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-   -   Problem: hollow cone spray with TAB model. (http://www.cfd-online.com/Forums/openfoam/65930-problem-hollow-cone-spray-tab-model.html)

chenhu July 1, 2009 08:33

Problem: hollow cone spray with TAB model.
 
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I am trying to simulate hollow cone spray with TAB breakup model, but the result is very strange. There is a finger in the spray. When I switch off the TAB model, it looks normal.
I compared the OpenFOAM TAB implementation with KIVA. The only difference is that the droplet velocity and direction is not updated after breakup in the TAB.C file. I don't know if this is the reason for the strange droplet distribution.
Can anybody tell me where the droplet velocity and direction is updated in the OpenFOAM?
What might be the cause for this problem?

This is the droplet distribution with TAB breakup.
http://lh3.ggpht.com/_OYtXHb5wD_0/Sk...c/s640/tab.jpg

This is the droplet distribution without TAB breakup.
http://lh3.ggpht.com/_OYtXHb5wD_0/Sk.../s640/NoBu.jpg

schmidt_d July 3, 2009 11:25

Chenhu,
It looks to me like the finger is comprised of very small droplets formed by the TAB model's predicted breakup. Gas flow in these types of spray is from the outside towards the centerline of the spray. These small droplets are convected to the centerline while the larger droplets continue on their ballistic trajectory. The prediction of very small droplets is a common criticism of the TAB model, though I still use it myself.
-David


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