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Sample records for airframe noise prediction

  1. Predicted airframe noise levels

    NASA Technical Reports Server (NTRS)

    Raney, J. P.

    1980-01-01

    Calculated values of airframe noise levels corresponding to FAA noise certification conditions for six aircraft are presented. The aircraft are: DC-9-30; Boeing 727-200; A300-B2 Airbus; Lockheed L-1011; DC-10-10; and Boeing 747-200B. The prediction methodology employed is described and discussed.

  2. Airframe Noise Prediction by Acoustic Analogy: Revisited

    NASA Technical Reports Server (NTRS)

    Farassat, F.; Casper, Jay H.; Tinetti, A.; Dunn, M. H.

    2006-01-01

    The present work follows a recent survey of airframe noise prediction methodologies. In that survey, Lighthill s acoustic analogy was identified as the most prominent analytical basis for current approaches to airframe noise research. Within this approach, a problem is typically modeled with the Ffowcs Williams and Hawkings (FW-H) equation, for which a geometry-independent solution is obtained by means of the use of the free-space Green function (FSGF). Nonetheless, the aeroacoustic literature would suggest some interest in the use of tailored or exact Green s function (EGF) for aerodynamic noise problems involving solid boundaries, in particular, for trailing edge (TE) noise. A study of possible applications of EGF for prediction of broadband noise from turbulent flow over an airfoil surface and the TE is, therefore, the primary topic of the present work. Typically, the applications of EGF in the literature have been limited to TE noise prediction at low Mach numbers assuming that the normal derivative of the pressure vanishes on the airfoil surface. To extend the application of EGF to higher Mach numbers, the uniqueness of the solution of the wave equation when either the Dirichlet or the Neumann boundary condition (BC) is specified on a deformable surface in motion. The solution of Lighthill s equation with either the Dirichlet or the Neumann BC is given for such a surface using EGFs. These solutions involve both surface and volume integrals just like the solution of FW-H equation using FSGF. Insight drawn from this analysis is evoked to discuss the potential application of EGF to broadband noise prediction. It appears that the use of a EGF offers distinct advantages for predicting TE noise of an airfoil when the normal pressure gradient vanishes on the airfoil surface. It is argued that such an approach may also apply to an airfoil in motion. However, for the prediction of broadband noise not directly associated with a trailing edge, the use of EGF does not

  3. Airframe Noise Prediction Using the Sngr Method

    NASA Astrophysics Data System (ADS)

    Chen, Rongqian; Wu, Yizhao; Xia, Jian

    In this paper, the Stochastic Noise Generation and Radiation method (SNGR) is used to predict airframe noise. The SNGR method combines a stochastic model with Computational Fluid Dynamics (CFD), and it can give acceptable noise results while the computation cost is relatively low. In the method, the time-averaged mean flow field is firstly obtained by solving Reynolds Averaged Navier-Stokes equations (RANS), and a stochastic velocity is generated based on the obtained information. Then the turbulent field is used to generate the source for the Acoustic Perturbation Equations (APEs) that simulate the noise propagation. For numerical methods, timeaveraged RANS equations are solved by finite volume method, and the turbulent model is K - ɛ model; APEs are solved by finite difference method, and the numerical scheme is the Dispersion-Relation-Preserving (DRP) scheme, with explicit optimized 5-stage Rung-Kutta scheme time step. In order to test the APE solver, propagation of a Gaussian pulse in a uniform mean flow is firstly simulated and compared with the analytical solution. Then, using the method, the trailing edge noise of NACA0012 airfoil is calculated. The results are compared with reference data, and good agreements are demonstrated.

  4. Airframe noise

    NASA Astrophysics Data System (ADS)

    Crighton, David G.

    1991-08-01

    Current understanding of airframe noise was reviewed as represented by experiment at model and full scale, by theoretical modeling, and by empirical correlation models. The principal component sources are associated with the trailing edges of wing and tail, deflected trailing edge flaps, flap side edges, leading edge flaps or slats, undercarriage gear elements, gear wheel wells, fuselage and wing boundary layers, and panel vibration, together with many minor protrusions like radio antennas and air conditioning intakes which may contribute significantly to perceived noise. There are also possibilities for interactions between the various mechanisms. With current engine technology, the principal airframe noise mechanisms dominate only at low frequencies, typically less than 1 kHz and often much lower, but further reduction of turbomachinery noise in particular may make airframe noise the principal element of approach noise at frequencies in the sensitive range.

  5. Modeling for Airframe Noise Prediction Using Vortex Methods

    NASA Astrophysics Data System (ADS)

    Zheng, Z. Charlie

    2002-12-01

    Various components of the airframe are known to be a significant source of noise. With the advent of technology in quieting modern engines, airframe generated noise competes and, in certain instances, surpasses the engine noise. Airframe noise is most pronounced during aircraft approach when the engines are operating at reduced thrust, and airframe components such as high-lift devices and landing gears are in deployed conditions. Recent experimental studies have reaffirmed that the most significant sources of high-lift noise are from the leading-edge slat and the side edges of flaps. Studies of flow field around these structures have consistently shown that there are complicated unsteady vortical flows such as vortex shedding, secondary vortices and vortex breakdown, which are susceptible to far-field radiated sound. The near-field CFD computational data have been used to calculate the far-field acoustics by employing Ffowcs-Williams/Hawkings equation using Lighthill's analogy. However, because of the limit of current computing capacity, it is very time consuming to generate unsteady Navier-Stokes (N-S) computational data for aeroacoustics. Although the N-S simulations are probably necessary to reveal many complex flow phenomena that are unsteady and fully nonlinear, these simulations are not feasible to be used for parametric design. purposes. The objective of this study is thus to develop theoretical models for airframe noise predictions which have quick turn-around computing time. Since it is known that vorticity is a major mechanism responsible for noise generation on high-lift devices, vortex methods have been chosen as modeling tools. Vortex methods are much faster in comparison with other numerical methods, yet they are able to incorporate nonlinear interactions between vortices. Obviously, as with any theoretical model, assumptions have to be made and justified when such models are used in complex flow. The merit and applicability of the models for

  6. Unstructured CFD and Noise Prediction Methods for Propulsion Airframe Aeroacoustics

    NASA Technical Reports Server (NTRS)

    Pao, S. Paul; Abdol-Hamid, Khaled S.; Campbell, Richard L.; Hunter, Craig A.; Massey, Steven J.; Elmiligui, Alaa A.

