[marsa27]

Hi,

I want to simulate the forming of a glass bottle

I would like to know if it possible use a degassing option for a multiphase VOF model (air and glass) to allow air to escape from the mold but not the glass?
In positive case how I can activate this option?
What kind of VOF model? Is enough a homogeneous VOF model?

Thanks

[Opaque]

If you want the phases to separate, i.e. different velocities at the same location, the model must be in-homogeneous.

Homogenous multiphase model --> shared field

[marsa27]

Originally Posted by Opaque

If you want the phases to separate, i.e. different velocities at the same location, the model must be in-homogeneous.

Homogenous multiphase model --> shared field

So in a dishomogeneous case is possible the degassification condition?
How I can active it?

[Opaque]

You have to check the documentation in detail. Specifically the outlet boundary condition for multiphase flow models.

From the documentation

2.5.1.9. Degassing Condition (Multiphase only)
Degassing boundary conditions are used to model a free surface from which dispersed bubbles are permitted to escape, but the liquid phase is not. They are useful for modeling flow in bubble columns.

When Degassing Boundary Condition is selected as the Flow Specification of an outlet, the continuous phase and any dispersed solid phases that may be present see this boundary as a free-slip wall and do not leave the domain. Dispersed fluid phases and Lagrange particles see this boundary as an outlet. However, the outlet pressure is not specified. Instead, a pressure distribution is computed on this fixed-position boundary, and can be interpreted as representing the weight of the surface height variations in the real flow.

Because the Degassing Boundary Condition does not specify a pressure value, a fixed pressure reference point will be set automatically for a domain with an incompressible flow with degassing boundaries, but no pressure boundaries.

[Gert-Jan]

In Pre, just define an outlet, there select the option 'Degassing Condition'.

[damlayilm]

Hello everyone. I am trying to analyze aeration tank simulation. In order to convert the water surface to degassing condition, first I changed the surface that I selected as outlet to degassing from the type tab, but since outlet is not visible in the analysis, I get an error saying that it is not converged. What is the reason for this? Also, in some studies, I see that both degassing (for air) and symmetry (velocity) are entered for the same surface (aeration tank surface), but when I name the same surface in two different ways, it does not accept it. Can anyone help?

Inlet- diffusers
outlet (degassing condition) - free surfcae

[ghorrocks]

Please post your output file and an image of what you are modelling.

[damlayilm]

Hello. There is a rectangular 'inlet' that provides air outlet from the bottom of the tank. The water surface of the tank is 'outlet'. All the remaining parts are defined as wall. In the setup section, I change the type of 'outlet' to degassing, but it does not see the outlet in the initialization and the continuity curve goes up to 10^12 and diverges. By the way, even if I leave the outlet as pressure outlet, the continuity diverges and the analysis does not give any results. I don't know where I am making the mistake. My mesh quality is within the required range. Are my boundary conditions wrong? There is a rectangular air sprayer from the tank bottom and this is the inlet. The outlet is the surface of the water. (There is already water in my system).

[ghorrocks]

Please attach your output file.

What do you mean by "but it does not see the outlet in the initialization"? What does not "see" it? During initialisation of what?

[damlayilm]

There is a message like that. When i covert outlet to degassing 'This case has only inlets'

[ghorrocks]

What software are you using?

[damlayilm]

ansys fluent 2019 r3

[ghorrocks]

Try the fluent forum. This is the CFX forum.