The difference between frozen rotor and unsteady frozen rotor in turbo machinery?

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 December 13, 2012, 18:35 The difference between frozen rotor and unsteady frozen rotor in turbo machinery? #1 New Member   samane Join Date: Dec 2012 Posts: 7 Rep Power: 6 Sponsored Links I want to know the difference between frozen rotor and unsteady frozen rotor in turbo machinery? just for modeling steady and unsteady or something more? for modeling an axial or radial compressor with fixed speed of rotation(for example 750rad/s) which one is better for interface?and why?

 December 15, 2012, 14:13 #2 Super Moderator   Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,329 Blog Entries: 6 Rep Power: 45 Frozen rotor is the steady state method which uses the rotating reference frame to save your computational resources by converting inherently transient turbo-machinery flow into steady state. The difference between frozen rotor and mixing plane (stage method as named in CFX) is that mixing plane mixes the flow and apply the average qualities on the interface for upstream and downstream components. While frozen rotor will pass the true flow to down steam and vice versa. So if you are interested in the wake effect on the downstream component performance then you should use frozen rotor method. Its disadvantage is that, if gives you the solution at the single relative position. So if you want to get the wake effect on the downstream component for all relative positions (as happens in reality) then you should go for the true transient method. There are true transient methods available in the CFX like sliding mesh. They have also introduced some other unsteady methods which relaxes the conditions for the sliding mesh such as equal pitch size on both sides of interface. Unsteady + frozen rotor (do not call it unsteady frozen rotor) method may used to simulate the vortex shedding in the turbine rotor blade trailing edge. That vortex shedding is accomplished through unsteady solver while frozen rotor is used to couple the Nozzle guide van and rotor domains. So you may be interested in finding the relative position which triggers the vortex shedding or suppresses it. crevoise, seyed, kaktus10 and 1 others like this.

 January 5, 2013, 10:44 #3 New Member   samane Join Date: Dec 2012 Posts: 7 Rep Power: 6 Dear far Thank you very much! It helps me a lot!

January 1, 2015, 16:16
#4
New Member

Hossein
Join Date: Apr 2013
Posts: 20
Rep Power: 6
Dear Far
I was searching to find out the difference between Stage and Frozen Rotor.

you mentioned that:

Quote:
 Originally Posted by Far Its disadvantage is that, if gives you the solution at the single relative position.

1- what is the meaning of single relative position? ( where do you mean? )

2- when I am not allowed or not using Frozen Rotor model? ( The same question related to Stage model)

Best Regards,
Abedini

March 18, 2016, 06:14
#5
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Join Date: Apr 2012
Location: Mainz, Germany
Posts: 57
Rep Power: 7
Can you please explain what do you mean by 'Single Relative Position'?

Regards,
Juzer

Quote:
 Originally Posted by Far Frozen rotor is the steady state method which uses the rotating reference frame to save your computational resources by converting inherently transient turbo-machinery flow into steady state. The difference between frozen rotor and mixing plane (stage method as named in CFX) is that mixing plane mixes the flow and apply the average qualities on the interface for upstream and downstream components. While frozen rotor will pass the true flow to down steam and vice versa. So if you are interested in the wake effect on the downstream component performance then you should use frozen rotor method. Its disadvantage is that, if gives you the solution at the single relative position. So if you want to get the wake effect on the downstream component for all relative positions (as happens in reality) then you should go for the true transient method. There are true transient methods available in the CFX like sliding mesh. They have also introduced some other unsteady methods which relaxes the conditions for the sliding mesh such as equal pitch size on both sides of interface. Unsteady + frozen rotor (do not call it unsteady frozen rotor) method may used to simulate the vortex shedding in the turbine rotor blade trailing edge. That vortex shedding is accomplished through unsteady solver while frozen rotor is used to couple the Nozzle guide van and rotor domains. So you may be interested in finding the relative position which triggers the vortex shedding or suppresses it.

 March 18, 2016, 06:52 #6 Senior Member   Maxim Join Date: Aug 2015 Location: Germany Posts: 374 Rep Power: 4 it means that the rotor is frozen in one position and is not moving. Your result is basically the flow in that exact moment. You usually cannot display any periodic 'events' (e.g. pressure pulses from the moving rotor on other objects in the flow). You would need a fully transient simulation for that.

March 18, 2016, 09:32
#7
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Location: Mainz, Germany
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Quote:
 Originally Posted by -Maxim- it means that the rotor is frozen in one position and is not moving. Your result is basically the flow in that exact moment. You usually cannot display any periodic 'events' (e.g. pressure pulses from the moving rotor on other objects in the flow). You would need a fully transient simulation for that.

That would mean that the relative position is fixed between the rotor and the non-rotating domain for all my timesteps of my steady state simulation.

Am I making any wrong interpretations?

Thanks and Regards,
Juzer

 March 18, 2016, 09:41 #8 Senior Member   Join Date: Jun 2009 Posts: 669 Rep Power: 15 You got it, i.e. frozen rotor does not move respect to the stator during the simulation.

 April 5, 2016, 23:12 #9 Member   ali Join Date: Feb 2011 Posts: 37 Rep Power: 8 Now what is the equivalence of sliding mesh in CFX interface model? is that transient rotor stator or stage? thanks

 April 6, 2016, 05:04 #10 Super Moderator   Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,329 Blog Entries: 6 Rep Power: 45 transient rotor stater = sliding mesh. Stage = mixing plane, frozen rotor = multiple rotating reference frame.

 April 7, 2016, 01:59 #11 Member   ali Join Date: Feb 2011 Posts: 37 Rep Power: 8 thanks Sijal, Do you know any example or tutorial for CFX transient rotor stater model?

 April 7, 2016, 13:54 #12 Super Moderator   Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,329 Blog Entries: 6 Rep Power: 45 yes. One is provided with CFX help

 Tags axial compressor, cfx, frozen rotor, interface, unsteady

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