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| Author | : J. Fitzgerald |
| Publisher | : |
| Total Pages | : 116 |
| Release | : 1988 |
| Genre | : Rotors (Helicopters) |
| ISBN | : |
| Author | : J. Fitzgerald |
| Publisher | : |
| Total Pages | : 158 |
| Release | : 1988 |
| Genre | : Rotors (Helicopters) |
| ISBN | : |
| Author | : J. Fitzgerald |
| Publisher | : |
| Total Pages | : 99 |
| Release | : 1988 |
| Genre | : |
| ISBN | : |
| Author | : |
| Publisher | : |
| Total Pages | : 192 |
| Release | : 1990 |
| Genre | : |
| ISBN | : |
| Author | : J. Fitzgerald |
| Publisher | : |
| Total Pages | : 116 |
| Release | : 1988 |
| Genre | : Rotors (Helicopters) |
| ISBN | : |
| Author | : Danny R. Hoad |
| Publisher | : |
| Total Pages | : 104 |
| Release | : 1986 |
| Genre | : Aerodynamics |
| ISBN | : |
An investigation of helicopter rotor noise at model scale has been conducted in the Langley 4- by 7-Meter Tunnel. Two rotor systems were used in this program to examine the main-rotor-only noise characteristics in preparation for a complete main rotor/tail rotor interaction study. Each rotor system had several tip configurations in order to select at least one appropriate configuration to use for the main and tail rotor tests. The rotor systems were tested at various operating conditions particularly designed to evaluate the acoustic characteristics of each rotor/tip configuration. Both acoustic and aerodynamic data were acquired during this test; however, only aerodynamic data are presented herein. The acoustic data have been reported elsewhere and properly referenced within.
| Author | : |
| Publisher | : |
| Total Pages | : 224 |
| Release | : 1984 |
| Genre | : |
| ISBN | : |
| Author | : National Aeronautics and Space Administration (NASA) |
| Publisher | : Createspace Independent Publishing Platform |
| Total Pages | : 192 |
| Release | : 2018-07-17 |
| Genre | : |
| ISBN | : 9781722910808 |
The rotor broadband noise mechanisms considered are the following: (1) lift fluctuation due to turbulence ingestion; (2) boundary layer/trailing edge interaction; (3) tip vortex formation; and (4) turbulent vortex shedding from blunt trailing edge. Predictions show good agreement with available experimental data. The study shows that inflow turbulence is the most important broadband noise source for typical helicopters' main rotors at low- and mid-frequencies. Due to the size difference, isolated helicopter tail rotor broadband noise is not important compared to the much louder main rotor broadband noise. However, the inflow turbulence noise from a tail rotor can be very significant because it is operating in a highly turbulent environment, ingesting wakes from upstream components of the helicopter. The study indicates that the main rotor turbulent wake is the most important source of tail rotor broadband noise. The harmonic noise due to ingestion of main rotor tip vortices is studied. Chou, Shau-Tak Rudy Unspecified Center AERODYNAMIC NOISE; AIRCRAFT NOISE; BROADBAND; HELICOPTER TAIL ROTORS; HELICOPTERS; NOISE GENERATORS; ROTARY WINGS; ROTOR AERODYNAMICS; BLUNT TRAILING EDGES; HARMONIC OSCILLATION; NOISE PREDICTION (AIRCRAFT); TURBULENT WAKES; VORTEX SHEDDING; VORTICES...
| Author | : P. F. Sheridan |
| Publisher | : |
| Total Pages | : 162 |
| Release | : 1984 |
| Genre | : |
| ISBN | : |
An experimental investigation was conducted at the Boeing 20-ft x 20-ft VSTOL wind tunnel to study the aerodynamic interactions of the main rotor and tail rotor of a single rotor helicopter in ground effect. The model used for this test was the YUH-61A UTTAS at a scale of 1/4.85 with both rotors operated at full scale tip speed. A comprehensive array of parametric data was obtained to examine the interactions between main rotor/tail, rotor/fin, and main rotor/fin for various wind azimuths and airspeeds. Extensive flow visualization records were taken to define the flow mechanisms involved. In addition, quantitative data of the flow characteristics were provided by hot film measurements. Tests were conducted at the four principal wind azimuths of 0, +90, 180, -90 degrees. Parametric sweeps of airspeed, main rotor thrust, and tail rotor thrust were studied at each yaw condition. Limited investigations of the effects of varying fin size and height above the ground supplemented the parametric sweeps for the right sideward and rearward flight conditions. The effects of tail rotor placement were also investigated for the tail rotor power critical flight condition of 35 knots sideward to the right.
| Author | : |
| Publisher | : |
| Total Pages | : 352 |
| Release | : 1983 |
| Genre | : |
| ISBN | : |
