Fluids

Fluids

Incomplete Particle Tracking in Fluent

    • SudharsanSadagopan
      Subscriber

      Hi,

      I am trying to simulate the flow of particle laden fluid in a microchannel. During postprocessing, certain particle tracks are reported as incomplete. I tried increasing my Max Number of Steps from 50,000 to 500,000 but there is no change in the result. This is a laminar, steady state simulation. I am using three particle sizes (20microns, 5 microns and 1 micron). For the particle size of 5microns and 1micron, the number of incomplete particle trajectories drastically decreases and most particles travel the full desired length of the channel. The issue of incomplete particle trajectory arises only for the 20micron particle. Can you please suggest what I could do differently to compute the full trajectory for the 20micron particles? Thanks

    • Surya Deb
      Ansys Employee
      Hello, nFor the larger particle, what is the Stokes number coming out to be? is the particle settling down somehow?nCan you plot the particle trajectory for the 20 micron particles to see what is happening in the flow domain?nRegards,nSuryan
    • SudharsanSadagopan
      Subscriber
      Hi,nThanks for the reply. To check if the particles are settling down due to lower flowrates, I increased the inlet velocity and sure enough the particles are travelling further distance along the channel. This leads me to believe that the particles might have settled down in the original simulation. nBut now, the 20 micron particles are entering and traversing through channels that are 5 microns high. I observed something similar when 5micron particles entered a channel that was 0.5microns high. Is this a numerical error in Fluent and if so can you kindly suggest how it could be fixed?nThanksnn
    • Rob
      Ansys Employee
      It's not an error, the DPM model works on a point mass which is covered in the theory guide: it's also why the particles need to be smaller than the cells. So, yes a 1cm particle will fit through a 0.5micron hole. If you need to account for the diameter relative to channel size you may want to look at the macro particle model. n
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