accessed is

usr1_des.f:            DEBUG_CG(:,M) =  DES_QwFlux_AVG(:,M)

so I think it was just probably put in there for debugging.

#5

Okay, thank you. Also want to ask you what the keyword vtk_debug (1,1) and DEBUG_CG (:,M) are. I didn’t find any information about them.

#6

You’re going to find a lot of variables in MFiX and I can’t explain the role of every one of them… search the codebase. These two are clearly intended for debugging.

VTK_DEBUG is a boolean which controls writing of the debug data stored in DEBUG_CG. These seem like they were intended for developer use and not end-users, which explains the lack of documentation.

IF(VTK_DEBUG(VTK_REGION,NN).AND.ALLOCATED(DEBUG_CG)) THEN
    WRITE(SUBN,*)NN
    VAR_NAME = 'DEBUG_'//ADJUSTL(SUBN)
    CALL WRITE_SCALAR_IN_VTU_BIN(VAR_NAME,DEBUG_CG(:,NN),PASS)
ENDIF
#7

Okay, thank you very much.