Fluids

Fluids

DDPM – error

    • Nara22
      Subscriber

      Hello everyone, 

      I am relatively new to ANSYS and would like to receive help with my simulation.

      I am simulating the two-phase solid particles - gas in an Eulerian-Lagrangian frame using DDPM and a vertical pipe. I activated the multiphase model and thus defined my solid phase and my gas phase. Within the solid phase, activate the 'Granular' option in addition to selecting its properties. 

      The characteristics of my solid particles are the following:

      Diameter: 0.0002m // Velocity_inlet: 0.81 m/s // Total flow rate: 0.03391665

      I am using this DDPM option: 

      My residuals are:

      In the end, I got two issues:

      1) I got an error in the results:

      2) I got this trajectory calculation: trajectory calculations are not completed

      I would appreciate any recommendations on those errors.

    • Rob
      Ansys Employee

      The first problem is a missing setting somewhere in the model. If you've been turning things on and off you may have caused a glitch in the set up. In that case you may have to start again if you can't find it. 

      The incomplete message means you're not tracking particles long enough: they're running out of integration steps before leaving the domain. However, the continuity equation is very definitely not happy so I suspect incomplete particles are the least of your problems. 

      Why are you using DDPM over DPM or Eulerian multiphase model? DDPM isn't used that commonly so I wonder if you need it. 

    • Nara22
      Subscriber

      Hello Rob, I am using DDPM because part of my research is track the particles in a Lagrangian framework including the particle volume fraction in it, and because the volume fraction of discrete phase is more than 10%.

      I would appreciate any aditional comment to this matter.

      Thank you.

    • Rob
      Ansys Employee

      You'll need to be more specific. Multiphase is a mix of understanding the application and required outcome AND how then to best model it. I've modelled cyclones with DPM, Ansys Rocky (DEM) and Eulerian: all three are correct approaches but each was to capture a different requirement. 

      Pictures only, as staff I'm not permitted to open/download anything or follow links other than to public sites (and only if we recognise it!). 

    • Nara22
      Subscriber

      Hello Rob, thank you for reply

      I am choosing the DDPM model, for the following:

      - I would like to evaluate the trajectory of the particles

      - Because I want to handle higher volume fraction

      - The study is about a gas-solid flow in riser, including particle-particle interaction

      I am trying to replicate the study of Bolio et al. in Ansys fluent, this study has the following characteristics (steady, fully-developed vertical pipe flow):

      I am looking for compare my results with their results:

      According to what I mentioned before, I considered modeling in DDPM, if I'm wrong please correct me or please give me some suggestion.

      Thank you.

    • Rob
      Ansys Employee

      I would tend to use Eulerian for risers, not least because of the parcel loading. Or, more recently, I'd use Ansys Rocky as it's a DEM code: Fluent handles the flow and Rocky the particles. 

      If you use 22R2 the DDPM model has had some work done to help with higher volume fractions. I also suggest increasing the max number of steps on the DPM panel. If you're losing that many parcels as incomplete you have a lot of unaccounted mass to worry about: I assume you are tracking the particles as transient? 

    • Nara22
      Subscriber

      Hello Rob, unfortunately, I don't have the Ansys Rocky software, and the version we handle is 22R1.
      Yes, I am tracking the particles as transient. Any comment about this option?
      Now I am working with the option to increase the maximum number of steps; I have already started the calculation, and so far, it is tracking the particles.


      Thank you for your comments.

    • Rob
      Ansys Employee

      You'll be injecting 500 parcels every time step. So, the number tracked will increase until the system reaches equilibrium. Hopefully this happens before you run out of compute resource. 

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