13 Replies Latest reply on Jan 20, 2015 11:41 AM by Chris Michalski

    preventing particles from being lost as embedded

    Chris Michalski

      In running Flow Simulation Particle Studies on a project I keep having all of my particles lost because of high velocity normal impact on solids.  Out of 300 particles traced I might get 1 or 2 successfully following the flow trajectories.  Changing restitution coefficients doesn't help.

       

      The only thing I'm really concerned about in this particular case is the temperature lag of the particles versus the fluid, it is a confined flow path with no chance to settle.

       

      I found that reducing particle diameter lets the particles continue on through the model.  I'm assuming this is because the reduced momentum at impact doesn't push them so far into the solid that Flow loses track of them.

       

      I'm not 100% sure what all Flow calculates as far as Fluid/Particle interactions in a particle study (and I'm off contract so I can't look at the KB to investigate) so I'm looking for feedback.

       

      I copied my stock material and then doubled the specific heat and reduced my specified particle diameter (to 40%) such that the heat capacity per particle (J/K) is still accurate.  I didn't change the thermal conductivity or density of the particle material. 

       

      Am I correct in believing that Flow considers the particle to have a uniform temperature?  Such that the conductivity of particles doesn't matter?  Or does it only display the average temperature while calculating for an internal gradient?

      Does it utilize the particle surface in its calculation of heat transfer to the particle?  (If so reducing my particle diameter should be a conservative approach as it reduces the area so reality would be a smaller delta T).

       

      Thoughts??  What other techniques have people found for preventing particles from getting lost that maintain thermal properties?