Fluids

Fluids

Fluent: Rosin-Rammler PSD – Spread parameter is altered by fluent!

    • ai0013
      Subscriber

      Hello,


       


      I noticed my simulation is not using my specified spread parameter (3.5), rather is using 2.84!!!  Why is this happening??


      I checked this with a manual calculation of the RR distribution based on particle sampling over a cross-sectional floating surface, and with the dpm summary report!! 


      If someone knows how fluent deviates from my specified value, please let me know!

    • DrAmine
      Ansys Employee
      How did you get the RR? Also to get the theoretical value one would need zo have a lot of parcels/diameters. Where are you sampling?
    • ai0013
      Subscriber

      Thanks for your kind reply


       


      I did a particle sampling for my combusting particles over a cross-sectional floating surface in my injector (where no reactions are taking place yet). I ran it for approx 2,000 particle injection time steps and then post-processed the data in the histogram tool. I weighted the data by parcel-mass and divided the frequency distribution by the bin size. Then compared this to the derivative (PDF) of the analytical RR. 


       


      Blue line: my pre-defined (analytics)l PDF RR (n=3.5)


      Red line: fluent (analytical) PDF RR based on reported spread parameter (n=2.84) (summary report)


      Squares: fluent (numerical) PDF RR based on particle sampling



      From here I see Fluent is deviating my spread parameter, so don't know what is happening. Should I sample for a longer time?

    • ai0013
      Subscriber

      Does anyone in the community has noticed something similar to the above problem? Thanks

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