    2006-01-01

    Using unstructured mesh CFD methods for Propulsion Airframe Aeroacoustics (PAA) analysis has the distinct advantage of precise and fast computational mesh generation for complex propulsion and airframe integration arrangements that include engine inlet, exhaust nozzles, pylon, wing, flaps, and flap deployment mechanical parts. However, accurate solution values of shear layer velocity, temperature and turbulence are extremely important for evaluating the usually small noise differentials of potential applications to commercial transport aircraft propulsion integration. This paper describes a set of calibration computations for an isolated separate flow bypass ratio five engine nozzle model and the same nozzle system with a pylon. These configurations have measured data along with prior CFD solutions and noise predictions using a proven structured mesh method, which can be used for comparison to the unstructured mesh solutions obtained in this investigation. This numerical investigation utilized the TetrUSS system that includes a Navier-Stokes solver, the associated unstructured mesh generation tools, post-processing utilities, plus some recently added enhancements to the system. New features necessary for this study include the addition of two equation turbulence models to the USM3D code, an h-refinement utility to enhance mesh density in the shear mixing region, and a flow adaptive mesh redistribution method. In addition, a computational procedure was developed to optimize both solution accuracy and mesh economy. Noise predictions were completed using an unstructured mesh version of the JeT3D code.

  7. Towards Full Aircraft Airframe Noise Prediction: Lattice Boltzmann Simulations

    NASA Technical Reports Server (NTRS)

    Khorrami, Mehdi R.; Fares, Ehab; Casalino, Damiano

    2014-01-01

    Computational results for an 18%-scale, semi-span Gulfstream aircraft model are presented. Exa Corporation's lattice Boltzmann PowerFLOW(trademark) solver was used to perform time-dependent simulations of the flow field associated with this high-fidelity aircraft model. The simulations were obtained for free-air at a Mach number of 0.2 with the flap deflected at 39 deg (landing configuration). We focused on accurately predicting the prominent noise sources at the flap tips and main landing gear for the two baseline configurations, namely, landing flap setting without and with gear deployed. Capitalizing on the inherently transient nature of the lattice Boltzmann formulation, the complex time-dependent flow features associated with the flap were resolved very accurately and efficiently. To properly simulate the noise sources over a broad frequency range, the tailored grid was very dense near the flap inboard and outboard tips. Extensive comparison of the computed time-averaged and unsteady surface pressures with wind tunnel measurements showed excellent agreement for the global aerodynamic characteristics and the local flow field at the flap inboard and outboard tips and the main landing gear. In particular, the computed fluctuating surface pressure field for the flap agreed well with the measurements in both amplitude and frequency content, indicating that the prominent airframe noise sources at the tips were captured successfully. Gear-flap interaction effects were remarkably well predicted and were shown to affect only the inboard flap tip, altering the steady and unsteady pressure fields in that region. The simulated farfield noise spectra for both baseline configurations, obtained using a Ffowcs-Williams and Hawkings acoustic analogy approach, were shown to be in close agreement with measured values.

  8. Towards an Airframe Noise Prediction Methodology: Survey of Current Approaches

    NASA Technical Reports Server (NTRS)

    Farassat, Fereidoun; Casper, Jay H.

    2006-01-01

    In this paper, we present a critical survey of the current airframe noise (AFN) prediction methodologies. Four methodologies are recognized. These are the fully analytic method, CFD combined with the acoustic analogy, the semi-empirical method and fully numerical method. It is argued that for the immediate need of the aircraft industry, the semi-empirical method based on recent high quality acoustic database is the best available method. The method based on CFD and the Ffowcs William- Hawkings (FW-H) equation with penetrable data surface (FW-Hpds ) has advanced considerably and much experience has been gained in its use. However, more research is needed in the near future particularly in the area of turbulence simulation. The fully numerical method will take longer to reach maturity. Based on the current trends, it is predicted that this method will eventually develop into the method of choice. Both the turbulence simulation and propagation methods need to develop more for this method to become useful. Nonetheless, the authors propose that the method based on a combination of numerical and analytical techniques, e.g., CFD combined with FW-H equation, should also be worked on. In this effort, the current symbolic algebra software will allow more analytical approaches to be incorporated into AFN prediction methods.

  9. Airframe Noise Studies: Review and Future Direction

    NASA Technical Reports Server (NTRS)

    Rackl, Robert G.; Miller, Gregory; Guo, Yueping; Yamamoto, Kingo

    2005-01-01

    This report contains the following information: 1) a review of airframe noise research performed under NASA's Advanced Subsonic Transport (AST) program up to the year 2000, 2) a comparison of the year 1992 airframe noise predictions with those using a year 2000 baseline, 3) an assessment of various airframe noise reduction concepts as applied to the year 2000 baseline predictions, and 4) prioritized recommendations for future airframe noise reduction work. NASA's Aircraft Noise Prediction Program was the software used for all noise predictions and assessments. For future work, the recommendations for the immediate future focus on the development of design tools sensitive to airframe noise treatment effects and on improving the basic understanding of noise generation by the landing gear as well as on its reduction.

