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  • 1
    Publication Date: 2018-12-01
    Description: Blade-vortex interaction (BVI) is the source mechanism for a prominent impulsive noise created by rotorcraft. An experimental study of two dimensional BVI, a simplified case representing the most intense and impulsive noise generation condition, was performed to explore the fundamental physics associated with the blade-vortex interaction process. The purpose of this paper is to report cumulative results from this experimental study. 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. The blade involved undergoes significant transient loading. The effects of the interaction process on the blade and the vortex are shown to be increased by both reduction of blade-to-vortex spacing and increase in blade loading. Calculations of the acoustic field produced by the interaction using measured unsteady blade surface pressure data are presented and show acoustic waveforms similar to those obtained from model helicopter acoustic tests.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 87-2745
    Format: text
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  • 2
    Publication Date: 2018-12-01
    Description: Blade-vortex interaction occurs when a rotor blade encounters the tip vortex from a previous rotor blade. To obtain details of the close encounter process, the results from a flow visualization study of an airfoil representing a rotor blade in the wake of an oscillating airfoil serving as a vortex generator are described. A distinguishing feature of this study is that the vortex filament is oriented parallel to the blade span, orthogonal to the test section free stream velocity. This orientation simulates the case of two-dimensional blade-vortex interaction, which is known to produce the most impulsive and most intensive BVI noise. Photographic data are examined to deduce qualitative and quantitative details of the close encounter interaction process with emphasis on structural changes in the vortex filament and its trajectory.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 84-2307
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  • 3
    Publication Date: 2018-12-01
    Description: Unsteady blade surface pressures were measured during two-dimensional blade-vortex interaction. A periodically generated vortex filament interacted with a blade model instrumented over the first 20 percent of the blade surface. Analysis of data confirm the leading edge nature of BVI and show the amplitude of the interaction to be a strong function of blade-to-vortex spacing. Lift perturbation time histories were computed and are used to examine details of the encounter process.
    Keywords: ACOUSTICS
    Type: AIAA PAPER 86-1856
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  • 4
    Publication Date: 2011-08-19
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 24; 1468-147
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