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 usker March 23, 2007 01:10

Spray Injection

Anyone knows what is the definition of number of parcels? In Lagrangian Multi-Phase-> Spray Injection with Atomization there is Number of Parcels/Injector/s (Parcel Injection Rate). How to determine correct parcel injection rate? If I change the parcel injection rate I get completely different results.

Thanks

 Richard March 23, 2007 04:48

Re: Spray Injection

The number of parcels in Lagrangian is analogous to the number of cells: it doesn't have any relationship with anything physical, it's just how you choose to discretize the problem in order to make it solvable. As with cells, changing the number of parcels could change your solution, in fact it probably will. Hopefully as you increase the number of parcels (or cells) the Lagrangian (or Eulerian) solution becomes more accurate, until it becomes insensitive to further refinements - though whether you can ever afford to refine this far is another question.

 usker April 6, 2007 00:41

Re: Spray Injection

Richard, thank you for your previous clear explanation. Let's assume that my injector nozzle diameter is 0.0001m, I specify appropriate flow rate, number of parcels and so on, I run Star and get results. In pos-processing I select "Plot Droplets/Particle Tracks ->Droplet Plot Options->Droplet Radius->Diameter->0.0001. Then I want to plot particles distrubution with the size from 0.0001m to whatever smallest size it can show me. When I insert the size of my nozzle(0.0001m) in "Droplet Radius" as a "Diameter" i cannot see any particles on the screen, but if I increase the size to 0.1 and higher I can see particle distribution. But the problem is that how I can get right fuel liquid length. Because If I play around changing the size in "Droplet Radius" the total spray length also changes. In other words, if I increse the size of droplets, total spray length increases, and vice versa.