  10. Airframe noise: A design and operating problem

    NASA Technical Reports Server (NTRS)

    Hardin, J. C.

    1976-01-01

    A critical assessment of the state of the art in airframe noise is presented. Full-scale data on the intensity, spectra, and directivity of this noise source are evaluated in light of the comprehensive theory developed by Ffowcs Williams and Hawkings. Vibration of panels on the aircraft is identified as a possible additional source of airframe noise. The present understanding and methods for prediction of other component sources - airfoils, struts, and cavities - are discussed. Operating problems associated with airframe noise as well as potential design methods for airframe noise reduction are identified.

  11. Towards Full Aircraft Airframe Noise Prediction: Detached Eddy Simulations

    NASA Technical Reports Server (NTRS)

    Khorrami, Mehdi R.; Mineck, Raymond E.

    2014-01-01

    Results from a computational study on the aeroacoustic characteristics of an 18%-scale, semi-span Gulf-stream aircraft model are presented in this paper. NASA's FUN3D unstructured compressible Navier-Stokes solver was used to perform steady and unsteady simulations of the flow field associated with this high-fidelity aircraft model. Solutions were obtained for free-air at a Mach number of 0.2 with the flap deflected at 39 deg, with the main gear off and on (the two baseline configurations). Initially, the study focused on accurately predicting the prominent noise sources at both flap tips for the baseline configuration with deployed flap only. Building upon the experience gained from this initial effort, subsequent work involved the full landing configuration with both flap and main landing gear deployed. For the unsteady computations, we capitalized on the Detached Eddy Simulation capability of FUN3D to capture the complex time-dependent flow features associated with the flap and main gear. To resolve the noise sources over a broad frequency range, the tailored grid was very dense near the flap inboard and outboard tips and the region surrounding the gear. Extensive comparison of the computed steady and unsteady surface pressures with wind tunnel measurements showed good agreement for the global aerodynamic characteristics and the local flow field at the flap inboard tip. However, the computed pressure coefficients indicated that a zone of separated flow that forms in the vicinity of the outboard tip is larger in extent along the flap span and chord than measurements suggest. Computed farfield acoustic characteristics from a FW-H integral approach that used the simulated pressures on the model solid surface were in excellent agreement with corresponding measurements.

  12. Airframe-Jet Engine Integration Noise

    NASA Technical Reports Server (NTRS)

    Tam, Christopher; Antcliff, Richard R. (Technical Monitor)

    2003-01-01

    It has been found experimentally that the noise radiated by a jet mounted under the wing of an aircraft exceeds that of the same jet in a stand-alone environment. The increase in noise is referred to as jet engine airframe integration noise. The objectives of the present investigation are, (1) To obtain a better understanding of the physical mechanisms responsible for jet engine airframe integration noise or installation noise. (2) To develop a prediction model for jet engine airframe integration noise. It is known that jet mixing noise consists of two principal components. They are the noise from the large turbulence structures of the jet flow and the noise from the fine scale turbulence. In this investigation, only the effect of jet engine airframe interaction on the fine scale turbulence noise of a jet is studied. The fine scale turbulence noise is the dominant noise component in the sideline direction. Thus we limit out consideration primarily to the sideline.

  13. The Prediction and Analysis of Jet Flows and Scattered Turbulent Mixing Noise about Flight Vehicle Airframes

    NASA Technical Reports Server (NTRS)

    Miller, Steven A. E.

    2014-01-01

    Jet flows interacting with nearby surfaces exhibit a complex behavior in which acoustic and aerodynamic characteristics are altered. The physical understanding and prediction of these characteristics are essential to designing future low noise aircraft. A new approach is created for predicting scattered jet mixing noise that utilizes an acoustic analogy and steady Reynolds-averaged Navier-Stokes solutions. A tailored Green's function accounts for the propagation of mixing noise about the airframe and is calculated numerically using a newly developed ray tracing method. The steady aerodynamic statistics, associated unsteady sound source, and acoustic intensity are examined as jet conditions are varied about a large flat plate. A non-dimensional number is proposed to estimate the effect of the aerodynamic noise source relative to jet operating condition and airframe position.The steady Reynolds-averaged Navier-Stokes solutions, acoustic analogy, tailored Green's function, non-dimensional number, and predicted noise are validated with a wide variety of measurements. The combination of the developed theory, ray tracing method, and careful implementation in a stand-alone computer program result in an approach that is more first principles oriented than alternatives, computationally efficient, and captures the relevant physics of fluid-structure interaction.

  14. The Prediction and Analysis of Jet Flows and Scattered Turbulent Mixing Noise About Flight Vehicle Airframes

    NASA Technical Reports Server (NTRS)

    Miller, Steven A.

    2014-01-01

    Jet flows interacting with nearby surfaces exhibit a complex behavior in which acoustic and aerodynamic characteristics are altered. The physical understanding and prediction of these characteristics are essential to designing future low noise aircraft. A new approach is created for predicting scattered jet mixing noise that utilizes an acoustic analogy and steady Reynolds-averaged Navier-Stokes solutions. A tailored Green's function accounts for the propagation of mixing noise about the air-frame and is calculated numerically using a newly developed ray tracing method. The steady aerodynamic statistics, associated unsteady sound source, and acoustic intensity are examined as jet conditions are varied about a large at plate. A non-dimensional number is proposed to estimate the effect of the aerodynamic noise source relative to jet operating condition and airframe position. The steady Reynolds-averaged Navier-Stokes solutions, acoustic analogy, tailored Green's function, non- dimensional number, and predicted noise are validated with a wide variety of measurements. The combination of the developed theory, ray tracing method, and careful implementation in a stand-alone computer program result in an approach that is more first principles oriented than alternatives, computationally efficient, and captures the relevant physics of fluid-structure interaction.

