The Vortex Ring State
An airscrew is said to be in the vortex ring state of operation when it
strongly interacts with its own slipstream. This typically occurs on propellers in
fast backward motion, helicopter rotors in descent and manoevre near the ground, wind
turbines with low wind speed regimes, as shown in Fig. 1 above.
In all these cases the fluid passing through the airscrew returns upstream around the
tips, thus creating a strongly turbulent flow field, that is also very noisy. The
vortex ring state is a particular case of blade-vortex interaction (BVI). The
analysis is therefore fairly complicated.
Selected References
- Glauert H. Airplane Propellers, Volume 4, Div. L, in Aerodynamic
Theory, edited by Durand W.F., Dover ed. 1943.
- Andersen P,Breslin JP. Hydrodynamics of Ship Propellers,
Cambridge Univ. Press, 1995.
- Stepniewski WZ, Keys CN. Rotary-Wing Aerodynamics,
Dover Publ, Inc., New York, 1984.
- Gostelow JP. Cascade Aerodynamics, Pergamon Press, 1984.
Full List of References
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