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The dynamic induced velocity field of a model rotor in hover conditions

Published online by Cambridge University Press:  04 July 2016

T. J. Ellenrieder
Affiliation:
Department of Aerospace EngineeringUniversity of BristolBristol, UK
P. R. Brinson
Affiliation:
Department of Aerospace EngineeringUniversity of BristolBristol, UK

Abstract

Results obtained from measurements of the dynamic induced velocity field beneath a model rotor are presented. The collective and cyclic pitch of a four bladed rotor of 1·54 m diameter were excited at frequencies up to 1·5 times rotor shaft speed. Flow measurements were taken using hot wire anemometry probes and a laser doppler anemometer. A range of radial and vertical positions near the rotor disc were investigated.

Analysis of the dynamic induced flow response is conducted in the frequency domain and it is found that there are significant radial and azimuthal variations which depend on the frequency of excitation. It is also observed that a change in the character of the inflow response occurs near and above the shaft rotational frequency and that vertical measuring distance from the rotor significantly affects the measured responses.

Some results for the case of cyclic excitation are given. These show, that contrary to momentum theory predictions, the highest induced velocities in the dynamic case do not occur over the area of the disc where the blade pitch is at its maximum.

Overall, the results show that the dynamic induced velocity field is highly complex and heavily influenced by the distribution of time varying shed vorticity within the wake.

Type
Research Article
Copyright
Copyright © Royal Aeronautical Society 1998 

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References

1. Carpenter, P.J. and Fridovich, B. Effect of a rapid blade pitch increase on thrust and induced velocity response of a full-scale helicopter rotor, NACA TN3044, 1953.Google Scholar
2. Mangler, K.W. and Squire, H.B. The induced velocity field of a rotor. Aeronautical Research Council, RM No 2642, 1953.Google Scholar
3. Ormiston, R.A. An actuator disc theory for rotor wake induced velocities, Agard Specialists meeting on the Aerodynamics of Rotary Wings, 1972.Google Scholar
4. Ormiston, R.A. Application of simplified inflow models to rotor craft dynamic analysis, J Amer Heli Soc, 1976, 21, (3).Google Scholar
5. Pitt, D.M. and Peters, D.A. Theoretical prediction of dynamic inflow derivatives, Vertica, 1981, 5, (2).Google Scholar
6. Pitt, D.M. and Peters, D.A. Rotor dynamic inflow derivatives and time constants from various inflow models, 9th European Rotorcraft Forum, 1983.Google Scholar
7. Peters, D.A. and Gaonkar, G.H. Review of dynamic inflow modelling for rotorcraft flight dynamics, Vertica, 1988, 12, (3).Google Scholar
8. Ellenrieder, T.J. Investigation of the Dynamic Wake of a Model Rotor, PhD thesis, Department of Aerospace Engineering, University of Bristol, 1996.Google Scholar
9. Gaonkar, G.H. and Peters, D.A. A Review of dynamic inflow and its effect on experimental correlation, American Helicopter Society Second Decennial Specialists meeting on Rotorcraft Dynamics, California, 1984.Google Scholar
10. Chen, R.T. and Hindson, W.S. Influence of dynamic inflow on the helicopter vertical response, Vertica, 1987, 11, (1).Google Scholar
11. Ellenrieder, T.J. and Brinson, P.R. Experimental investigation of helicopter coning/inflow dynamics in hover. Twentieth European Rotorcraft Forum, Amsterdam, 1994.Google Scholar
12. Houston, S.S. Identification of factors influencing rotorcraft heave axis damping and control sensitivity in the hover, Royal Aircraft Establishment, AE Technical Report 88067, 1989.Google Scholar
13. Peters, D.A. and Haquang, N. Dynamic inflow for practical applications, J Amer Heli Soc, 1988, 33, (4).Google Scholar
14. Su, A., Yoo, K.M. and Peters, D.A. Extension and validation of an unsteady wake model for rotors, J Aircr, 1992, 29, (3).Google Scholar
15. Prouty, R.W. Even more helicopter aerodynamics, Rotor & Wing International, Phillips Publishing, 1992.Google Scholar
16. Houston, S.S. and Black, C.G. On the identifiability of helicopter models incorporating higher order dynamics, Royal Aircraft Establishment Tech Memo Fm 37, 1990.Google Scholar
17. Bradley, R., Black, C.G. and Murray-Smith, D.J. Glauert augmentation of rotor inflow dynamics, 15th European Rotorcraft Forum, Amsterdam, 1989.Google Scholar
18. Leith, D.J., Bradly, R. and Murray-Smith, D.J. The identification of coupled flapping/Inflow models for hovering flight, 17th European Rotorcraft Forum, Berlin, 1991.Google Scholar
19. Brinson, P.R. Experimental investigation of coupled helicopter rotor/Body control, 17th European Rotorcraft Forum, Berlin, 1991.Google Scholar
20. Houston, S.S. and Tartellin, P.C. Theoretical and experimental correlation of helicopter aeromechanics in hover, Royal Aircraft Establishment Tech Memo Fm 20, 1989.Google Scholar
21. Lal, M.K. Measurement around a rotor blade excited in pitch, Part 2: Unsteady surface pressure, J Amer Heli Soc, 1994, 39, (2).Google Scholar
22. Liou, S.G., Komerath, M., et al Measurements around a rotor blade excited in pitch, Part 1: Dynamic inflow, J Amer Heli Soc, 1994, 39, (2).Google Scholar