  15. Airframe noise of the DC-9

    NASA Technical Reports Server (NTRS)

    Bauer, A. B.; Munson, A. G.

    1977-01-01

    Airframe noise measurements are reported for the DC-9-31 aircraft flown at several speeds and with a number of flap, landing gear, and slat extension configurations. The data are corrected for atmospheric attenuation and spherical divergence, and are presented for an overhead position normalized to a 1-meter height. The sound pressure levels are found to vary approximately as the fifth power of flight velocity. Both lift and drag dipoles exist as a significant part of the airframe noise. The data are compared with airframe noise predictions using the drag element and the data analysis methods. Although some of the predictions are very good, further work is needed to refine these methods, particularly for the gear-down and flaps-down configurations.

  16. The Airframe Noise Reduction Challenge

    NASA Technical Reports Server (NTRS)

    Lockhard, David P.; Lilley, Geoffrey M.

    2004-01-01

    The NASA goal of reducing external aircraft noise by 10 dB in the near-term presents the acoustics community with an enormous challenge. This report identifies technologies with the greatest potential to reduce airframe noise. Acoustic and aerodynamic effects will be discussed, along with the likelihood of industry accepting and implementing the different technologies. We investigate the lower bound, defined as noise generated by an aircraft modified with a virtual retrofit capable of eliminating all noise associated with the high lift system and landing gear. However, the airframe noise of an aircraft in this 'clean' configuration would only be about 8 dB quieter on approach than current civil transports. To achieve the NASA goal of 10 dB noise reduction will require that additional noise sources be addressed. Research shows that energy in the turbulent boundary layer of a wing is scattered as it crosses trailing edge. Noise generated by scattering is the dominant noise mechanism on an aircraft flying in the clean configuration. Eliminating scattering would require changes to much of the aircraft, and practical reduction devices have yet to receive serious attention. Evidence suggests that to meet NASA goals in civil aviation noise reduction, we need to employ emerging technologies and improve landing procedures; modified landing patterns and zoning restrictions could help alleviate aircraft noise in communities close to airports.

  17. Airframe Noise Reduction Studies and Clean-Airframe Noise Investigation

    NASA Technical Reports Server (NTRS)

    Fink, M. R.; Bailey, D. A.

    1980-01-01

    Acoustic wind tunnel tests were conducted of a wing model with modified leading edge slat and trailing edge flap. The modifications were intended to reduce the surface pressure response to convected turbulence and thereby reduce the airframe noise without changing the lift at constant incidence. Tests were conducted at 70.7 and 100 m/sec airspeeds, with Reynolds numbers 1.5 x 10 to the 6th power and 2.1 x 10 to the 6th power. Considerable reduction of noise radiation from the side edges of a 40 deflection single slotted flap was achieved by modification to the side edge regions or the leading edge region of the flap panel. Total far field noise was reduced 2 to 3 dB over several octaves of frequency. When these panels were installed as the aft panel of a 40 deg deflection double slotted flap, 2 dB noise reduction was achieved.

  18. Landing approach airframe noise measurements and analysis

    NASA Technical Reports Server (NTRS)

    Lasagna, P. L.; Mackall, K. G.; Burcham, F. W., Jr.; Putnam, T. W.

    1980-01-01

    Flyover measurements of the airframe noise produced by the AeroCommander, JetStar, CV-990, and B-747 airplanes are presented for various landing approach configurations. Empirical and semiempirical techniques are presented to correlate the measured airframe noise with airplane design and aerodynamic parameters. Airframe noise for the jet-powered airplanes in the clean configuration (flaps and gear retracted) was found to be adequately represented by a function of airplane weight and the fifth power of airspeed. Results show the airframe noise for all four aircraft in the landing configuration (flaps extended and gear down) also varied with the fifth power of airspeed, but this noise level could not be represented by the addition of a constant to the equation for clean-configuration airframe noise.

  19. Airframe noise component interaction studies

    NASA Technical Reports Server (NTRS)

    Fink, M. R.; Schlinker, R. H.

    1979-01-01

    Acoustic wind tunnel tests were conducted of a two-dimensional wing section with removable high-lift leading and trailing edge devices and a removeable two-wheel landing gear with open cavity. An array of far field conventional microphones and an acoustic mirror directional microphone were utilized to determine far field spectrum levels and noise source distribution. Data were obtained for the wing with components deployed separately and in various combinations. The basic wing model had 0.305 m (1.00 ft) chord, which is roughly 1/10 scale for a one-hundred passenger transport airplane. Most of the data were obtained at 70.7 and 100 m/sec (232 and 328 ft/sec) airspeeds, which bracket the range of practical approach speeds for such aircraft. Data were obtained at frequence to 40 kHz so that, when scaled to s typical full-airframe, the frequency region which strongly influences preceived noise level would be included.

  20. Simulation-Based Airframe Noise Prediction of a Full-Scale, Full Aircraft

    NASA Technical Reports Server (NTRS)

    Khorrami, Mehdi R.; Fares, Ehab

    2016-01-01

    A previously validated computational approach applied to an 18%-scale, semi-span Gulfstream aircraft model was extended to the full-scale, full-span aircraft in the present investigation. The full-scale flap and main landing gear geometries used in the simulations are nearly identical to those flown on the actual aircraft. The lattice Boltzmann solver PowerFLOW® was used to perform time-accurate predictions of the flow field associated with this aircraft. The simulations were performed at a Mach number of 0.2 with the flap deflected 39 deg. and main landing gear deployed (landing configuration). Special attention was paid to the accurate prediction of major sources of flap tip and main landing gear noise. Computed farfield noise spectra for three selected baseline configurations (flap deflected 39 deg. with and without main gear extended, and flap deflected 0 deg. with gear deployed) are presented. The flap brackets are shown to be important contributors to the farfield noise spectra in the mid- to high-frequency range. Simulated farfield noise spectra for the baseline configurations, obtained using a Ffowcs Williams and Hawkings acoustic analogy approach, were found to be in close agreement with acoustic measurements acquired during the 2006 NASA-Gulfstream joint flight test of the same aircraft.

