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-   -   The difference between frozen rotor and unsteady frozen rotor in turbo machinery? (http://www.cfd-online.com/Forums/cfx/110547-difference-between-frozen-rotor-unsteady-frozen-rotor-turbo-machinery.html)

samane_81 December 13, 2012 18:35

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

Far December 15, 2012 14:13

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.

samane_81 January 5, 2013 10:44

Dear far
Thank you very much! It helps me a lot!

topsedar January 1, 2015 16:16

Dear Far
I was searching to find out the difference between Stage and Frozen Rotor.

you mentioned that:

Quote:

Originally Posted by Far (Post 397701)
Its disadvantage is that, if gives you the solution at the single relative position.

may I ask you kindly make a clarification about your statement?

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


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