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Cavitation Simulation of low mach flow over 2D airfoil

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Old   February 23, 2012, 09:30
Default Cavitation Simulation of low mach flow over 2D airfoil
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Hello everyone.

I am currently having some trouble in the simulation of a low mach cavitating flow past a 2D NACA0015 profile.
I am using the full cavitation model in the ANSYS 13 fluent (Schnerr-Sauer).
Unfortunately, i am encountering some difficulties as to make the simulation converge.
Perhaps am I using a wrong overall methodology? I started with a laminar, monophasic case. once it converged, I activated the mixture model, and then the cavitation model in RNG k-e. (my intent is to implement the Singhal cavitation model once i've succeded in using the fluent cavitating model)

Arriving at this stage, i observe a psoeudo-periodic "aberration" in the residuals, as linked with this post.

Throughout the calculation, i observe alpha contours which alternatively seem accurate, of absurd. (as shown in the screens linked)

My boundary conditions are as follow :
Inlet : velocity=18m/s pressure=74
Outlet : pressure=74175Pa

I dont know what i am doiing wrong. should i decrese the outlet pressure, starting with a higher one? shoule i adjust the under relaxation constants? should my whole simulation steps be revised?

i thank you in advance for the help you might give me.

Regards : Harkot.

P.S : I am adding a mesh screen just in case.
Attached Images
File Type: jpg NACA12_REFINE_MONO__75_OK_READY.jpg (57.0 KB, 42 views)
File Type: jpg NACA12_REFINE_MONO__75_OK_READY_alpha.jpg (62.4 KB, 40 views)
File Type: jpg mesh.jpg (96.9 KB, 35 views)
File Type: jpg mesh_zoom.jpg (96.2 KB, 27 views)
File Type: jpg mesh_bigzoom.jpg (98.5 KB, 28 views)
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Old   March 6, 2012, 06:22
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Old   March 24, 2012, 14:30
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Hello, Harkot.

In the similar case I have something strange with residuals too. When I use the Singhal model, residuals of vapor transport equation are constantly on zero level, but the solution have good convergence.
If solution in your problem haven't any aberration, I think there is nothing to worry about.
But if there is instability in solution, it may indicates that flow is unsteady. It confirms with the value of Cavitation number, in your case it is rather low approximately 0.45 ( if you use the default value of vaporisation pressure 3540Pa and water density) .
I have not so much experience in modeling cavitation, I can solve my problem only with Singhal model and have divergence in AMG solver if I trying to use Zwart or Schnerr model. Did you ever get the solution with this models?

Regards : Junior.
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Old   October 1, 2013, 11:04
Default cavitation steps
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Please I am simulating cavitation of 5 bladed marine propeller using Ansys Fluent,

I am new in simulating multiphase flow, and i need if it is possible steps to simulate cavitation using Fluent

Best regards

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2d airfoil, cavitation, low mach, naca 0015

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