  1. Airframe self-noise: Four years of research. [aircraft noise reduction for commercial aircraft

    NASA Technical Reports Server (NTRS)

    Hardin, J. C.

    1976-01-01

    A critical assessment of the state of the art in airframe self-noise is presented. Full-scale data on the intensity, spectra and directivity of this noise source are evaluated in the light of the comprehensive theory developed by Ffowcs-Williams and Hawkins. Vibration of panels on commercial aircraft is identified as a possible additional source of airframe noise. The present understanding and methods for prediction of other component sources - airfoils, struts, and cavities - are discussed, and areas for further research as well as potential methods for airframe noise reduction are identified. Finally, the various experimental methods which have been developed for airframe noise research are discussed and sample results are presented.

  2. Simulations & Measurements of Airframe Noise: A BANC Workshops Perspective

    NASA Technical Reports Server (NTRS)

    Choudhari, Meelan; Lockard, David

    2016-01-01

    Airframe noise corresponds to the acoustic radiation due to turbulent flow in the vicinity of airframe components such as high-lift devices and landing gears. Since 2010, the American Institute of Aeronautics and Astronautics has organized an ongoing series of workshops devoted to Benchmark Problems for Airframe Noise Computations (BANC). The BANC workshops are aimed at enabling a systematic progress in the understanding and high-fidelity predictions of airframe noise via collaborative investigations that integrate computational fluid dynamics, computational aeroacoustics, and in depth measurements targeting a selected set of canonical yet realistic configurations that advance the current state-of-the-art in multiple respects. Unique features of the BANC Workshops include: intrinsically multi-disciplinary focus involving both fluid dynamics and aeroacoustics, holistic rather than predictive emphasis, concurrent, long term evolution of experiments and simulations with a powerful interplay between the two, and strongly integrative nature by virtue of multi-team, multi-facility, multiple-entry measurements. This paper illustrates these features in the context of the BANC problem categories and outlines some of the challenges involved and how they were addressed. A brief summary of the BANC effort, including its technical objectives, strategy, and selective outcomes thus far is also included.

  3. Investigation of Volumetric Sources in Airframe Noise Simulations

    NASA Technical Reports Server (NTRS)

    Casper, Jay H.; Lockard, David P.; Khorrami, Mehdi R.; Streett, Craig L.

    2004-01-01

    Hybrid methods for the prediction of airframe noise involve a simulation of the near field flow that is used as input to an acoustic propagation formula. The acoustic formulations discussed herein are those based on the Ffowcs Williams and Hawkings equation. Some questions have arisen in the published literature in regard to an apparently significant dependence of radiated noise predictions on the location of the integration surface used in the solution of the Ffowcs Williams and Hawkings equation. These differences in radiated noise levels are most pronounced between solid-body surface integrals and off-body, permeable surface integrals. Such differences suggest that either a non-negligible volumetric source is contributing to the total radiation or the input flow simulation is suspect. The focus of the current work is the issue of internal consistency of the flow calculations that are currently used as input to airframe noise predictions. The case study for this research is a computer simulation for a three-element, high-lift wing profile during landing conditions. The noise radiated from this flow is predicted by a two-dimensional, frequency-domain formulation of the Ffowcs Williams and Hawkings equation. Radiated sound from volumetric sources is assessed by comparison of a permeable surface integration with the sum of a solid-body surface integral and a volume integral. The separate noise predictions are found in good agreement.

  4. Integrating CFD, CAA, and Experiments Towards Benchmark Datasets for Airframe Noise Problems

    NASA Technical Reports Server (NTRS)

    Choudhari, Meelan M.; Yamamoto, Kazuomi

    2012-01-01

    Airframe noise corresponds to the acoustic radiation due to turbulent flow in the vicinity of airframe components such as high-lift devices and landing gears. The combination of geometric complexity, high Reynolds number turbulence, multiple regions of separation, and a strong coupling with adjacent physical components makes the problem of airframe noise highly challenging. Since 2010, the American Institute of Aeronautics and Astronautics has organized an ongoing series of workshops devoted to Benchmark Problems for Airframe Noise Computations (BANC). The BANC workshops are aimed at enabling a systematic progress in the understanding and high-fidelity predictions of airframe noise via collaborative investigations that integrate state of the art computational fluid dynamics, computational aeroacoustics, and in depth, holistic, and multifacility measurements targeting a selected set of canonical yet realistic configurations. This paper provides a brief summary of the BANC effort, including its technical objectives, strategy, and selective outcomes thus far.

  5. Small Engine Technology (SET). Task 33: Airframe, Integration, and Community Noise Study

    NASA Technical Reports Server (NTRS)

    Lieber, Lys S.; Elkins, Daniel; Golub, Robert A. (Technical Monitor)

    2002-01-01

    Task Order 33 had four primary objectives as follows: (1) Identify and prioritize the airframe noise reduction technologies needed to accomplish the NASA Pillar goals for business and regional aircraft. (2) Develop a model to estimate the effect of jet shear layer refraction and attenuation of internally generated source noise of a turbofan engine on the aircraft system noise. (3) Determine the effect on community noise of source noise changes of a generic turbofan engine operating from sea level to 15,000 feet. (4) Support lateral attenuation experiments conducted by NASA Langley at Wallops Island, VA, by coordinating opportunities for Contractor Aircraft to participate as a noise source during the noise measurements. Noise data and noise prediction tools, including airframe noise codes, from the NASA Advanced Subsonic Technology (AST) program were applied to assess the current status of noise reduction technologies relative to the NASA pillar goals for regional and small business jet aircraft. In addition, the noise prediction tools were applied to evaluate the effectiveness of airframe-related noise reduction concepts developed in the AST program on reducing the aircraft system noise. The AST noise data and acoustic prediction tools used in this study were furnished by NASA.

