How to use axisymmetric model?
 

I am modelling a simple case(a jet in a cylinder.) In order to save some time, I choose axisymmetric model in solver. But it doesn't work until I change it to 2d model. Is there anybody can tell me what happen here?( In boundary condition, I set one side as axis. ) Another question: In my opinion, if I set boundary as axis, it should be axisymmetric model.Why should I choose it again in solver? Is there any contradict?

Re: How to use axisymmetric model?
 

hi

you got to choose axisymmetry,to differentiate between symmetric and axisymmetric model. Axisymmetric model will have to sweep 360 degrees.

Re: How to use axisymmetric model?
 

Your axis must be 0x.

Re: How to use axisymmetric model?
 

hi axisymetry will work for 2d only. you can't set axisymmetry for 3d. that to in 2d ,plane should be xy-plane and axis of symmetry should be x-axis.

Re: How to use axisymmetric model?
 

Thanks, I changed my model according to your suggestion, and it works

Re: How to use axisymmetric model?
 

I too am using an axisymmetric mesh and it seems to work fine BUT when activated as axisymmetric, if I then do a "grid check" it says FAILED as "invalid axisymmetric grid-there are 290 nodes below the x-axis" If I switch back to 2D only grid check is fine. I have orientated x-axis as rotational axis and set BC accordingly. What, if anything, have I done wrong?

Chief

Re: How to obtain mean flow
 

hi, I am modeling packed bed column. I would like to know that I can I obtain/extract mean flowrate for the selected region in the packed bed reactor? Thanks Lee

Re: How to use axisymmetric model?
 

hi There shd not be any element below X-axis for axisymmetric problem. Try to change the geometry in gambit and orient in XY plane, do meshing & then import the mesh in Fluent with Axisymmetric.

Mahesh

Re: How to use axisymmetric model?
 

Mahesh,

thanks. I have a correct grid and mesh when 2D option is selected. A grid check passes fine. When the axis of rotation (also the x axis) is defined as an axis BC and the axisymmetric model is selected the grid check then fails. It is as if when the grid is rotated around the central axis it counts the nodes which have been swept around as being below the x axis. Well of course they would be because they have been swept around 360 degrees! Perhaps it is just a software glitch. The simulation seems to run fine anyway but I do not have the confidence to ignore the error message. I know that the bouyancy model I am using is very unstable and I am just trying to cover any possible areas of ambiguity.

cheers

Chief

Re: How to use axisymmetric model?
 

when you have axisymmetric shape you must modeling only one half of the problem then define-->models --> solve --> axisymmetric then other condition and iterate

Re: How to use axisymmetric model?
 

1)For axisymmetrical cases, the mesh must lie in the +y half of the plane. Fluent will use the x-axis as the axis of rotation. Any portions of cells falling below the x-axis will result in negative volumes.

Re: How to use axisymmetric model?
 

ok cheers

Chief

hi,i want to model a rotational disk,which one should i choose?axisymmetric or axisymmetric swirl?(i don't have a swirling flow!)
in addition,we could assign rotational speed to walls in both models,what is the difference between them?
tnx.

Axisymmetric model is used when the geometry is axisymmetric (for example, flow through a pipe, where you can model just a 2D half-section of the pipe). Here, there is no flow in the z-axis.
In axisymmetric swirl, there is swirling flow in the z-axis (normal to the geometry plane).
In your case, you can model it like a stirred tank, by giving a rotational velocity to the walls.

Thank you for your reply
I am trying to model a flow on a rotating disk,so I have a velocity component normal to the plane,you mean that I should use axisymmetric swirl model?
tnx!

Reference values for axisymmetric model
 

Hi
I am modelling flow past a bullet which is an axisymmetric model.
But the Cd value i am getting does not match with the experimental values.
how do i set the reference area for getting the correct value of Cd?

Hello, Jeffery
I also have the same problem with you (mesh cheking problem for axisymmetric model).
I think you should translate the mesh so that all the nodes are above the rotational axis, here the x-axis. Otherwise, there can be some calculation mistakes.
For details please read ANSYS user's guide Chapt. Translating the mesh.

Best regards.

2D axisymmetric
 

Hi,
I would like to ask if it is possible to view the results of a simulation using a 2D axisymmetric model in 3D?

I don not think so. The axisymmetric model is only available in 2d simulations.

Thank you huanxiongkuai
 

Thank you huanxiongkuai

I don not think so. The axisymmetric model is only available in 2d simulations.[/QUOTE]