(Uniform particle size distribution) Why I have fractional #parcels/cell in my injection surface?

- January 9, 2020 at 5:51 am
  
  ai0013
  Subscriber
  
  Although I have specified uniform particle size distribution for my DPM injection, the contours, as well as the particle track reports, show that 0.803 parcels/cell are injected. My surface has 336 mesh cells. Any explanation would be really appreciated
- January 9, 2020 at 5:56 am
  
  DrAmine
  Ansys Employee
  
  In Fluent we track particle packets representative of particles called parcels where the number of particles per parcel might vary depending on other model settings.
  
  Is this enough?
- January 10, 2020 at 12:47 am
  
  ai0013
  Subscriber
  
  Well, when fluent displays the DPM iteration in the console, it says 336 parcels are injected (because I have 336 cell elements). This might correspond to 1 parcel per cell, but fluent somehow says I have 0.803 parcels per cell at the injection surface. I want to know why I have fractional parcels.
- January 10, 2020 at 11:37 am
  
  DrAmine
  Ansys Employee
  
  Are you running steady or unsteady particle tracking? Can you show what are you displaying?
- January 14, 2020 at 1:28 am
  
  ai0013
  Subscriber
  
  This is unsteady particle tracking, uniform particle size distribution,
  
  I am injecting particles with the 'Scale Flow by Face Area' option ON. Here you can see the contours for particles in cell, As well as my manual calculation (cells in orange). I used m_dot_particle = #particles/sec * mass_particle (for each cell) And from the input total mass flow rate (in the surface injection) and cell area/surface area ratio I solved for #particles/sec and then multiplied this by the injection time step. I understand how Fluent works, but I still dont get why when I display the number of parcels per cell, I have 0.803 parcels per cell at the injection surface, even though the console says that 336 parcels are injected in a mesh that has 336 cells.
  
  Please correct my idea if it is wrong. For the cells in red, each parcel contain 53 particles, for the cells in orange 47, and so on... ? Is this right? So why I have fractional number of parcels in Fluent?
- January 14, 2020 at 5:54 am
  
  DrAmine
  Ansys Employee
  
  Please sample along the inlet for one step or list the injection it is better than Using the Eulerian variables. The latter are averaged quantities and depend on residence time in a cell.
  If you plot particle trajectories you might control number of particles per parcel. A