A New Experimental Approach To Study Helicopter Blade Vortex Interaction Noise
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Acoustic Measurements from a Rotor Blade-vortex Interaction Noise Experiment in the German-Dutch Wind Tunnel (DNW)
Author | : Ruth McVoy Martin |
Publisher | : |
Total Pages | : 188 |
Release | : 1988 |
Genre | : Rotors (Helicopters) |
ISBN | : |
Acoustic data are presented from a 40-percent-scale model of the four-bladed BO-105 helicopter main rotor, tested in a large aeroacoustic wind tunnel. Rotor blade-vortex interaction (BVI) noise data in the low-speed flight range were acquired using a traversing in-flow microphone array. The experimental apparatus, testing procedures, calibration results, and experimental objectives are fully described. A large representative set of averaged acoustic signals are presented.
Helicopter Impulsive Noise: Theoretical and Experimental Status
Author | : F. H. Schmitz |
Publisher | : |
Total Pages | : 110 |
Release | : 1983 |
Genre | : |
ISBN | : |
The theoretical and experimental status of helicopter impulsive noise is reviewed. The two major source mechanisms of helicopter impulsive noise are addressed: high-speed impulsive noise and blade-vortex interaction impulsive noise. A thorough physical explanation of both generating mechanisms is presented together with model and full-scale measurements of the phenomena. Current theoretical prediction methods are compared with experimental findings of isolated rotor tests. The noise generating mechanisms of high speed impulsive noise are fairly well understood - theory and experiment compare nicely over Mach number ranges typical of today's helicopters. For the case of blade-vortex interaction noise, understanding of noise generating mechanisms and theoretical comparison with experiment are less satisfactory. Several methods for improving theory-experiment are suggested.
An Experimental Study of Rotor Blade-vortex Interaction
Author | : Makam Surendraiah |
Publisher | : |
Total Pages | : 60 |
Release | : 1970 |
Genre | : Rotors (Helicopters) |
ISBN | : |
Helicopter Blade-Vortex Interaction Noise with Comparisons to Cfd Calculations
Author | : National Aeronautics and Space Administration (NASA) |
Publisher | : Createspace Independent Publishing Platform |
Total Pages | : 60 |
Release | : 2018-07-08 |
Genre | : |
ISBN | : 9781722428778 |
A comparison of experimental acoustics data and computational predictions was performed for a helicopter rotor blade interacting with a parallel vortex. The experiment was designed to examine the aerodynamics and acoustics of parallel Blade-Vortex Interaction (BVI) and was performed in the Ames Research Center (ARC) 80- by 120-Foot Subsonic Wind Tunnel. An independently generated vortex interacted with a small-scale, nonlifting helicopter rotor at the 180 deg azimuth angle to create the interaction in a controlled environment. Computational Fluid Dynamics (CFD) was used to calculate near-field pressure time histories. The CFD code, called Transonic Unsteady Rotor Navier-Stokes (TURNS), was used to make comparisons with the acoustic pressure measurement at two microphone locations and several test conditions. The test conditions examined included hover tip Mach numbers of 0.6 and 0.7, advance ratio of 0.2, positive and negative vortex rotation, and the vortex passing above and below the rotor blade by 0.25 rotor chords. The results show that the CFD qualitatively predicts the acoustic characteristics very well, but quantitatively overpredicts the peak-to-peak sound pressure level by 15 percent in most cases. There also exists a discrepancy in the phasing (about 4 deg) of the BVI event in some cases. Additional calculations were performed to examine the effects of vortex strength, thickness, time accuracy, and directionality. This study validates the TURNS code for prediction of near-field acoustic pressures of controlled parallel BVI. McCluer, Megan S. Ames Research Center...
New Computational Methods for the Prediction and Analysis of Helicopter Noise
Author | : Roger C. Strawn |
Publisher | : |
Total Pages | : 18 |
Release | : 1996 |
Genre | : Fluid dynamics |
ISBN | : |
Abstract: "This paper describes several new methods to predict and analyze rotorcraft noise. These methods are: 1) a combined computational fluid dynamics and Kirchhoff scheme for far-field noise predictions, 2) parallel computer implementation of the Kirchhoff integrations, 3) audio and visual rendering of the computed acoustic predictions over large far-field regions, and 4) acoustic tracebacks to the Kirchhoff surface to pinpoint the sources of the rotor noise. The paper describes each method and presents sample results for three test cases. The first case consists of in-plane high-speed impulsive noise and the other two cases show idealized parallel and oblique blade-vortex interactions. The computed results show good agreement with available experimental data but convey much more information about the far-field noise propagation. When taken together, these new analysis methods exploit the power of new computer technologies and offer the potential to significantly improve our prediction and understanding of rotorcraft noise."