# CFX Pre. Definition of rotating/non-rotating boundaries for a radial compressor

 User Name Remember Me Password
 Register Blogs Members List Search Today's Posts Mark Forums Read

 LinkBack Thread Tools Search this Thread Display Modes
 October 12, 2015, 05:31 CFX Pre. Definition of rotating/non-rotating boundaries for a radial compressor #1 New Member   Anton Join Date: Oct 2015 Posts: 13 Rep Power: 10 Hi, I am a newbie in ANSYS/CFX/CFD, so sorry for very basic questions I have a compressor wheel (Domain), with Subdomains: Inlet, Outlet, Hub, Schroud etc. I have defined everything through QuickSetup Mode. The wheel (Domain) is rotating at 37000 rpm. The thing I can't clearly understand is why some parts boundaries are rotating, some are static and some are counterrotating. The logic says if the wheel (domain) is rotating, then I define "domain motion" at 37000 rpm, and everything is static in that coord. system, except of the shroud, which is "counter rotating", which makes it static in absolute coord. system. Or, alternatively, if domain coord. system is static, then all parts should be rotating, and the shroud is static in both domain and absolute coord. system. But the shouldn't be all 3 options at the same time - rotating, static, counterrotating. Where am I wrong?

 October 12, 2015, 07:19 #2 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,571 Rep Power: 141 I do not quite understand your question - but the concept is reasonably straight forward. Obviously the rotor spins and the shroud is still. But a better way of thinking about it is to imagine a rigid mesh (ie not deforming and only able to spin) describing the fluid volume around the rotor and shroud. The mesh around the rotor obviously spins with the rotor and the mesh in the shroud is stationary, but you can see that there is some flexibility in where you can define the transition from rotating to stationary. Then on the rotating frame of reference you can either have a stationary wall (which rotates with the reference frame) or a counter rotating wall (which is stationary in the absolute frame). And on the stationary frame you can either have a stationary wall (which is stationary in the absolute frame) or a rotating frame (which rotates.. obviously).

 October 12, 2015, 11:26 #3 New Member   Anton Join Date: Oct 2015 Posts: 13 Rep Power: 10 I mean, when I am doing CFX-Pre it automatically (New Case -> Simulation Type -> Turbomashinery) I get all 3 types - static, rotating and counter rotating. So what is the sense of making counter rotating part on a rotating frame, instead of a simply stationary part?

 October 12, 2015, 20:35 #4 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,571 Rep Power: 141 As I said, think about what the mesh has to do to describe the motion. That tells you what needs to rotate and what needs to be stationary. Then you assign static, rotating and counter rotating based on that.

 Tags coordinate system, domain, rotation

 Thread Tools Search this Thread Search this Thread: Advanced Search Display Modes Linear Mode

 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 OffTrackbacks are Off Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post saisanthoshm88 CFX 11 February 17, 2021 12:30 LynchMobster47 Main CFD Forum 0 April 10, 2012 23:43 RossFS ANSYS Meshing & Geometry 4 November 10, 2011 03:38 rystokes CFX 0 January 12, 2010 07:14 Stewart Long CFX 2 October 28, 2008 05:05

All times are GMT -4. The time now is 19:31.

 Contact Us - CFD Online - Privacy Statement - Top