[dinhanh]

123.png

124.pngHi,
I am doing simple cavitation simulation in the orifice nozzle by using the model of Nurick which is similar to fluent cavitation tutorial.
so I used the axisymmetric for this calculation. But the results are very different to Nurick's experiment. I also tried to run same condition with fluent tutorial file. The result is also different.
Fluent report the volume flow rate is about 0.36m3/s which true result is about 10e-5m3/s.

The flies below are the geometry grid, calculation condition and model grid. You also can find in the paper: "Mathematical Basis and Validation of the Full Cavitation Model" of Singhal


(The geometry are outlet: d=8mm, inlet D=2.88d, nozzle length L=5d.)

Do you have same problem? How to fix this problem?
many thank!

[dinhanh]

ghost82,
I saw you have experience about cavitation. Could you give comment?

[ghost82]

Hi Anh,
your problem should be related to boundary conditions and/or solution convergence.
I tried to run a simulation with steam/water properties at 20 degrees, 500000 Pa inlet pressure and 95000 Pa outlet pressure (absolute) and I obtained a flow near 0.99 kg/s, which in my experience is correct.
Flow rates depend obviously on pressure inlet/outlet.

I saw that you have at inlet 2 velocity inlet boundary conditions: what velocity did you set?
I suggest to change the inlet bc to pressure inlet.
With 500000 Pa inlet pressure I have a mean velocity at inlet near 2.4 m/s.

Remember to set properties of vapor at a pressure equal to the vapor pressure at the operative temperature (for example, if you have water flowing at 20 degrees, then vapor pressure will be 2340 Pa (absolute) and corresponding density will be 0.017 kg/m3).

I suggest also to use the coupled scheme.

Daniele

[dinhanh]

Thank you very much for your suggestion, ghost82.
I solved my problem.