Effect of tip vortex structure on helicopter noise due to blade-vortex interaction | Zendy

Sheila E. Widnall | Zendy; Thomas L. Wolf | Zendy

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Effect of tip vortex structure on helicopter noise due to blade-vortex interaction

Author(s) -

Sheila E. Widnall,

Thomas L. Wolf

Publication year - 1980

Publication title -

journal of aircraft

Language(s) - English

Resource type - Journals

SCImago Journal Rank - 0.64

H-Index - 94

eISSN - 1533-3868

pISSN - 0021-8669

DOI - 10.2514/3.44681

Subject(s) - vortex , lift (data mining) , helicopter rotor , physics , aerodynamics , mechanics , acoustics , blade (archaeology) , inviscid flow , starting vortex , noise (video) , lift coefficient , horseshoe vortex , vortex shedding , structural engineering , vortex ring , engineering , vibration , turbulence , computer science , image (mathematics) , artificial intelligence , reynolds number , data mining

A potential cause of helicopter impulsive noise, commonly called blade slap, is the unsteady lift fluctuation on a rotor blade due to interaction with the vortex trailed from another blade. The relationship between vortex structure and the intensity of the acoustic signal is investigated. The analysis is based on a theoretical model for blade/vortex interaction. Unsteady lift on the blades due to blade/vortex interaction is calculated using linear unsteady aerodynamic theory, and expressions are derived for the directivity, frequency spectrum, and transient signal of the radiated noise. An inviscid rollup model is used to calculate the velocity profile in the trailing vortex from the spanwise distribution of blade tip loading. A few cases of tip loading are investigated, and numerical results are presented for the unsteady lift and acoustic signal due to blade/vortex interaction. The intensity of the acoustic signal is shown to be quite sensitive to changes in tip vortex structure.

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