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-   -   Simplified VOF Model (http://www.cfd-online.com/Forums/fluent/77030-simplified-vof-model.html)

gulbenkian June 10, 2010 15:57

Simplified VOF Model
 
Hello

I am trying to solve a transient simplified model in 2D. Air is flowing from a source at 200000 Pa and get into contact with a pool of water of 2mm X 4mm before expands to atmospheric conditions see Figure 1.

http://img717.imageshack.us/img717/8293/figure1e.png

I want to see the deformation of the water (droplet formation if any) due to the air flow. I am having problems to get convergence in the model. I am using a VOF model using air as primary phase and the water as secondary phase. As boundary conditions I am using a pressure inlet and pressure oulet conditions. I am patching the water at the beginning. I have used a k-e model and a simplified laminar model for the air and a time step size of 0.0001, however, after I begin the iterative process, it quickly diverge.

I highly appreciate if someone can give me some ideas. :)

Thanks in advance

pranab_jha June 10, 2010 16:52

Hi,
What error message does Fluent give you?
I am also using VOF and facing some issues with divergence. I am modeling two-phase flow in pipe. I got the error msg: "divergence detected in AMG solver: pressure correction" when I initialized the whole pipe domain with VF =1 or even with VF = 0.5. But for low phase velocities, I was able to 'avoid' divergence by lowering the relaxation factors for pressure from 1 to 0.5. But I am not able to get around it for higher velocities (air and water ~ 1.5 m/s, pipe dia = 50 mm) by lowering the value further.
I guess you can try it. Maybe it works for you. If you come across any useful tip, do let me know.
Thanks,
Pranab


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