mole fraction and mass fraction?

Parmar_123Parmar_123 Member Posts: 1

hello team members

I am running simulation(600 seconds) regarding diffusion of hydrogen gas in a cuboid container(no openings). Initially, air is there in the container. After, I am adding hydrogen with a certain value of mass flow rate in Kg/Sec for 600 seconds. The method I am adopting is:

  1. pressure based, absolute, transient, gravity(y=9.81m/s2)
  2. energy equation(ON), k-epsilon, species transport[(ON), volumetric(On), inlet diffusion(ON), diffusion energy source(ON), finite rate eddy dissipation(ON)]
  3. boundary conditions : mass flow inlet, direction specification method=normal to boundary, specification method=intensity and hydraulic diameter, species(H2=1 value)
  4. scheme = PISO, 2nd order for <kinetic energy, transient formulation, dissipation ratio>
  5. hybrid initialization, time step size= 0.1
  6. data file quantities=mass fraction of H2, mole fraction of H2 and many more.

During the post processing part, I am interested in contours of mole fraction at a particular plane but mole fraction contours are showing nothing at that plane. While for mass fraction, I am getting results. Here is the picture, picture 1 for mass fraction and picture 2 for mole fraction:

I am more interested in finding out the contours of mole fraction.

please help

with regards



  • KremellaKremella Posts: 3,196Admin


    Are you able to see these results on Fluent? Can you try and post-process them directly on Fluent and let us know your finding.


  • RobRob UKPosts: 12,322Forum Coordinator

    Fluent may not export that data in the files as it's calculated on the fly in the solver when we post process. As CFD Post doesn't know much about the materials it can't then calculate the value.

  • Parmar_123Parmar_123 Posts: 6Member

    thank you sir

    these results i have calculated in post processing part by loading case and data files.

  • Parmar_123Parmar_123 Posts: 6Member
    edited January 10

    actually sir i am validating my model with a research paper.

    this is the research paper.

    I have created same geometry using ANSYS ICEM software and make mesh file(4lakh hexahedral elements) ready for fluent in the same software(ICEM).

    Then I make FLUENT to read mesh and prepared the setup in the FLUENT. (In the top I mentioned the steps during setting up my model).

    Firstly, I want to know is there any thing left during the setting up model according to the paper?

    After completion of simulation I am plotting graphs for Hc=0.12m an also the contours as mentioned in research paper.

    (given below are the graphs and contours in the research paper)

    but I neither getting plots nor contours same or little bit closer.

    I need urgent guidance in this situation.

    It will be much more helpful if We can connect through email.

    Thank You

  • RobRob UKPosts: 12,322Forum Coordinator

    I've removed the email address, all comments from staff must remain in the public domain due to the export rules we're required to obey. I'm also not permitted to open attachments for the same reason.

    As I don't know what you're seeing I can't comment. However the plots look to be a concentration at a set position at 400s? For a 400s simulation you'll need a lot of time steps (we need to resolve the flow field) so I'd check if each time step has converged. The 400k cell count may or may not be sufficient: if the domain is 3x12m then it's likely too coarse if uniform.

  • Parmar_123Parmar_123 Posts: 6Member

    thanks sir

    Is there some way or platform to discuss this problem with you?

    Because I am not able to share some all details.

  • KremellaKremella Posts: 3,196Admin

    Unfortunately, not! Please see if you are able to replicate the issue on a simpler canonical problem and may be you can provide some more info on that?

  • DrAmineDrAmine GermanyPosts: 8,012Forum Coordinator

    Do you see the mole fractions in Fluent? How are you exporting results from Fluent to CFD-Post? Are you using CFD-Post Compatible files there?

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