# Rotation Velocity in MRF for a Rotor

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September 16, 2015, 09:37
Rotation Velocity in MRF for a Rotor
#1
Senior Member

Ali
Join Date: Jan 2012
Location: Pakistan
Posts: 134
Rep Power: 16
Hi,

I am simulating a helicopter rotor in Hovering, it's two bladed heli. I setup only one blade with periodic boundary condition and used MRF in Ansys Fluent.

The confusion is about the Rotating Speed input to the Moving Cell Zone. In my case, rotor should rotate Clock-Wise Direction looking from top.

I simulated two situations where once I input a "Positive Rotation Speed i.e. CCW" and in second case I put "Negative Rotation Speed".

Which one is correct? as my case is new, no data is available to compare the results. I attached Velocity vectors in Moving Zone and in Stationary Frame.

The solution is not fully converged in one case so just check the orientation.

One more thing, How can I give Pitch Angle to blade?

Kindly comment and suggest?
Attached Images
 velocity_CW.jpg (61.3 KB, 70 views) velocity_CCW.png (190.0 KB, 54 views)
__________________
Best Regards
Ali

 September 16, 2015, 17:11 #2 Senior Member   JSM Join Date: Mar 2009 Location: India Posts: 192 Rep Power: 20 From your contour image, I assume that Y axis is rotational axis and you need to rotate the blades in CW. Then you need to define (0,0,0) as origin & (0,-1,0) for axis direction and corresponding rotational speed. Negative rotational speed is not recommended. But Fluent can solve it. I can not understand the question about pitch angle. Why you need to input in Fluent? If your mesh is periodic, then Fluent will take the pitch angle automatically. __________________ With regards, JSM

September 16, 2015, 21:34
#3
Senior Member

Ali
Join Date: Jan 2012
Location: Pakistan
Posts: 134
Rep Power: 16
From my contours, which case presents real flow physics (i.e. in reality, blades will move Clockwise)?

I am still confused. I am posting some more pictures of my simulation setup.
Attached Images
 blade.png (37.1 KB, 59 views) moving_zone.png (44.4 KB, 53 views) stationary_zone.png (29.7 KB, 50 views) Velocity_Formulation.png (10.3 KB, 44 views)
__________________
Best Regards
Ali

 September 16, 2015, 22:03 #4 Senior Member   JSM Join Date: Mar 2009 Location: India Posts: 192 Rep Power: 20 Your case set up is not correct. For rotor zone, you set Translation motion. It should be rotational motion. Also why are you enabling "Frame motion" for stationary zone. Please refer some Fluent tutorials in turbo machinery to understand better. __________________ With regards, JSM

 September 17, 2015, 00:16 #5 Senior Member   Ali Join Date: Jan 2012 Location: Pakistan Posts: 134 Rep Power: 16 That is mistake to put translation in Rotor. Frame motion is enabled in stationary zone (Speed = 0rpm) to make zones periodic (Conformal). __________________ Best Regards Ali

 September 17, 2015, 09:20 #6 Senior Member   JSM Join Date: Mar 2009 Location: India Posts: 192 Rep Power: 20 No need to enable frame motion to make periodic. You can define axis origin and direction without enabling that. That's the reason, I am recommending to refer some fluent tutorials in turbo machinery. __________________ With regards, JSM

 Tags blade, helicopter rotor, multiple reference frames