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-   -   High temperature problems in cavitation analysis (http://www.cfd-online.com/Forums/star-ccm/108321-high-temperature-problems-cavitation-analysis.html)

ecto October 19, 2012 09:20

High temperature problems in cavitation analysis
 
Hi everybody!
I'm using Starccm+ 7.04 to simulate isoctane flowing through a cylindrical pipe in a nozzle of an automotive GDI injector, in particular I have to investigate the occurring cavitation. The pipe is 0.14mm in diameter and 0.3 mm in lenght. Pressure inlet is 120bar.
I set up models with 600'000 and 3'000'000 poly cells, with Standard k-e low y+. In both of them I can see that, as soon as I activate cavitation option, temperatures in the nozzle go crazy, raising the maximum value I set, that's 700K. Pressure, velocity and flow rate are consistent with experimental values.

Maybe someone has had similar experience.
Can someone help me?
Many thanks

ecto October 19, 2012 09:22

Ah, I forgot to say that I'm using Eulerian multiphase VOF model.

sieginc. October 19, 2012 14:38

http://imageshack.us/a/img571/2903/hightemps.jpg

I've had a similar thing happen to me, and it looked like that. Unrealistic spikes in strange places as soon as I started the simulation. Initially I used the polyhedral mesher, but then switched to the trimmer and that solved the problem. My guess is that the poly mesher was not able to capture some of the geometry causing my solution to diverge.

ecto October 19, 2012 15:03

Thanks for the help, I will try with trim mesh.
Regards

ecto October 30, 2012 08:31

I confirm that switching to trim mesh and to k-epsilon two layer all y+ risolved the problem of high T.


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