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Jeggi December 4, 2014 09:12

Two-phase critical flow and shock modelling of nozzle

I am trying to use the experiments from an article in order to validate two-phase critical flow and shocks for water-air in STAR-CCM+. (Sadly, the article is behind a payment wall).

The geometry and boundary conditions can be seen in the image below:

The air inlet has a pressure of 6 bar and the outlet has pressure of 2.44 bar. The mass flow rate of water is fixed at 498 kg/h.

I am using the Eulerian multiphase segregated flow solver with both water and air set to be compressible. I have been able to obtain reasonable results for the critical mass flow rate, but it has not be the case for the pressure profile along the nozzle as STAR-CCM+ does seem to over-predict the shock.
As of now, I have been using the S-gamma model in order to describe the interaction length scale for the two-phases by the Sauter Mean Diameter as recommended in the user guide (for droplets/bobbles). My issue is though that I don’t know if this model is applicable for my case?

It is also possible to set the interaction length scale to a constant, but I am hoping to avoid this as it will make it troublesome to transfer the validation case to a real case. Or is there a way to calculate the interaction length scale base on physical properties ?

Any help would be greatly appreciated.

- Jeggi

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