Evaluation of helicopter noise due to blade-vortex interaction for five tip configurations

by Danny R Hoad

Publisher: National Aeronautics and Space Administration, Scientific and Technical Information Branch, Publisher: For sale by the National Technical Information Service] in Washington, D.C, [Springfield, Va

Written in English
Published: Pages: 77 Downloads: 136
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  • Acoustical engineering

Edition Notes

StatementDanny R. Hoad
SeriesAVRADCOM technical report -- 80-B1, NASA technical paper -- 1608
ContributionsUnited States. National Aeronautics and Space Administration. Scientific and Technical Information Branch, Army Research and Technology Laboratories (U.S.). Structures Laboratory, Langley Research Center
The Physical Object
Pagination77 p. :
Number of Pages77
ID Numbers
Open LibraryOL14932613M

Noise Diagnostic Evaluation of Jet Noise Sup-pression Mechanisms C Simple Method for Prediction of Aircraft Noise Contours C Airframe Noise Measurements on a Super-sonic Transport Small-Scale Model C Effect of Tip Vortex Structure on Helicopter Noise Due to Blade-Vortex Interaction C Interior Noise Studies for Single. Summary. Aerodynamic research relating to modern helicopters includes the study of three-dimensional, unsteady, nonlinear flow fields. A selective review is made of some of the phenomena that hamper the development of satisfactory engineering prediction techniques, but which provide a rich source of research opportunities: flow separation, compressibility effects, complex vortical wakes, and. “Helicopter Noise” to Working Group 1 (WG1, Noise Technical) which included a specific remit to the WG1 Technology Task Group (TTG) to review advancements in helicopter noise technology. The SG remit to WG1 and TTG for CAEP/10 Task N Helicopter Noise is detailed in CAEP-SG/SD/5 . The noise data was recorded at thirty different microphone locations. A series of experiments at various rotor tip Mach numbers and interaction angles, replicat- ing many of the conditions of helicopter BVI, were performed. The results show that the the directionality of the BVI noise is strongly determined by the interaction angle.

टिप आकार में भिन्नता Evaluation of Helicopter Noise Due to Blade-vortex Interaction for Five Tip Configurations को डैनी आर। होड द्वारा NASA पेपर Evaluation of Helicopter Noise Due to Blade-vortex Interaction for Five Tip Configurations. Acoustic data are presented from a percent-scale model of the four-bladed BO 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. Noise transmission loss of aircraft panels using acoustic intensity methods / Advancing-side directivity and retreating-side interactions of model rotor blade-vortex interaction noise / (Washington, Power cepstrum technique with application to model helicopter acoustic data / (Washington. A framework for using continuous wavelet transforms to isolate and extract blade–vortex interaction noise from helicopter acoustic signals is described. The extraction method allows for the investigation of blade–vortex interactions independent of other sound sources.

  The helicopter’s unique sound, created by blade vortex interaction, causes people to rate its sound level as much as 10 dB’s higher than it actually registers, doubling the noise impact. This would place perceived helicopter noise at around 97 dB, or a whopping 30 dB’s over the generally accepted noise level of residential areas. This noise results from the interactions of rotor blades with the shed vortex trails generated by the tips of the rotor blades. BVI noise has an highly impulsive nature and generates very directional noise pulses below the rotor plane. Other Noise. Other contributors of helicopter noise include engine and gearbox noise. BLADE VORTEX INTERACTION RESEARCH IN THE By FOOT TUNNEL Objectives. Experimentally simulate the aerodynamics and acoustics of parallel (2-D), unsteady helicopter rotor blade-vortex interactions, in a manner closely matching the simplified computational models frequently used for numerical simulations. In case of helicopters, sources of noise are multiple. They are: * Rotor noise or Aerodynamic noise * Engine noise * Transmission noise Aerodynamic noise may be defined as sound which is generated as a direct result of relative motion between a so.

Evaluation of helicopter noise due to blade-vortex interaction for five tip configurations by Danny R Hoad Download PDF EPUB FB2

Evaluation of Helicopter Noise Due to Blade-Vortex Interaction for Five Tip Configurations Danny R. Hoad Structures Luboratory, AVRADCOM Research utrd Techuology Laboratories Langley Research Cezrter Hampton, Virgirria National Aeronautics and Space Administration Scientific and Technical Information Branch Evaluation of helicopter noise due to blade-vortex interaction for five tip configurations.

