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-   -   Rotational Velocity (http://www.cfd-online.com/Forums/cfx/22828-rotational-velocity.html)

KBanks July 11, 2006 05:03

Rotational Velocity
 
Hi everyone, I am sure I am missing something obvious, but I am having problems when writing a user macro for automated post processing. I am simulating a compressor stage and in the macro, I need to get the value of the rotational speed of the blade. How do I get this out? It seems like it should be trivial, but both "Velocity Rotational" and "Velocity Circumferential" are gas velocities and give slightly wrong values.

HekLer July 11, 2006 11:19

Re: Rotational Velocity
 
"Rotation Velocity" will give you the magnitude.

"Rotation Velocity X", ""Rotation Velocity Y", "Rotation Velocity Z" will give you the individual components.

Robin July 11, 2006 12:50

Re: Rotational Velocity
 
This is the local velocity, not the angular rotation speed.

HekLeR July 17, 2006 22:21

Re: Rotational Velocity
 
ok, sorry let me be more specific:

Rotation Velocity = omega X R

where omega is the angular velocity you provided during preprocessing and R is the radial distance from your axis.

Or, do you want the fluid velocity at the blade resolved into radial/circumferential/axial components? If so, then if you enable turbo mode for your case (if you have set it up during preprocessing correctly) Post will calculate this. Or you can enter CEL expressions to calculate v_r,v_theta,v_z from v_x,v_y,v_z.


KBanks August 4, 2006 05:09

Re: Rotational Velocity
 
I know how to do it now thanks HekLer - I wasn't looking for fluid components - it is clear how to get those from the documentation. I wanted to know how to get out my blade rotational speed which Robin has answered in another post. Thanks to all.


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