  6. Airframe Noise Prediction of a Full Aircraft in Model and Full Scale Using a Lattice Boltzmann Approach

    NASA Technical Reports Server (NTRS)

    Fares, Ehab; Duda, Benjamin; Khorrami, Mehdi R.

    2016-01-01

    Unsteady flow computations are presented for a Gulfstream aircraft model in landing configuration, i.e., flap deflected 39deg and main landing gear deployed. The simulations employ the lattice Boltzmann solver PowerFLOW(Trademark) to simultaneously capture the flow physics and acoustics in the near field. Sound propagation to the far field is obtained using a Ffowcs Williams and Hawkings acoustic analogy approach. Two geometry representations of the same aircraft are analyzed: an 18% scale, high-fidelity, semi-span model at wind tunnel Reynolds number and a full-scale, full-span model at half-flight Reynolds number. Previously published and newly generated model-scale results are presented; all full-scale data are disclosed here for the first time. Reynolds number and geometrical fidelity effects are carefully examined to discern aerodynamic and aeroacoustic trends with a special focus on the scaling of surface pressure fluctuations and farfield noise. An additional study of the effects of geometrical detail on farfield noise is also documented. The present investigation reveals that, overall, the model-scale and full-scale aeroacoustic results compare rather well. Nevertheless, the study also highlights that finer geometrical details that are typically not captured at model scales can have a non-negligible contribution to the farfield noise signature.

  7. Numerical investigation of tandem-cylinder aerodynamic noise and its control with application to airframe noise

    NASA Astrophysics Data System (ADS)

    Eltaweel, Ahmed

    Prediction and reduction of airframe noise are critically important to the development of quieter civil transport aircraft. The key to noise reduction is a full understanding of the underlying noise source mechanisms. In this study, tandem cylinders in cross-flow as an idealization of a complex aircraft landing gear configuration are considered to investigate the noise generation and its reduction by flow control using single dielectric barrier discharge plasma actuators. The flow over tandem cylinders at ReD = 22, 000 with and without plasma actuation is computed using large-eddy simulation. The plasma effect is modeled as a body force obtained from a semi-empirical model. The flow statistics and surface pressure frequency spectra show excellent agreement with previous experimental measurements. For acoustic calculations, a boundary-element method is implemented to solve the convected Lighthill equation. The solution method is validated in a number of benchmark problems including flows over a cylinder, a rod-airfoil configuration, and a sphere. With validated flow field and acoustic solver, acoustic analysis is performed for the tandem-cylinder configuration to extend the experimental results and understand the mechanisms of noise generation and its control. Without flow control, the acoustic field is dominated by the interaction between the downstream cylinder and the upstream wake. Through suppression of vortex shedding from the upstream cylinder, the interaction noise is reduced drastically by the plasma flow control, and the vortex-shedding noise from the downstream cylinder becomes equally important. At a free-stream Mach number of 0.2, the peak sound pressure level is reduced by approximately 16 dB. This suggests the viability of plasma actuation for active control of airframe noise. The numerical investigation is extended to the noise from a realistic landing gear experimental model. Coarse-mesh computations are performed, and preliminary results are

  8. Airframe Noise from a Hybrid Wing Body Aircraft Configuration

    NASA Technical Reports Server (NTRS)

    Hutcheson, Florence V.; Spalt, Taylor B.; Brooks, Thomas F.; Plassman, Gerald E.

    2016-01-01

    A high fidelity aeroacoustic test was conducted in the NASA Langley 14- by 22-Foot Subsonic Tunnel to establish a detailed database of component noise for a 5.8% scale HWB aircraft configuration. The model has a modular design, which includes a drooped and a stowed wing leading edge, deflectable elevons, twin verticals, and a landing gear system with geometrically scaled wheel-wells. The model is mounted inverted in the test section and noise measurements are acquired at different streamwise stations from an overhead microphone phased array and from overhead and sideline microphones. Noise source distribution maps and component noise spectra are presented for airframe configurations representing two different approach flight conditions. Array measurements performed along the aircraft flyover line show the main landing gear to be the dominant contributor to the total airframe noise, followed by the nose gear, the inboard side-edges of the LE droop, the wing tip/LE droop outboard side-edges, and the side-edges of deployed elevons. Velocity dependence and flyover directivity are presented for the main noise components. Decorrelation effects from turbulence scattering on spectral levels measured with the microphone phased array are discussed. Finally, noise directivity maps obtained from the overhead and sideline microphone measurements for the landing gear system are provided for a broad range of observer locations.

  9. Application of Circulation Control Technology to Airframe Noise Reduction

    NASA Technical Reports Server (NTRS)

    Ahuja, K. K.; Sankar, L. N.; Englar, R. J.; Munro, Scott E.; Li, Yi; Gaeta, R. J.

