Prediction of Unsteady Airloads for Oblique Blade-Gust Interaction in Compressible Flow

Chu, S. S.

doi:10.2514/3.49458

Cited by 8 publications

(2 citation statements)

References 6 publications

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“…Thus for loading noise of a fan, with "1, these factors are (1/ , M/ , 1/ , 1/ ), and for blade}vortex interaction, with "M, they are (M/ , M/ , M/ , M/ ). In the aeroacoustic literature, e.g., references [4,5], a common choice of variables is equivalent to taking " , for which the factors are (1, M/ , 1/ , 1). The dependence of ampli"cation on frequency is of particular interest.…”

Section: Introductionmentioning

confidence: 99%

Similarity Variables for Sound Radiation in a Uniform Flow

Chapman

2000

Journal of Sound and Vibration

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Section: Introductionmentioning

confidence: 99%

Similarity Variables for Sound Radiation in a Uniform Flow

Chapman

2000

Journal of Sound and Vibration

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“…While the above approaches mostly concern airfoil-gust interactions and are essentially twodimensional in nature, Widnall and Chu [30] and later Martinez and Widnall [31] attempted the development of a theoretical model for the interaction of an infinite wing with an oblique gust.…”

Section: Unsteady Aerodynamicsmentioning

confidence: 99%

A New Experimental Approach to Study Helicopter Blade-Vortex Interaction Noise

Koushik

2008

14th AIAA/CEAS Aeroacoustics Conference (29th AIAA Aeroacoustics Conference)

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A unique and novel experimental approach has been developed to study the aerodynamics and acoustics of the helicopter Blade-Vortex Interaction in a controlled hover environment. This is achieved by having a non-lifting single-bladed rotor with a rigid hub interact with a carefully controlled gust disturbance that replicates the essential characteristics of the vortex velocity. This experimental approach termed the Blade-Controlled Disturbance-Interaction or the BCDI, decouples the rotor parameters from the charactersitics of the incident disturbance velocity, thus providing an ideal setup for studying the blade's aerodynamics and acoustic response in detail. Moreover, the angle of interaction between the disturbance field and the rotor blade can be controlled by orienting the gust, providing the ability to study both parallel and oblique interactions. The noise data was recorded at thirty different microphone locations.A series of experiments at various rotor tip Mach numbers and interaction angles, replicating many of the conditions of helicopter BVI, were performed. The results show that the the directionality of the BVI noise is strongly determined by the interaction angle. A small change in interaction angle results in the radiation of noise over a larger azimuthal area compared to the parallel interaction. Moreover, as the interaction becomes more oblique, the peak noise elevation angle approaches closer to the rotor plane.A linear unsteady lifting-line aerodynamic theory (corrected for chord-wise non-compactness )was used to estimate the blade aerodynamics during the interaction and hence the radiated noise.Although the theory under-predicted the noise levels for most of the cases, and did not replicate exactly the general pulse shape, the general directionality trends were predicted reasonably well.The theory was used to separate the contribution to the acoustics, from different spanwise blade sections, providing significant insights into the phasing mechanism of BVI noise.

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Noncavitating Lifting Sections

Blake¹

2017

Mechanics of Flow-Induced Sound and Vibration, Volume 2

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Prediction of Unsteady Airloads for Oblique Blade-Gust Interaction in Compressible Flow

Cited by 8 publications

References 6 publications

Similarity Variables for Sound Radiation in a Uniform Flow

Similarity Variables for Sound Radiation in a Uniform Flow

A New Experimental Approach to Study Helicopter Blade-Vortex Interaction Noise

Noncavitating Lifting Sections

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