Washington, D.C.: National Aeronautics and Space Administration, Scientific and Technical Information Branch ; [Springfield, Va.: For sale by the National Technical Information. A study is made of helicopter tail rotor noise, particularly that due to the interactions with main rotor tip vortices.

This report summarizes the present analysis, the computer codes, and the results of several test cases. Amiet's unsteady thin aufoil theory is used to calculate the acoustics of blade-vortex interaction.

The generation of impulsive sound, commonly called blade slap, due to blade‐vortex interaction for helicopter rotors is discussed. The unsteady lift on the blades is calculated using linear unsteady aerodynamic theory for an oblique gust model of the blade‐vortex interaction.

A theoretical model for the radiated sound due to the transient lift fluctuations is by: Evaluation of helicopter noise due to b blade-vortex interaction for five tip configurations.

By D. Hoad. A detailed acoustic evaluation on the same rotor system of the relative applicability of the various tip configurations for blade slap noise reduction is providedAuthor: D.

Hoad. Effect of tip vortex structure on helicopter noise due to blade-vortex interaction. Icing Effect on the Aeroacoustics of Helicopter Blade-Vortex Interaction: A Numerical Study Using Large-Eddy Simulation Effect of the Blade Inner-Tip Position on the Generation of Twin Vortices.

Jiyoung Jung. The effects of helicopter main rotor blade tip modifications on Blade-Vortex Interaction noise at a specific flight c ondition (HART -II Test Case) are studied, results and remarks are presented. The low tip speed of the nose-mounted propeller, a quiet belt-drive system, and a large muffler make the YO-3A a low-noise aircraft well suited for measuring in- flight helicopter noise.

The YO-3A carries a pilot and flight engineer and is equipped with instrumentation for acoustic and flight condition data acquisition. 1 Limiting cases of blade vortex interaction 2 Stages in develoment of tip vortex 3 Flow visualization during the vortex body interaction 4 Spectrum for helicopter 5 Impulsive noise signal.

6 Spectrum of rotational noise (a) with blade vortex interaction (b) with tip vortex eliminated 7 Trajectories of rotating tip. The effect of tip shape modification on blade vortex interaction induced helicopter blade slap noise was investigated.

Simulated flight and descent velocities which have been shown to produce. tunnel demonstrated the potential of active flaps to reduce blade-vortex interaction (BVI) noise over a wide range of directivity angles underneath the advancing rotor disk.

The active flap rotor is a full-scale MD helicopter main rotor with all of its five blades modified to. However, these tip shapes have not been able to substantially reduce blade–vortex interaction noise without degradation of rotor performance.

Meanwhile, blade root control techniques, such as higher-harmonic pitch control (HHC) and individual blade control (IBC) concepts, have been extensively investigated for noise and vibration reduction. OTORCRAFT noise is notoriously obtrusive, especially in low-speed descent flight conditions where heavy blade-vortex interaction (BVI) may be encountered.

Community acceptance issues and military operational detectability concerns are driving research focused on the reduction of helicopter noise, under various flight conditions including the.

Blade–vortex interaction (BVI) noise reduction and modeling have been a major focus of the helicopter rotor aeroacoustics research during the past few decades. The BVI noise is the result of unsteady pressure fluctuations on the blade due to interactions with tip-vortices previously generated.

The unsteady forces include effects from harmonically-varying inflow, from impulsive blade-vortex interaction loading (including transonic effects), and broadband noise due to loading from inflow turbulence and self generated turbulence. The state- of-the-art of predicting noise from practical configurations is assessed.

vortices in order to reduce blade/vortex interaction noise resulted in the fabrication and wind tunnel testing of a model rotor which confirmed that useful noise reduc-tions can indeed be obtained in this way. In order to support the evaluation of vane tip designs, a computer program currently used to generate rotor loads for acoustic.

Reducing the noise that creates from helicopter rotor blades, tail rotors, engine etc. is a one step closer to this crisis.

