[coolengineer]

Hi,
I am solving the flow though a channel opened on a piston head which is moving inside a cylinder. Here, I am using layering type dynamic mesh. I can see the mesh moving without any problem in Fluent; however, when I were to iterate the solution it gives error as "Error: divergence detected in AMG solver: pressure correction
Error Object: ()"
When I work with ideal gas there is no problem. But when I am to work with a fluid, such a problem occurs. Can anyone advice me anything with that?
Thank you all. I am waiting from you.

[coolengineer]

I think it is because of Continuity. When I use ideal gas as a fluid, Fluent goes on calculations without an error. However, when I chose a fluid, a kind of incompressible fluid, the continuity residual diverges. Would it be because of this?If so, how can I overcome this problem?

[s_fardisi]

Hi

I want to solve a similar problem and had troubles. Did you solve your issue, how?

I want to solve the fluid flow in a non circular culinder-piston configuration.
Originally, I would like to solve it 3D but let's discuss the 2D problem first. The cylinder walls have some curvature, for example each wall can be viewed as a 1/4 of a circle. The piston moves inside this curvilinear cylinder. My question is what is the best way to do it and how should I introduce the moving wall for the piston? Is there a good online help or a tutorial?

P.s.1 I think I have to use a mesh layering but I am not sure how I should account for the motion of the piston. I know Fluent has a pre-set situation for conventional cylinder piston problem in mesh layering but how can I expand it to non circular culinder-piston.

P.s.2 Do I have to use a moving wall? If yes do I have to write a UDF for it and in that case can I still use the mesh layering or I do I need re-meshing then?

Thanks in Advance

Sina

[wlt_1985]

Originally Posted by coolengineer

Hi,
I am solving the flow though a channel opened on a piston head which is moving inside a cylinder. Here, I am using layering type dynamic mesh. I can see the mesh moving without any problem in Fluent; however, when I were to iterate the solution it gives error as "Error: divergence detected in AMG solver: pressure correction
Error Object: ()"
When I work with ideal gas there is no problem. But when I am to work with a fluid, such a problem occurs. Can anyone advice me anything with that?
Thank you all. I am waiting from you.

I would like to have my model by having 'layering' scheme of dynamic mesh. Unfortunately, I am totally new in dynamic mesh and I might need your help in guiding me to have good dynamic mesh modeling which might similar with your case. My model is shown as the attachment. May I have your advise on how to do that. Pls help me. Thanks a lot.

[wlt_1985]

Originally Posted by coolengineer

Hi,
I am solving the flow though a channel opened on a piston head which is moving inside a cylinder. Here, I am using layering type dynamic mesh. I can see the mesh moving without any problem in Fluent; however, when I were to iterate the solution it gives error as "Error: divergence detected in AMG solver: pressure correction
Error Object: ()"
When I work with ideal gas there is no problem. But when I am to work with a fluid, such a problem occurs. Can anyone advice me anything with that?
Thank you all. I am waiting from you.

I would like to have my model as the attachment. I found that 'layering' scheme might be useful for my case which might have similarity with your case. Can please lead me to have proper way in setting the 'layering' scheme of dynamic mesh? Thanks for your help. It is urgent to me. Please help.

[DanielJ]

Originally Posted by coolengineer

I think it is because of Continuity. When I use ideal gas as a fluid, Fluent goes on calculations without an error. However, when I chose a fluid, a kind of incompressible fluid, the continuity residual diverges. Would it be because of this?If so, how can I overcome this problem?

I know it's an old post but I have a question. What motion function do you use??
Do you use In-cylinder piston motion function??

[Master312]

I have 2D model Cylinder and piston. I've 3 interface. basically i set transient mode, ideal gas (for material), Spalart-Almaras turbulent mode.
Dynamic mesh is ON.
Test of "Preview mesh motion" is done.
Piston move and layering meshes done.

But, when i Run solver after 30 time step before the first sliding interface give an error:
"error at node 2: coalesce_rib_faces : can't interpolate data, zones of different type detected"
I need help.
of course i set "events" for interfaces as "create sliding interface", on time.
all sets of mesh checked in pictures.
Thanks.

[Master312]

Originally Posted by Master312

I have 2D model Cylinder and piston. I've 3 interface. basically i set transient mode, ideal gas (for material), Spalart-Almaras turbulent mode.
Dynamic mesh is ON.
Test of "Preview mesh motion" is done.
Piston move and layering meshes done.

But, when i Run solver after 30 time step before the first sliding interface give an error:
"error at node 2: coalesce_rib_faces : can't interpolate data, zones of different type detected"
I need help.
of course i set "events" for interfaces as "create sliding interface", on time.
all sets of mesh checked in pictures.
Thanks.

hello me
you must change your boundary condition of "walls to interface" in "direction" of your interface. in other words you must change all boundary conditions that slide through "motion wall" to interface and then define them in manual interface. in the last you have all boundary conditions of slider with "interface" mode, "no" part of that.