## Fluids

#### How to create the air flow around the moving wall of a cylinder?

• Raj007
Subscriber

Hello all,

I am working on moving pipe-like geometry. As I need a constant velocity at inlet and outlet or constant velocity profile. I needed to use the velocity of the walls the same as an inlet around 45 cm/s. There is heat propagating inside the pipe.

But now, the problem is, I want to study the cooling of the pipe to atmospheric temperature conditions after heating. So I have specified one more cylinder around the geometry with the velocity at the inlet of the air domain as 0.1 cm/s.

After the simulation has run. I can see a backflow in the air domain at the outlet. I do not know, this is because of the velocity difference or what? Could anyone explain me?

Also if there are any geometry errors please let me know.

(I am attaching velocity contour of the symmetry of the geometry)

Thank you

Raj

• Rob
Ansys Employee
If you want a constant velocity profile why not use a profile on the inner pipe inlet? Setting a moving wall may well be causing some oddities in the flow in the outer section. As I can't see what boundary conditions have been set it's hard to comment.
• Raj007
Subscriber
Actually, it is a moving fiber. So, just to make the model seem a real prototype. I wanted to give the moving wall condition, to avoid shear at the wall.
• Rob
Ansys Employee
So it's a solid zone and not a fluid? Sketch out what you have, and what is going on.
• Raj007
Subscriber
It is fluid. I need to model it and find how it reacts with the heat at a certain temperature and I would like to also see how it reacts with atmospheric conditions.
• Rob
Ansys Employee
The fibre is fluid or solid?
• Raj007
Subscriber
Fiber is fluid
• Rob
Ansys Employee
Sketch out the exact problem as I'm not sure what you're actually modelling. If the fibre is fluid why is there a wall around it? If it's actually a pipe in pipe system why would the fluid in the fibre not have a boundary layer profile if it's flowing?