Wind rotor states

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Table of Contents

• 1. Wind rotor states
  • 1.1. Turbulent Wake State
  • 1.2. Vortex Ring State
  • 1.3. References

1 Wind rotor states

different states and its relation with Ct and axial induction factor (a), refer to Fig. 1 a>0.5 should not occur in the major design range of a wind turbine ¹

1.1 Turbulent Wake State

What is turbulent windmill state? When axial induction factor, 0.5<a<1

Features:

• low Cp (close to 0)
• high Ct, (1-2)
• Rotor is similar like a solid disk perpendicular to the flow
• not desirable for wind turbine operation

Disadvantages

• vibration
• buffeting

In the turbulent wake state, large variations in the experimental data indicate tha the flow is rather unstable² Rear Rotor is operating at turbulent wake state Cp is unstable in turbulent wake state

history: Glauert, Wilson, Lissaman

figures/cp_ct_vs_a_wilson1974.pdf

figures/force_vs_rotor_states.pdf

1.2 Vortex Ring State

Shetty, Omkar, and Michael Selig. "Small-scale propellers operating in the vortex ring state." 49th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition. 2011.

1.3 References

 

Footnotes:

¹

DEFINITION NOT FOUND.

²

Sørensen, J. N., W. Z. Shen, and X. Munduate. "Analysis of wake states by a full‐field actuator disc model." Wind Energy: An International Journal for Progress and Applications in Wind Power Conversion Technology 1.2 (1998): 73-88.

no satisfactory theories exist for turbulent windmill state. extensive research has been done on this problem in connection with helicopter rotor theory. Rotor performance ofr the entire range of a is discussed by Wolkovitch ³

³

Wolkovitch, Julian. "Analytical Prediction of Vortex‐Ring Boundaries for Helicopters in Steep Descents." Journal of the American Helicopter Society 17.3 (1972): 13-19. Lock, Christopher Noel Hunter, H. Bateman, and H. C. H. Townend. An extension of the vortex theory of airscrews with applications to airscrews of small pitch, including experimental results. HM Stationery Office, 1926. ¹ Wilson, Robert E., and Peter BS Lissaman. "Applied aerodynamics of wind power machines." NASA STI/Recon Technical Report N 75 (1974).

• 2.5, wind turbine engineering design, eggleston 1987
• Analysis of wake states by a full‐field actuator disc model
• Stoddard, F. S. "Momentum theory and flow states for windmills." Wind Technology Journal, vol. 1, Spring, 1977, p. 3-9. 1 (1978): 3-9.

Author: kaiming

Created: 2019-03-27 Wed 18:43

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