    2003-01-01

    This report is a summary of the work performed by Georgia Tech Research Institute (GTRI) under NASA Langley Grant NAG-1-2146, which was awarded as a part of NASA's Breakthrough Innovative Technologies (BIT) initiative. This was a three-year program, with a one-year no-cost extension. Each year's study has been an integrated effort consisting of computational fluid dynamics, experimental aerodynamics, and detailed noise and flow measurements. Year I effort examined the feasibility of reducing airframe noise by replacing the conventional wing systems with a Circulation Control Wing (CCW), where steady blowing was used through the trailing edge of the wing over a Coanda surface. It was shown that the wing lift increases with CCW blowing and indeed for the same lift, a CCW wing was shown to produce less noise. Year 2 effort dealt with a similar study on the role of pulsed blowing on airframe noise. The main objective of this portion of the study was to assess whether pulse blowing from the trailing edge of a CCW resulted in more, less, or the same amount of radiated noise to the farfield. Results show that a reduction in farfield noise of up to 5 dB is measured when pulse flow is compared with steady flow for an equivalent lift configuration. This reduction is in the spectral region associated with the trailing edge jet noise. This result is due to the unique advantage that pulsed flow has over steady flow. For a range of frequencies, more lift is experienced with the same mass flow as the steady case. Thus, for an equivalent lift and slot height, the pulsed system can operate at lower jet velocities, and hence lower jet noise. The computational analysis showed that for a given time-averaged mass flow rate, pulsed jets give a higher value of C(sub l) and a higher L/D than equivalent steady jets. This benefit is attributable to higher instantaneous jet velocities, and higher instantaneous C(sub mu) values for the pulsed jet. Pulsed jet benefits increase at higher

  10. Preliminary measurements of aircraft airframe noise with the NASA CV-990 aircraft

    NASA Technical Reports Server (NTRS)

    White, K. C.; Lasagna, P. L.; Putnam, T. W.

    1976-01-01

    Flight tests were conducted in a CV-990 jet transport with engines at idle power to investigate aircraft airframe noise. Test results showed that airframe noise was measured for the aircraft in the landing configuration. The results agreed well with the expected variation with the fifth power of velocity. For the aircraft in the clean configuraton, it was concluded that airframe noise was measured only at higher airspeeds with engine idle noise present at lower speeds. The data show that landing gear and flaps make a significant contribution to airframe noise.

  11. Airframe Noise Results from the QTD II Flight Test Program

    NASA Technical Reports Server (NTRS)

    Elkoby, Ronen; Brusniak, Leon; Stoker, Robert W.; Khorrami, Mehdi R.; Abeysinghe, Amal; Moe, Jefferey W.

    2007-01-01

    With continued growth in air travel, sensitivity to community noise intensifies and materializes in the form of increased monitoring, regulations, and restrictions. Accordingly, realization of quieter aircraft is imperative, albeit only achievable with reduction of both engine and airframe components of total aircraft noise. Model-scale airframe noise testing has aided in this pursuit; however, the results are somewhat limited due to lack of fidelity of model hardware, particularly in simulating full-scale landing gear. Moreover, simulation of true in-flight conditions is non-trivial if not infeasible. This paper reports on an investigation of full-scale landing gear noise measured as part of the 2005 Quiet Technology Demonstrator 2 (QTD2) flight test program. Conventional Boeing 777-300ER main landing gear were tested, along with two noise reduction concepts, namely a toboggan fairing and gear alignment with the local flow, both of which were down-selected from various other noise reduction devices evaluated in model-scale testing at Virginia Tech. The full-scale toboggan fairings were designed by Goodrich Aerostructures as add-on devices allowing for complete retraction of the main gear. The baseline-conventional gear, faired gear, and aligned gear were all evaluated with the high-lift system in the retracted position and deployed at various flap settings, all at engine idle power setting. Measurements were taken with flyover community noise microphones and a large aperture acoustic phased array, yielding far-field spectra, and localized sources (beamform maps). The results were utilized to evaluate qualitatively and quantitatively the merit of each noise reduction concept. Complete similarity between model-scale and full-scale noise reduction levels was not found and requires further investigation. Far-field spectra exhibited no noise reduction for both concepts across all angles and frequencies. Phased array beamform maps show inconclusive evidence of noise

  12. Tip Fence for Reduction of Lift-Generated Airframe Noise

    NASA Technical Reports Server (NTRS)

    Ross, James C. (Inventor); Storms, Bruce L. (Inventor)

    1998-01-01

    The present invention is directed toward a unique lift-generated noise reduction apparatus. This apparatus includes a plurality of tip fences that are secured to the trailing and leading assemblies of the high-lift system, as close as possible to the discontinuities where the vortices are most likely to form. In one embodiment, these tip fences are secured to some or all of the outboard and inboard tips of the wing slats and flaps. The tip fence includes a generally flat, or an aerodynamically shaped plate or device that could be formed of almost any rigid material, such as metal, wood, plastic, fiber glass, aluminum, etc. In a preferred embodiment, the tip fences extend below and perpendicularly to flaps and the slats to which they are attached, such that these tip fences are aligned with the nominal free stream velocity of the aircraft. In addition to reducing airframe noise, the tip fence tends to decrease drag and to increase lift, thus improving the overall aerodynamic performance of the aircraft. Another advantage presented by the tip fence lies in the simplicity of its design, its elegance, and its ready ability to fit on the wing components, such as the flaps and the slats. Furthermore, it does not require non-standard materials or fabrication techniques, and it can be readily, easily and inexpensively retrofited on most of the existing aircraft, with minimal design changes.

  13. In Search of the Physics: NASA's Approach to Airframe Noise

    NASA Technical Reports Server (NTRS)

    Macaraeg, Michele G.; Lockard, David P.; Streett, Craig L.

