Author
F. H. Schmitz
Bio: F. H. Schmitz is an academic researcher from Ames Research Center. The author has contributed to research in topics: Noise & Aircraft noise. The author has an hindex of 2, co-authored 2 publications receiving 134 citations.
Topics: Noise, Aircraft noise, Impulse noise
Papers
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TL;DR: The theoretical and experimental status of helicopter impulsive noise is reviewed in this article, where two major sources of helicopter noise are addressed: high-speed impulsive noises and blade- vortex interaction noise.
129 citations
01 Nov 1983
TL;DR: The theoretical and experimental status of helicopter impulsive noise is reviewed in this paper, where the two major source mechanisms of helicopter noise are addressed: high-speed impulsive noises and blade- vortex interaction noise.
Abstract: 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.
11 citations
Cited by
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TL;DR: In this article, the Kirchhoff formulation for moving surfaces is compared with the Ffowcs Williams Hawkings (FW-H) equation for the prediction of high-speed impulsive noise, in an effort to eliminate the need to compute the quadrupole contribution.
420 citations
Book•
01 Jan 2001
TL;DR: The second edition of Helicopter Dynamics by A.R. Bramwell as mentioned in this paper provides a detailed summary of helicopter aerodynamics, stability, control, structural dynamics, vibration, and aeroelastic and aeromechanical stability.
Abstract: Since the original publication of Helicopter Dynamics by A.R.S. Bramwell in 1976, this book has become the definitive text on helicopter dynamics. As such it is an essential aid to those studying the behavior of helicopters. The second edition builds on the strengths of the original, and hence the approach of the first edition is retained. The authors provide a detailed summary of helicopter aerodynamics, stability, control, structural dynamics, vibration, and aeroelastic and aeromechanical stability.
315 citations
01 Nov 1991
TL;DR: A NACA 0015 semispan wing was placed in a low-speed wind tunnel, and measurements were made of the pressure on the upper and lower surface of the wing and of velocity across the vortex trailing downstream from the tip of a wing.
Abstract: A NACA 0015 semispan wing was placed in a low-speed wind tunnel, and measurements were made of the pressure on the upper and lower surface of the wing and of velocity across the vortex trailing downstream from the tip of the wing. Pressure data were obtained for both 2-D and 3-D configurations. These data feature a detailed comparison between wing tips with square and round lateral edges. A two-component laser velocimeter was used to measure velocity profiles across the vortex at numerous stations behind the wing and for various combinations of conditions. These conditions include three aspect ratios, three chord lengths, a square- and a round lateral-tip, presence or absence of a boundary-layer trip, and three image plane positions located opposite the wing tip. Both pressure and velocity measurements were made for the angles of attack 4 deg less than or equal to alpha less than or equal to 12 deg and for Reynolds numbers 1 x 10(exp 6) less than or equal to Re less than or equal to 3 x 10(exp 6).
165 citations
TL;DR: In this paper, the authors investigated different design concepts to reduce the blade-tip interaction noise and vibration by diffusing tip vortices, but these tip shapes have not been able to substantially reduce blade-vortex interaction noise without degradation of rotor performance.
141 citations
TL;DR: In this article, a detailed analysis of the complex vortical wakes generated by helicopter rotors is presented by means of several examples, including blade/vortex interactions, vortex perturbations, wake instabilities, and vortex/surface interaction phenomena.
Abstract: Many experimental challenges are encountered when attempting to understand the complex vortical wakes generated by helicopter rotors. The problems are illustrated by means of several examples, including blade/vortex interactions, vortex perturbations, wake instabilities, and vortex/surface interaction phenomena. Specific emphasis is placed on flow visualization and quantitative measurements using laser Doppler velocimetry
88 citations