An Experimental Investigation of Vortex Rings and Helicopter Rotor Wakes Using a Laser Doppler Velocimeter

Abstract : The report describes a laser Doppler velocimeter (LDV) capable of performing measurements in vortex cores, presents detailed measurements of structure and stability of vortex rings and also presents measurements in the wake of a model helicopter rotor. The use of conventional instrumentation such as hot wire anemometer for measuring velocity in vortex filament is hampered by probe interference and the difficulty of calibrating the probe in a flow field where the velocity is changing rapidly in magnitude and direction. For these reasons, a laser Doppler velocimeter (LDV) is used throughout these experiments. The LDV measures the velocity of smoke particles by measuring the Doppler shift of laser light scattered from the particles. (Modified author abstract)

[1]  S. Widnall.  The stability of a helical vortex filament , 1972, Journal of Fluid Mechanics.

[2]  A. E. Lennert,et al.  Development of a Laser Velocimeter to be Used in AEDC Wind Tunnels. , 1970 .

[3]  N. S. Barnett,et al.  Private communication , 1969 .

[4]  J. J. Sir Thomson,et al.  A Treatise on the Motion of Vortex Rings: An Essay to Which the Adams Prize Was Adjudged in 1882, in the University of Cambridge , 1883 .

[5]  Robert S. Brodkey,et al.  The phenomena of fluid motions , 1967 .

[6]  E. F. Northrup.  An experimental study of vortex motions in liquids , 1911 .

[7]  C. Tung,et al.  Motion and Decay of a Vortex Ring , 1967 .

[8]  N. A. Chigier,et al.  Tip vortices: Velocity distributions , 1971 .

[9]  Carl-Heinz Krutzsch.  Über eine experimentell beobachtete Erscheinung an Wirbelringen bei ihrer translatorischen Bewegung in wirklichen Flüssigkeiten , 1939 .

[10]  M. J. M. Hill,et al.  On a Spherical Vortex , 1894 .

[11]  T. Kambe,et al.  Motion of Distorted Vortex Rings , 1971 .

[12]  Michael P. Scully.  A METHOD OF COMPUTING HELICOPTER VORTEX WAKE DISTORTION , 1967 .

[13]  M. Sadron.  Contribution à l'étude de la formation et de la propagation des anneaux de tourbillon dans l'air , 1926 .

[14]  E. H. Linfoot.  Principles of Optics , 1961 .

[15]  P. Saffman,et al.  The Velocity of Viscous Vortex Rings , 1970 .

[16]  V. O'brien.  Steady spheroidal vortices—More exact solutions to the Navier-Stokes equation , 1961 .

[17]  H. Pocklington.  III. The complete system of the periods of a hollow vortex ring , 1895, Proceedings of the Royal Society of London.

[18]  Y. Yeh,et al.  Localized fluid flow measurements with an He-Ne laser spectrometer , 1964 .

[19]  Warren H. Stevenson,et al.  Bibliography on Laser Doppler Velocimeters: Theory, Design and Applications, , 1972 .

[20]  L. E. Fraenkel,et al.  Examples of steady vortex rings of small cross-section in an ideal fluid , 1972, Journal of Fluid Mechanics.

[21]  R. H. Magarvey,et al.  The Formation and Structure of Vortex Rings , 1964 .

[22]  J. Sullivan,et al.  On the stability of vortex rings , 1973, Proceedings of the Royal Society of London. A. Mathematical and Physical Sciences.

[23]  W. Thomson.  4. On Vortex Atoms , 1869 .

[24]  T. Maxworthy.  The structure and stability of vortex rings , 1972, Journal of Fluid Mechanics.

[25]  J. Hodkinson,et al.  Particle sizing by means of the forward scattering lobe. , 1966, Applied optics.

[26]  J. Turner,et al.  Buoyant vortex rings , 1957, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences.

[27]  Y. Oshima.  Motion of Vortex Rings in Water , 1972 .

[28]  Gary M. Johnson.  RESEARCHES ON THE PROPAGATION AND DECAY OF VORTEX RINGS. , 1970 .

[29]  Donald B. Bliss,et al.  Theoretical and Experimental Study of the Stability of a Vortex Pair , 1971 .

[30]  J. B. Rorke,et al.  Wind Tunnel Simulation of Full Scale Vortices , 1972 .

[31]  William Mitchinson Hicks,et al.  XV. Researches on the theory of vortex rings.—Part II , 1885, Philosophical Transactions of the Royal Society of London.

[32]  R. J. Goldstein,et al.  Measurement of Laminar Flow Development in a Square Duct Using a Laser-Doppler Flowmeter , 1967 .

[33]  M J Rudd,et al.  A new theoretical model for the laser Dopplermeter , 1969 .

[34]  L. E. Fraenkel,et al.  On steady vortex rings of small cross-section in an ideal fluid , 1970, Proceedings of the Royal Society of London. A. Mathematical and Physical Sciences.

[35]  Anton J. Landgrebe,et al.  An Analytical and Experimental Investigation of Helicopter Rotor Hover Performance and Wake Geometry Characteristics , 1971 .