Experimental observations of two dimensional blade-vortex interaction

Blade-vortex interaction is the source mechanism for a prominent impulsive noise created by rotorcraft. An experimental study of two-dimension al blade-vortex interaction was performed to determine controlling parameters governing the strength of the blade-vortex interaction process. The interaction process is shown to involve a combination of effects on the vortex, including changes in trajectory and distortion of the vortex core shape while the blade undergoes significant transient loading. Calculations of the acoustic field produced by the interaction using measured unsteady blade surface pressure data are presented. The effects of the interaction process on the blade and the vortex are shown to be increased by both reduction of blade-to-vort ex spacing and increase in blade loading.

[1]  Sheila E. Widnall,et al.  Helicopter Noise due to Blade‐Vortex Interaction , 1971 .

[2]  Interactions of Airfoils with Gusts and Concentrated Vortices in Unsteady Transonic Flow , 1983 .

[3]  T. Theodorsen.  General Theory of Aerodynamic Instability and the Mechanism of Flutter , 1934 .

[4]  N. Sankar,et al.  Unsteady aerodynamics of an airfoil encountering a passing vortex , 1985 .

[5]  Jay C. Hardin,et al.  Concepts for reduction of blade/vortex interaction noise , 1987 .

[6]  G. P. Succi,et al.  The prediction of helicopter rotor discrete frequency noise , 1982 .

[7]  M. Luttges,et al.  Control of Wake Structure Behind and Oscillating Airfoil , 1986 .

[8]  Donald R. Wilson,et al.  Experimental Investigation of the Parallel Vortex-Airfoil Interaction at Transonic Speeds , 1989 .

[9]  D. A. Boxwell,et al.  Model- to Full-Scale Comparisons of Helicopter Blade-Vortex Interaction Noise , 1984 .

[10]  H. H. Hubbard,et al.  Aeroacoustic research facilities at NASA Langley Research Center: Description and operational characteristics , 1983 .

[11]  D. Poling,et al.  The Response of Airfoils to Periodic Disturbances —The Unsteady Kutta Condition , 1984 .

[12]  J. C. Hardin,et al.  Aeroacoustic interaction of a distributed vortex with a lifting Joukowski airfoil , 1984 .

[13]  W. Sears,et al.  Some Aspects of Non-Stationary Airfoil Theory and Its Practical Application , 1941 .

[14]  Joseph Katz,et al.  Behavior of Vortex Wakes from Oscillating Airfoils , 1978 .

[15]  W. R. Splettstoesser,et al.  Prediction of Helicopter Rotor Impulsive Noise Using Measured Blade Pressures , 1987 .

[16]  E. R. Booth,et al.  Two-dimensional blade-vortex flow visualization investigation , 1986 .

[17]  Danny R. Hoad.  Helicopter blade-vortex interaction locations: Scale-model acoustics and free-wake analysis results , 1987 .