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Rotation Velocity in MRF for a Rotor

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Old   September 16, 2015, 09:37
Default Rotation Velocity in MRF for a Rotor
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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
File Type: jpg velocity_CW.jpg (61.3 KB, 70 views)
File Type: png velocity_CCW.png (190.0 KB, 54 views)
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Old   September 16, 2015, 17:11
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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.
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Old   September 16, 2015, 21:34
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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
File Type: png blade.png (37.1 KB, 59 views)
File Type: png moving_zone.png (44.4 KB, 53 views)
File Type: png stationary_zone.png (29.7 KB, 50 views)
File Type: png Velocity_Formulation.png (10.3 KB, 44 views)
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Old   September 16, 2015, 22:03
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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.
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Old   September 17, 2015, 00:16
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That is mistake to put translation in Rotor.

Frame motion is enabled in stationary zone (Speed = 0rpm) to make zones periodic (Conformal).
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Old   September 17, 2015, 09:20
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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.
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blade, helicopter rotor, multiple reference frames

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