CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > FLUENT

Ways to simplify a flow hrough cylinder with swirl

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Display Modes
Old   July 15, 2015, 10:26
Default Ways to simplify a flow hrough cylinder with swirl
  #1
New Member
 
Karthik S
Join Date: Jul 2015
Posts: 17
Rep Power: 2
skarthik is on a distinguished road
Dear All,

I am working on a project to develop a model to predict the flow distribution in a micro gas turbine in Fluent.

I have defined the boundary conditions with values for inlet mass flow rate and outlet pressure, and a no-slip condition on the walls. Please refer to the attached image. Capture.JPG

I am able to solve this 3D model as a whole, but I would like to reduce the computation time by simplifying the model. Is it possible to take only a quadrant and solve for it? I have not tried it, but have heard that CFX can do this type of simulation for turbo machines (mixing plane model). I guess this is something like the axisymmetric method but still 3D and also includes my swirl vanes, which would not be possible in 2D axisymmetric.

Please comment if this would work and where should I look for some guidance to do this type of simulation. Also, let me know if there is another way to do this.

Thanks,
Karthik
skarthik is offline   Reply With Quote

Old   July 15, 2015, 11:13
Default
  #2
New Member
 
Sebastian Magee
Join Date: Jul 2015
Posts: 4
Rep Power: 2
SMagee is on a distinguished road
It seems to me that what your looking for is called rotationally periodic conditions or cyclic conditions. From the image it looks like you have 60 (hexagonal) simmetry.
So, reduce the model to a 60 sector, in the mesher sellect the boundary as symetric, then in Fluent use the TUI to apply periodic conditions this is, if I remmenber correctly in: boundary conditions->make periodic.
I find this option to be very useful when modeling cylindric objects.
SMagee is offline   Reply With Quote

Old   July 15, 2015, 12:45
Default
  #3
New Member
 
Karthik S
Join Date: Jul 2015
Posts: 17
Rep Power: 2
skarthik is on a distinguished road
Sebastian,

Thank you.. This looks like what I am looking for. Will try it out and let you know how it goes.

To all,
Googled rotationally periodic glows and found this: 'http://www.cfd-online.com/Forums/fluent/105041-fluent-periodic-boundary-condition-solved-tutorial.html'
Could be really useful!
skarthik is offline   Reply With Quote

Old   July 16, 2015, 03:02
Default
  #4
New Member
 
Sebastian Magee
Join Date: Jul 2015
Posts: 4
Rep Power: 2
SMagee is on a distinguished road
There is also a page or two in ANSY's help that may be helpful
SMagee is offline   Reply With Quote

Old   July 16, 2015, 06:35
Default
  #5
New Member
 
Karthik S
Join Date: Jul 2015
Posts: 17
Rep Power: 2
skarthik is on a distinguished road
Hey,

I get an error when using match control saying that the geometry/topology do not match.

I just realized that the swirl vanes are actually not symmetric. There are 7 vanes. I think this could be the reason for the error, as I tried to cut my model into a section of 90 degrees.
So I am working on a solution for this, and was wondering if you would know of any method to remove the swirl vanes, and still provide a swirl motion. I know that this could be done at the inlet of the model using cylindrical coordinates and defining a tangential velocity/mass flow rate. But I want the inlet to be axial and the swirl should start only at the inner cylinder. Do you know how to apply this to an arbitrary plane located at the place where the swirl vanes would be?
Thanks.
skarthik is offline   Reply With Quote

Old   July 16, 2015, 09:43
Default
  #6
New Member
 
Sebastian Magee
Join Date: Jul 2015
Posts: 4
Rep Power: 2
SMagee is on a distinguished road
You could design a turbine with 6 vanes and use 60 or 120 but not 90. Or the cobustor to have 51.4 symetry, and use the apropiate settings.
Or if you want to keep the current design divide the model in two, the first from the inlet to the begining of the combustor cylinder, after the vanes; the second from there on till the outlet.
The first would have 360/7=51.4 symmetry, the second 60. For this option you would have to export the profile of the velocities at the outlet of the first part and supply these as the inlet velocity profiles to the second. (you will have to append the profile from 0 to 8.4 (60-51.4) to make the full 60 profile that you need for the second part)

I don't know of any simpler way to accomplish the swirl from uniform inlet.
SMagee is offline   Reply With Quote

Old   July 16, 2015, 09:51
Default
  #7
New Member
 
Karthik S
Join Date: Jul 2015
Posts: 17
Rep Power: 2
skarthik is on a distinguished road
Thank you for your input. I will try them out.
skarthik is offline   Reply With Quote

Old   July 21, 2015, 05:25
Default
  #8
New Member
 
Karthik S
Join Date: Jul 2015
Posts: 17
Rep Power: 2
skarthik is on a distinguished road
Hey Sebastian,

I tried to implement your suggestions.. I am able to run the simulation properly when I removed the swirl vanes from the model and modified the holes (14 annular holes) so that I can use a section of 51.4degrees with cyclic region symmetry. The match control works fine without errors.

But when I included the swirler, things dont work well, and I get an error in match control saying that the two periodic faces do not have the same topology or geometry. I am not sure what goes wrong, because the two faces are similar. I have attached the images here.

Is it something wrong with the coordinate system that I have defined?

Thanks!
Karthik S

1.jpg

2.jpg
skarthik is offline   Reply With Quote

Reply

Tags
fluent, mixing plane, simplified body

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Swirl flow recirculation mfmohdyasin OpenFOAM Running, Solving & CFD 4 June 12, 2015 10:20
flow around a circular cylinder with velocity inlet and outflow outlet shuoxue OpenFOAM 1 March 3, 2014 11:42
benchmark: flow over a circular cylinder goodegg Main CFD Forum 12 January 22, 2013 12:47
flow around a cylinder pXYZ Main CFD Forum 14 July 25, 2011 10:05
flow resistance of cylinder in parallel flow Ralf Schmidt Main CFD Forum 3 May 11, 2009 02:26


All times are GMT -4. The time now is 02:42.