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-   -   Cavitation in compressible flow (https://www.cfd-online.com/Forums/cfx/114962-cavitation-compressible-flow.html)

 soni7007 March 20, 2013 15:18

Cavitation in compressible flow

Hello,

I am simulating compressible flow in an injector with liquid phase.
When the flow converges, I define the vapor phase and turn ON the cavitation (Reyleigh-plesset), and set a saturation pressure.

I have repeated this whole simulation with Incompressible flow also.

Now, in an incompressible case, the flow rate before i turn on the cavitation is different from after. Also, the high negative pressures (globally and locally) that were seen before cavitation disappear and the lowest pressure is set to the saturation pressure. This looks good to me.

However, in the Compressible flow case, the flow rates before and after the cavitation are more or less the same. Also, the high negative pressure do not go away.
This is my problem. Can someone explain why the negative pressures are not adjusted to the saturation pressure in the case with compressible flow.
Also, any explanation for different behavior of the flow rates?

Both the solutions are converged.

 soni7007 March 20, 2013 15:22

Also,
Boundary conditions:
Inlet = Total Pressure
Outlet = Pressure

I get this warning when i turn on the cavitation during Compressible flow:

"This compressible multiphase simulation has more than 1 continuos phase and uses a total pressure boundary condition. The total static pressure conversion will be made assuming an incompressible equation of state"

What does this mean?

 ghorrocks March 20, 2013 17:32

Can you explain what you are doing? Also post an image. Are you injecting a liquid through an injector into an air stream? Is the air or liquid compressible? Why does it need to be compressible?

 mic March 29, 2013 13:06

Hi soni7007, a clearer explanation of your problem can help.
As far as my experience, I tried to simulate an injector for diesel engine application (compressible liquid) with Simerics. Also in cavitating situations, the results were good and physically reasonable.
:D

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