[oliveira1820]

I have a 3 per 3 cm container with gaseous water and liquid water (85%) that constantly suffer phase change due to a 1000 W energy source, and I have air (15%)inside too. What is a good prediciton to the air (dispersed fluid) average bubble diameter?

[ghorrocks]

You will need to explain what you are intending more completely.

What is creating the air bubbles? What happens to the pressure? Is it sealed and the pressure increases? How are you heating it? Is there any flow present?

If you apply 1000W to a small body of water like this it is going to completely boil the water pretty quickly. Then there is no liquid water and therefore no air bubbles.

[oliveira1820]

The recipient is filled with 85% of liquid water and the rest 15% is air that already is inside the container. The simulation starts with the water and air already inside and it´s a closed container.

The pressure raises from 0 to 30 bar and "when stabilizes" keeps oscilating between 28 and 31 bar.

The energy source is a Bulk Total Source, 1000W distributed in a cylinder with 3 mm height.

Does the water turns all to gas if the pressure is 30 bar? I don´t think so

[ghorrocks]

In that case if the container is just sitting around the water will fall to the bottom and air rise to the top and there will be no bubbles. If there are air bubbles then something will need to generate them. What is the physical process which generates the air bubbles?

[oliveira1820]

I thought that air would mix with water and behave as a dispersed fluid, there´s where the necessity for bubble diameter definiton came.

So is it beter to work with air as a continuous fluid? Or even use the Free Surface Model and the Homogeneous Model?

Also, keeping the thinking, will the water bubbles form, or rise like the air?

[ghorrocks]

I have no idea what you are modelling, what results you are trying to get or what you are trying to achieve. I cannot answer these questions.

Air and water does not mix under normal circumstances. That is why a glass of water has no bubbles in it. If you have bubbles in the water then something put them there. As I have no idea what you are doing I cannot say what caused the bubbles - or even if bubbles are likely to be present.

[oliveira1820]

What I´m modelling is so simple as this: A cylotron liquid with 3,8ml of Volume target. The proton beam hits the target and deploys energy (1000W as heat). Inside there is 85% water and 15% air. Tha target is cooled by water surrounding it. I want to see how the pressure and temperature varies with the incident energy and volume fractions.

I know that in the real case, with 1000 W I have 30 bars.

[ghorrocks]

Isn't this just simple thermodynamics and heat transfer? Why do you need to do CFD of this? Can't a hand calculation work it out?

[oliveira1820]

No, cause after I have te simulation behaving like in reality I want to study the influence of different cooling water temperatures and target design, and also later define the Bether deposition energy formula as heat source.