- Volume 10 Issue 2
In order to investigate change of vortex structures and its evolving proceses, two dimensional LDV system was used for measurement of velocity vectors of tip vortex, and PIV system was also used for visualizations of tip vortex array for two bladed rotor, respectively. Experiments provided vortex locations, tangential and axial velocity components of tip vortex at six wake ages of 9.5, 10.5, 60.5, 99.5, 129.5, 169.5 and corresponded six wake ages shifted with 180 degrees per each. It was resulted that tip vortices generated by the first blade satisfy Landgrebe's model for their vortex locations even after they were accelerated by the second blade in downstream. Tangential velocity components of tip vortices follow Vatistas' n=2 model on both inside and outside regions of rotor slipstream without loss of vortex circulation. Axial velocity profiles revealed that there were small but significant perturbations just outside the primary vortex core which implies the second blade affects the wake substantially. It was also found that tip paths of each blade were not willing to be coincided intrinsically.
helicopter;tip vortex;two bladed rotor;LDV system;visualization
- Y. O. Han and J. G. Leishman, “Experimental Investigation of Helicopter Rotor Tip Vortex Alleviation Using a Slotted Tip Blade”, AIAA Journal, Vol.42, No.3, pp. 523-535, March 2004. https://doi.org/10.2514/1.3254
- F. H. Schmitz, Rotor Noise, Aeroacoustics of Flight Vehicles: Theory and Practice, Vol.1, NASA Reference Publication 1258, Aug. 1991, Chap.2.
- S. Dawson, A. Hassan, F. Straub and H. Tadghighi, “Blade - Mounted Flap Control of BVI Noise Reduction Proof of Concept Test”, NASA Rept. 195078, July 1995.
- G. L. Crouse, J. G. Leishman and N. Bi, “Theoretical and Experimental Study of Unsteady Rotor/Body Aerodynamic interactions”, Journal of the American Helicopter Society, Vol. 38, No. 1, 1992, pp. 55-64. https://doi.org/10.4050/JAHS.37.55
- M. S. Torok and D. T. Ream, “Investigation of Empennage Airloads Induced by helicopter Main Rotor Wake”, American Helicopter Society 49th Annual Forum, st. Louis, Mo, May 1993.
- Y. O. Han and W. J. Chung, “Mean and turbulent characteristics if tip vortices generated by a slotted model blade”, 5th international Symposium on Engineering Turbulence Modelling and Measurements, September 16-18, Mallorca, Spain, 2002.
- Y. O. Han, J. G. Leishman and A. J. Coyne, “Measurements of the Velocity and Turbulence Structure of a Rotor Tip Vortex,” AIAA Journal Vol35, No3, pp. 477-485, 1997. https://doi.org/10.2514/2.120
- Y. O. Han “Diffused Tip Vortex Structure Generated by a Slotted Tip Rotor Blade,” The 43rd AIAA Aerospace Science Meeting and Exhibition, AIAA Paper 2005-0057, Reno, NV. January 10-13, 2005.
- A. J. Landgrebe, “The Wake Geometry of a Hovering Helicopter Rotor and its Influence on Rotor Performance”, Journal of the American Helicopter Society, 17:4 pp. 2-15. https://doi.org/10.4050/JAHS.17.2
- M. J. Bhagwat and J. G. Leishman, “Correlation of Helicopter Totor Tip Vortex Measurement”, AIAA Journal, Vol.38, No.2, 2000, pp. 301-308. https://doi.org/10.2514/2.957
- A. Bagai, and J. G. Leishman, “A Study of Rotor Wake Development and Wake/Body interaction in Hover”, Journal of the American Helicopter Society, Vol. 37, No. 4, 1992, pp. 48-57. https://doi.org/10.4050/JAHS.37.48
- G. H. Vatistas, V. Kozel and W. C. Mih, “Simpler Model for Concentrated Vortices”, Experiments in Fluids, Vol.24, No. 11, pp. 73-76. https://doi.org/10.1007/BF00198434
- V. R. Corsiglia, R.G. Schwind, And N. A. Chiglier, “Rapid Scanning Three- Dimensional Hot Wire Anemometer Surveys of Wing-Tip Vorices”, Journal of Aircraft, Vol. 22, No. 2, 1985, pp. 158-160. https://doi.org/10.2514/3.45101
- H. Lamb, Hydrodynamics, 6th end., Cambridge Univ. Press, New York, 1932, pp. 592, 593, 668, 669
- A. Ogawa, Vortex Flow, Series on Fine Particle Science and Technology, CRC Press, Boca Raton, FL, 1993, pp. 193-196.
- C. Tung, S. L. Pucci, F. X. Caradonna, and H. A. Morse, “The Structure of Trailing Vortices Generated by Model Rotor Blades”, Vertica, Vol. 7, No.1, 1983, pp. 33-43.