Helicopter noise reduction is a topic of research into designing helicopters which can be operated more quietly. The major source of the noise come from the rotor blade vortex interaction. Helicopter Noise due to Blade-Vortex Interaction “Helicopter Rotor Tip Shapes for Reduced Blade–Vortex Interaction an Experimental Investigation,” AIAA PaperReno, Nevada, Jan.

Brooks, Thomas F., and. Booth, Earl R.,“ The Effects of Higher Harmonic Control on Blade–Vortex Interaction Noise and Vibration. This noise mechanism depends strongly on the helicopter flight conditions and the relative location and phasing of the main and tail rotors.

fluctuations of significant magnitude can be generated by tail rotors due to a series of interactions with main rotor tip vortices. This noise mechanism depends strongly upon the helicopter flight. The aim of this program is to reduce the noise generated by so-called blade-vortex interactions (BVI), which occur when a blade impacts a vortex, created at the tip of the blade of any helicopter.

blade/blade vortex interaction (BVI) noise, main rotor wake/tail rotor interaction (TRI) noise and tail rotor (TR) These changes in noise level will be more marked on higher tip speed rotors simply because the sources are naturally more intense.

From a helicopter noise below the “10 dB down” point is clear to the. That varying the tip shape will affect the BVI and consequently noise, was well known (for example, see the NASA paper Evaluation of Helicopter Noise Due to Blade-vortex Interaction for Five Tip Configurations by Danny R.

Hoad, which compares the sound produced by various tip shapes). However, with the advances in computer modeling and CFD, a number of modern helicopters incorporate blade tips. Blade-Vortex Interaction (BVI) is one such mechanism of rotor noise.

BVI noise is a problem for civilian helicopter terminal area operations because the noise occurs itself primarily in descending flight, with the peak noise signatures occurring near the standard 6 degree glide path angle on approach.

A low-noise helicopter blade, AT1, was designed with the concept of reducing noise without the drop of rotor performance. In the concept, High-Speed Impulsive (HSI) noise is reduced by applying a thin airfoil in the tip region and a dog-tooth like extension in the leading-edge of the tip region.

Helicopter Tail Rotor Orthogonal Blade Vortex Interaction In the case of main rotor perpendicular interactions, the axis of the tip vortex is Apart from performance, the radiated noise from helicopters, both civil and military, has always been a cause for concern.

In. Additional sources, such as Blade Vortex Interaction (BVI) noise and High Speed Impulsive (HSI) noise, become dominant in specific operating regimes, namely in descents and at high forward.

The rotor wake is a factor in almost all helicopter problems. A major issue in advanced aerodynamic methods is how the wake can be included. Wake formation must at some level be considered a viscous phenomenon, and the helical geometry of the helicopter wake means that the detailed structure is important even at scales on the order of the rotor.

Blade-vortex interaction noise is caused when a rotor blade passes close to the shed tip vortices of a previous blade. This causes a rapid change in the loading of the blade and generates a highly directional impulsive loading noise. BVI noise can occur on either the advancing or.

The high noise levels in helicopter descent flight operations as well as maneuvers are caused by an impulsive noise-generating mechanism known as blade-vortex interaction (BVI) that results from the close proximity between a helicopter’s main rotor blades and.

Helicopter noise reduction is a topic of research into designing helicopters which can be operated more quietly, reducing the public-relations problems with night-flying or expanding an airport.

In addition, it is useful for military applications in which stealth is required: long-range propagation of helicopter noise can alert an enemy to an incoming helicopter in time to re-orient defenses.

Title of dissertation: A New Experimental Approach to Study Helicopter Blade-Vortex Interaction Noise Sudarshan N. Koushik, Doctor of Philosophy, Dissertation directed by: Professor Fredric H.

Schmitz Department of Aerospace Engineering A unique and novel experimental approach has been developed to study the aerodynamics and.Helicopter Noise - Volume 69 Issue - I. M. Davidson, T. J. Harcest. Nowhere in the literature of helicopter noise can one find a general understanding; only isolated, inconsistent, and often inadequately documented facts.blade with the blade tip vortex is called Blade-Vortex Interaction (BVI) noise.

This is the recognizable “flapping” noise of a helicopter. BVI noise is most noticeable when the helicopter descends gently to land.

The blade tip vortex moves downward during normal flight. But during an .