[Stabum]

Hello to everybody,
I'm trying to simulate a centrifugal pump impeller in order to underline the cavitation phenomena. Before starting this simulation I read (and understood, I hope) the tutorial 28, dealing with a topic VERY similar to what I wanted to simulate.
I have firstly simulated my own impeller using "Liquid Water" as substance and got an excellent convergence (100000 Pa total pressure in stn frame at inlet and mass flow rate at outlet). I obtained (with 1E-6 RMS residuals) an overall efficency = 96% and a head = 20m.
Then I added a second substance (Water Vapour), activated the homogeneus model, Fluid Pair Model with Cavitation Option (Rayleigh Plasset Option) and I finally adjusted the Saturation Pressure (3570 Pa). (All the datails of my settings can be found in the tutorial n.28). Obviously the boundary conditions at the inlet (100000 Pa total pressure stn frame), and outlet (bulk mass flow rate), are the same of the previous simulation.
I used the results of the previous converged simulation (with liquid water as the only substance) as initial guess, but the bi-phasic simulation (despite the inlet pressure = 100000 Pa, which should mean that there's no vapour) cannot converge: Head reaches a value of 800m (when it should be 20/20.5 m), before the residuals start a asymptotic behavior.


I hope I have been able to describe what I've done. Please ask me to clarify better if needed. Please help me to find a strategy to obtain a solution which could have a physical sense. Thanks so much, guys

[ghorrocks]

Have you had a look at the results file? That should show you what the flow field looks like. If it is spuriously generating cavitation then at least you will know where it is coming from.

[ragab]

i would like to understand how could I activate the mass flow outlet when i simulate a two phase flow