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isosurface in CFD-Post for transient rotor-stator simulations

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Old   May 29, 2012, 13:39
Default isosurface in CFD-Post for transient rotor-stator simulations
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Anyone tried to make an animation of isosurface in CFD-Post for a CFX run with transient rotor-stator?

In my simulation, most part of my isosurface is supposed to be stationary, with only a portion of it being rotated and evolved with time. However, by visually looking at the animation of the isosurface evolution with time, it looks like the whole isosurface is moving together with the rotating domain!

I understand this to be a "visual illusion" due the way that CFD-Post renders the isosurface. In CFX, the "transient rotor stator" approach acutally moves the whole rotating domain, even though you can specify some "counter-rotating" velocity to some faces of the rotating domain. The result, therefore, is a whole domain of elements being rotated with each time step.

Now when we plot an isosurface, or a "volume", CFD renders it based on the underlying elements. If that portion of isosurface is actually stationary, the next timestep since the whole domain is rotated, you will get the impression that the isosurface is following the rotation to the next position. However, in reality, the portion of this isosurface should not be moving!

I'm wondering anyone has some idea how to correct this "illusion". Is there a way in CFD-Post that makes the rendering of "isosurface" or "volume" less depending on the underlying elements so that the time evolution of isosurface or volumes will not see effect from the rotating domain?

Thanks a lot!
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Old   May 29, 2012, 19:07
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In a TRS simulation, if a blob is in a rotating frame of reference but it is actually stationary in the absolute frame then the post processing will show it stationary. So if you see it rotating it is not an illusion, the simulation is predicting that it rotates.
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