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

Problem with the 2D rotating blade-CFX-12.1

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

Reply
 
LinkBack Thread Tools Display Modes
Old   September 3, 2011, 03:54
Unhappy Problem with the 2D rotating blade-CFX-12.1
  #1
New Member
 
Araz
Join Date: Feb 2011
Location: Canada
Posts: 22
Rep Power: 6
Araz is on a distinguished road
Hi,

I'm trying to do a steady state analysis of the 2D (one element extruded) Rotor blade of a specific compressor. It is located in the mid-span, hub and shroud are symmetry planes.
In the Turbo mode of the CFX-pre, we can only define the angular velocity of the blade and there is no place to introduce the radius. the only way that I found was to define the radius when creating the mesh.
I think that for a 2D simulation we need linear velocity of the blade not the rotational speed. please correct me if I'm wrong.
I tried different ways to setup the simulation but it is not working.
I defined the rpm for rotor, and used the rotating domain option, while using the Stationary Frame for the INLET and OUTLET boundaries. it didn't work.
I used rotating INLET and OUTLET but the solver didn't even start.
I calculated the relative total pressure, total temp. and relative velocity angles of the inlet flow and used them as the INLET boundary conditions and set the domain and the blade as Stationary. it didn't work again.
In the blade (wall) boundary details, I tried to introduce the angular (and the next time linear) velocity of the blade but each time the solver exited with error message.
I also tried using the general mode instead of Turbo mode, but didn't make much difference.
I first used the Translational periodicity and then Rotational periodicity but again bad result.
In all cases I'm starting with a low outlet static pressure and increase it slightly to the actual value in order to prevent the outlet boundary to act as a wall, but this problem happens for the working cases and when i reach the actual static pressure, 100% of the both inlet and outlet act as a wall which prevent the fluid from flowing inside or outside of the domain.
May you please help me to solve the problem? how can I setup the simulation?

Thanks in advance,
Regards,
Araz
Araz is offline   Reply With Quote

Old   September 3, 2011, 05:54
Default
  #2
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,805
Rep Power: 85
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
2D simulations can be either tranlational or rotational. In your case it sounds like a rotational one might be more suitable. Have you done the axial rotor/stator example which comes with CFX? That will show you the basics of how to set this up. And read the best practises guide while you are at it.

If you want more specific help please post an image of your geometry.
ghorrocks is offline   Reply With Quote

Old   September 3, 2011, 06:10
Default
  #3
New Member
 
Araz
Join Date: Feb 2011
Location: Canada
Posts: 22
Rep Power: 6
Araz is on a distinguished road
Dear Glenn,

Thanks for your reply, I have done that tutorial before and gone through the best practices guide. After doing all these I posted my question.

Here is my blade from a front view.

Thanks again
Attached Images
File Type: jpg rotortranslated.jpg (56.6 KB, 49 views)
Araz is offline   Reply With Quote

Old   September 3, 2011, 06:23
Default
  #4
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,805
Rep Power: 85
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
Have a look at the geometry modelled in the tutorial again. Hopefully you can see the difference between it and what you have modelled. You have modelled a very strange rotating machine. I think you will find you cannot model this 2D, but need to model a single blade passage in 3D.
ghorrocks is offline   Reply With Quote

Old   September 3, 2011, 06:50
Default
  #5
New Member
 
Araz
Join Date: Feb 2011
Location: Canada
Posts: 22
Rep Power: 6
Araz is on a distinguished road
Thanks a lot Glenn,

As I said, it is a thin slice of the blade in the mid-span. It is working properly in Fluent, So I hope I can find a way to do so in CFX.
what I don't understand is that, using the velocity triangles, I calculated all the relative flow variables, so by using them as the boundary conditions, we can set the blade and the domain as Stationary and the setup would be exactly like a Stator. I have no problem with stator but I don't know why this is not working properly.
Anyway, Thanks a lot for your time and help
Araz is offline   Reply With Quote

Old   September 3, 2011, 07:54
Default
  #6
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,805
Rep Power: 85
ghorrocks has a spectacular aura aboutghorrocks has a spectacular aura aboutghorrocks has a spectacular aura about
I see, OK then the 2D approach makes sense, providing rotation effects (coriolis, centripetal) are not significant.

Then there should be no need for rotating frames of reference at all. Just get the AOA right and it should all work from there. Do not use turbo mode to set this up as it is a simple stationary model.
ghorrocks is offline   Reply With Quote

Reply

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
Ansys 13 CFX problem on LInux Opensuse 11.4 serendipity CFX 10 August 7, 2012 03:24
[TGrid] overlapping problem for stator and rotor blade kennethaktuba ANSYS Meshing & Geometry 0 January 1, 2010 02:31
cfx mesh problem... mactech001 ANSYS Meshing & Geometry 0 November 5, 2009 03:19
stress analysis of a rotating beam(wind blade) Cheyannne ANSYS 0 October 19, 2009 17:06
Fan Modelling Problem in CFX Jenny CFX 8 September 11, 2007 13:59


All times are GMT -4. The time now is 00:35.