DPM modelling

MilhmMilhm Member Posts: 19

Hi,

what is the best value for number of tries in discrete random walk model when simulating steady state injection?

Comments

  • RobRob UKForum Coordinator Posts: 8,371

    The purpose of the option is to allow the parcels to disperse due to turbulence. If you have a large number of parcels from the injection then fewer tries may be needed, if you have few parcels from the injection then you need more tries. There is also an upper limit on the number of tries based on your hardware. Somewhere between 1 and 1000 is fairly common, 10-100 may be a good starting point.

  • MilhmMilhm Member Posts: 19

    i have 200 number of streams and my droplets have constant diameter of 20 micron.Which number of tries is good for it?

  • RobRob UKForum Coordinator Posts: 8,371

    How big is the domain, are particles passing through or are you seeing incomplete tracks?

  • MilhmMilhm Member Posts: 19

    domain is a pipe with diameter of 260mm and lenght of 4 m.particles are sprayed into the pipe.

    no i do not see incomplete tracks.

  • RobRob UKForum Coordinator Posts: 8,371

    In which case keep increasing the number of tries until whatever you're monitoring stops changing or the computer falls over. Save before plotting particle trajectories! My earlier comment about 10-100 tries being a good starting point stands.

  • MilhmMilhm Member Posts: 19

    trajectories in steady injection should be arranged and regular or Irregular and disordered?

    are these trajectories acceptable?

  • RobRob UKForum Coordinator Posts: 8,371

    The particles will follow the flow to varying levels depending on diameter and relative material density. The result looks like what I'd expect to see from a DPM track, whether they're correct is for you to judge based on the flow.

  • MilhmMilhm Member Posts: 19

    the main flow is air and droplets are water.

    i have another question.What are good values for step length factor and length scale?

    how they should be selected for a simulation?

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