A THEORY FOR PREDICTING THE ROTATIONAL NOISE OF LIFTING ROTORS IN FORWARD FLIGHT, INCLUDING A COMPARISON WITH EXPERIMENT

Abstract

A theory and resultant calculations are presented, predicting the noise generated by a lifting rotor in forward flight. With suitable adjustments in parameters, this theory reproduced (by numerical integration) the closed form results of Garrick and Watkins in their investigation of noise produced by a propeller. The theory presented here accounts for (1) asymmetry of inflow, lift, and drag; (2) non-linear section characteristics, compressibility, and reverse flow; (3) first harmonic and steady rigid blade flapping and pitching; (4) rotor shaft tilt; and (5) chordwise distribution of lift and drag forces. Sound pressure levels were evaluated for up to 20 harmonics at a general field point translating with the rotor hub, for the H-34 and HU-1 helicopters. A comparison with experiment is also presented.

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Document Details

Document Type
Technical Report
Publication Date
Jan 01, 1966
Accession Number
AD0629646

Entities

People

  • Lawrence R. Sutton
  • Robert G. Loewy

Tags

Communities of Interest

  • Air Platforms

DTIC Thesaurus Topics

  • Aircrafts
  • Airframes
  • Army Aviation
  • Axial Flow
  • Boundary Layer
  • Contracts
  • Coordinate Systems
  • Far Field
  • Fourier Series
  • Frequency
  • Leading Edges
  • Mach Number
  • Measurement
  • Pressure Distribution
  • Propeller Noise
  • Tail Rotors
  • Two Dimensional

Fields of Study

  • Physics

Readers

  • Aerodynamics.
  • Calculus or Mathematical Analysis