Mass fraction and reaction rate results

MFiX
#1

Case.zip (14.0 KB)

Hello

I have attached my DEM case files (project file+udf’s) and I have some problems to address.

1- I can’t know the arrangement of the reactions in the reaction rate array because I have two phases (homogeneous and Heterogeneous reactions). here is the numbering in the species.inc file:
image .
How can I match this with the reaction rate array which numbers them as 1,2,3,4,5,6,…etc?

2- In the output .csv file, I found that all the reaction rates=0.0 so why aren’t the reactions working?

3- Because the reactions aren’t working, definitely the mass fractions of all species= 0.0 except those in the initial conditions(N2 and H2O in my case). Is it necessary to put a small fraction of the products in the initial conditions?

Please check my files and help,
Thanks a lot.

– Mariam

#2

@cgw @onlyjus @jeff.dietiker

#3
  1. The arrangement is based on what you wrote in the usr_rates.f file:
    ! Save reaction rates for visualization
    IF(nrr>=R3) ReactionRates(IJK,R3) = RATES(R3)
    IF(nrr>=R4F) ReactionRates(IJK,R4F) = RATES(R4F)
    IF(nrr>=R4R) Reaction Rates(IJK,R4R) = RATES(R4R)

So here you are using the same numbering as in the species.inc. Index 1 is R3. index 2 is R4F and index 3 is R4R.

The array ReactionRate is for cell data, not particle data so you cannot use it as is in usr_rates_des.f.

2 and 3. I have not had a chance to run your case yet.

1 Like
#4

Thanks a lot @jeff.dietiker for your reply.

So, is there any way to save the reaction rates for the usr_rates_des.f file?
And to be more specific in point#2, the reaction named “devol” is not working. I need some help to know why it isn’t.

Thanks,
– Mariam

#6

Please see attached for an example on how to save the reaction rates in vtk files. A few notes:

  1. In usr_rates_des.f, I am saving rates both at the cell and particle level. I use ReactionRates for cell data and des_usr_var for the particle data. It is not necessary to do both.
  2. I used two vtp files, one for sand and one for biomass.
  3. You won’t see any reaction until biomass particles start entering the bed, this takes a while.
  4. I turned off the k-epsilon model. It was making the simulation fail, probably due to bad or undefined IC/BC values.
  5. I didn’t attempt to fix your reaction rates, but I can see issues in the way the species are used. For a gas phase species, first index is the cell, second index is the species, say X_g(IJK,H2O). For a solids species, first index is the particle, second index is the species, say DES_X_s(NP,Char). The devolatilization rate uses X_s(NP,pM,VM), which needs to be corrected.

vtk_rates.zip (19.2 KB)

1 Like
#7

Thank you very much @jeff.dietiker . I’m running the case now after the necessary corrections.

#9

Update: the case ran successfully until 5.96 sec when it showed this error: Unphysical field variables detected on one or more processes.

What can I do about this?

Thanks again,