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-   -   VOF with a moving mesh (http://www.cfd-online.com/Forums/fluent/49896-vof-moving-mesh.html)

Jeremie November 25, 2008 16:43

VOF with a moving mesh
 
Hello, I'm working on a fuel jet (300-500pph) impacting a rotating flat disk or cup (20000-40000rpm, D=4cm). The thickness and the velocity of the liquid film developing on the rotating disk are of interest. The injection is stationnary, only the disk is moving. I have made several researches on the Internet and in the scientific literature, in order to know which model(s) I have to use in Fluent. It turns out that the VOF Model is ideal to track the liquid-gas interface (and thus the liquid thickness). Then I chose a moving mesh to simulate the rotation of the disk. It seems possible to use both models (VOF and Moving Mesh) in the same time. And the first results were not so bad, but now I want more precise solutions, so I created a boundary layer on the surface of the disk. The point is that the courant number increases when the fuel jet enters the smallest cells of the mesh (closed to the disk), and the computation stops.

I guess the problem comes from the minimum cell size and/or the time step. But it would be very helpful if somebody has an experience with this kind of problems (VOF + Moving Mesh). Is it possible to get accurate solutions using these models together? And then, what are the key parameters? Any comments can help.

Thank you very much Regards

Here some information about my computations: - Unsteady pressure-based solver - Explicit VOF Scheme - Realizable k-ε model with enhanced wall treatment - Pressure-Velocity Coupling : PISO - Discretization : Pressure : PRESTO! - Time Step : 5e-6 s - Max iterations per time step : 50

Anna November 26, 2008 09:55

Re: VOF with a moving mesh
 
I had stability issues whilst using the VOF model as well. Try enabling the Rhie-Chow face flux interpolation. This is done through the main window by typing:

solve/set/numerics keep the other variables the same and when it comes to Rhie-Chow select y rather than n. You may also want to reduce you URFs to about 0.7.

Hope that helps. Anna


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