Helicopter Model Rotor-Blade Vortex Interaction Impulsive Noise: Scalability and Parametric Variations

Abstract

Acoustic data taken in the anechoic Deutsch-NIederlaendischer Windkanal (DNW) have documented the blade-vortex interaction (BVI) impulsive noise radiated from 1/7-scale model main rotor of the AH-1 series helicopter. Average model-scale data were compared with averaged full-scale, in-flight acoustic data under similar nondimensional test conditions. At low advance ratios (mu = 0.164-0.194), the data scale remarkably well in level and waveform shape, and also duplicate the directivity pattern of BVI impulsive noise. At moderate advance ratios (mu = 0.224-0.270), the scaling deteriorates, suggesting that the model-scale rotor is not adequately simulating the full-scale BVI noise; presently, no proved explanation of this discrepancy exists. Carefully performed parametric variations over a complete matrix of testing conditions have shown that all of the four governing nondimensional parameters -- tip Mach number at hover, advance ratio, local inflow ratio, and thrust coefficient -- are highly sensitive to BVI noise radiation. Keywords: Helicopter noise; Blade vortex interaction; Measured acoustics.

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Document Details

Document Type
Technical Report
Publication Date
Dec 01, 1984
Accession Number
ADA159471

Entities

People

  • D. A. Boxwell
  • F. H. Schmitz
  • K. J. Schultz
  • W. R. Splettstoesser

Organizations

  • National Aeronautics and Space Administration

Tags

DTIC Thesaurus Topics

  • Acoustic Measurement
  • Acoustic Waves
  • Acoustics
  • Aircrafts
  • Airframes
  • Environment
  • Far Field
  • Fixed Wing Aircraft
  • Flight
  • Frequency
  • Mach Number
  • Measurement
  • Radiated Noise
  • Tail Rotors
  • Transducers
  • Turbulent Mixing
  • Wind Tunnels

Fields of Study

  • Physics

Readers

  • Acoustics.
  • Aerodynamics.
  • Aerospace Engineering