# Air-water in rotating cylinder

• 48 Views
• Last Post 21 May 2019
ham_nola posted this 10 May 2019

Hi

I have an air-water inside a cylinder as shown in the figure below. Red area is the air and blue is the water. The wall (grey in color) is rotating; wall. I want to figure out the transient behavior of air-water mixture inside this domain. Some of the key observations I have are:

1. Wall is not symmetric so I cannot give the wall a rotating velocity (rad/s). Isn't that true!

2. The problem can be solved by giving the mesh motion. But the question is will it capture the transient of the whole process?

3. Is there a better modeling approach for the whole problem!

Thank you.

Regards

ham_nola posted this 11 May 2019

My question is that the rib on the wall will move the liquid in front of it as the mesh moves. But due to mesh motion, the whole domain will rotate at an rpm. Which will not capture true transient of the flow wherein the wall motion will diffuse into the fluid and cause the motion!

Thus, mesh motion will be more suitable for a steady state analysis. However, modeling the transient phenomena to capture the physics of initial motion, how to do that?

The solution I could think of is to define a circular zone, one that encompasses the rib, and another zone is the rest of the domain. Is it a logical approach?

Thank you.

peteroznewman posted this 11 May 2019

I'm not a Fluent expert, but I would simply rotate the gravity vector with time, that way there is no moving mesh, just the cell VOF fractions change with time.

• Liked by
ham_nola posted this 21 May 2019

I've come up with two solutions:

1. The region close to the rib is modeled as one zone....with an interface with another zone.

2. Use dynamic mesh.

Any suggestions?

Thank you.

Regards

HAM