    1999-01-01

    An extensive numerical and experimental study of airframe noise mechanisms associated with a subsonic high-lift system has been performed at NASA Langley Research Center (LaRC). Investigations involving both steady and unsteady computations and experiments on small-scale models with part-span flaps and full-span flaps are presented. Both surface (steady and unsteady pressure measurements, hot films, oil flows, pressure sensitive paint) and off-surface (5 holeprobe, particle-imaged velocimetry, laser velocimetry, laser light sheet measurements) were taken in the LaRC Quiet Flow Facility (QFF) and several hard-wall tunnels. Experiments in the Low Turbulence Pressure Tunnel (LTPT) included Reynolds number variations up to flight conditions. Successful microphone array measurements were also taken providing both acoustic source maps on the model, and quantitative spectra. Critical directivity measurements were obtained in the QFF. NASA Langley unstructured and structured Reynolds-Averaged Navier-Stokes codes modeled the steady aspects of the flows. Excellent comparisons with surface and off-surface experimental data were obtained. Subsequently, these meanflow calculations were utilized in both linear stability and direct numerical simulations of the flow fields to calculate unsteady surface pressures and farfield acoustic spectra. Accurate calculations were critical in obtaining not only noise source characteristics, but shear layer correction data as well. Techniques utilized in these investigations as well as brief overviews of the results are given.

  14. Hybrid Wing Body Aircraft System Noise Assessment with Propulsion Airframe Aeroacoustic Experiments

    NASA Technical Reports Server (NTRS)

    Thomas, Russell H.; Burley, Casey L.; Olson, Erik D.

    2010-01-01

    A system noise assessment of a hybrid wing body configuration was performed using NASA s best available aircraft models, engine model, and system noise assessment method. A propulsion airframe aeroacoustic effects experimental database for key noise sources and interaction effects was used to provide data directly in the noise assessment where prediction methods are inadequate. NASA engine and aircraft system models were created to define the hybrid wing body aircraft concept as a twin engine aircraft with a 7500 nautical mile mission. The engines were modeled as existing technology high bypass ratio turbofans. The baseline hybrid wing body aircraft was assessed at 22 dB cumulative below the FAA Stage 4 certification level. To determine the potential for noise reduction with relatively near term technologies, seven other configurations were assessed beginning with moving the engines two fan nozzle diameters upstream of the trailing edge and then adding technologies for reduction of the highest noise sources. Aft radiated noise was expected to be the most challenging to reduce and, therefore, the experimental database focused on jet nozzle and pylon configurations that could reduce jet noise through a combination of source reduction and shielding effectiveness. The best configuration for reduction of jet noise used state-of-the-art technology chevrons with a pylon above the engine in the crown position. This configuration resulted in jet source noise reduction, favorable azimuthal directivity, and noise source relocation upstream where it is more effectively shielded by the limited airframe surface, and additional fan noise attenuation from acoustic liner on the crown pylon internal surfaces. Vertical and elevon surfaces were also assessed to add shielding area. The elevon deflection above the trailing edge showed some small additional noise reduction whereas vertical surfaces resulted in a slight noise increase. With the effects of the configurations from the

  15. Aircraft noise prediction program theoretical manual, part 2

    NASA Astrophysics Data System (ADS)

    Zorumski, W. E.

    1982-02-01

    Detailed prediction methods for specific aircraft noise sources are given. These sources are airframe noise, combustion noise, fan noise, single and dual stream jet noise, and turbine noise. Modifications to the NASA methods which comply with the International Civil Aviation Organization standard method for aircraft noise prediction are given.

  16. A Comparison of Ffowcs Williams-Hawkings Solvers for Airframe Noise Applications

    NASA Technical Reports Server (NTRS)

    Lockard, David P.

    2002-01-01

    This paper presents a comparison between two implementations of the Ffowcs Williams and Hawkings equation for airframe noise applications. Airframe systems are generally moving at constant speed and not rotating, so these conditions are used in the current investigation. Efficient and easily implemented forms of the equations applicable to subsonic, rectilinear motion of all acoustic sources are used. The assumptions allow the derivation of a simple form of the equations in the frequency-domain, and the time-domain method uses the restrictions on the motion to reduce the work required to find the emission time. The comparison between the frequency domain method and the retarded time formulation reveals some of the advantages of the different approaches. Both methods are still capable of predicting the far-field noise from nonlinear near-field flow quantities. Because of the large input data sets and potentially large numbers of observer positions of interest in three-dimensional problems, both codes utilize the message passing interface to divide the problem among different processors. Example problems are used to demonstrate the usefulness and efficiency of the two schemes.

  17. Preliminary Analysis of Acoustic Measurements from the NASA-Gulfstream Airframe Noise Flight Test

    NASA Technical Reports Server (NTRS)

    Khorrami, Mehdi R.; Lockhard, David D.; Humphreys, Willliam M.; Choudhari, Meelan M.; Van De Ven, Thomas

    2008-01-01

    The NASA-Gulfstream joint Airframe Noise Flight Test program was conducted at the NASA Wallops Flight Facility during October, 2006. The primary objective of the AFN flight test was to acquire baseline airframe noise data on a regional jet class of transport in order to determine noise source strengths and distributions for model validation. To accomplish this task, two measuring systems were used: a ground-based microphone array and individual microphones. Acoustic data for a Gulfstream G550 aircraft were acquired over the course of ten days. Over twenty-four test conditions were flown. The test matrix was designed to provide an acoustic characterization of both the full aircraft and individual airframe components and included cruise to landing configurations. Noise sources were isolated by selectively deploying individual components (flaps, main landing gear, nose gear, spoilers, etc.) and altering the airspeed, glide path, and engine settings. The AFN flight test program confirmed that the airframe is a major contributor to the noise from regional jets during landing operations. Sound pressure levels from the individual microphones on the ground revealed the flap system to be the dominant airframe noise source for the G550 aircraft. The corresponding array beamform maps showed that most of the radiated sound from the flaps originates from the side edges. Using velocity to the sixth power and Strouhal scaling of the sound pressure spectra obtained at different speeds failed to collapse the data into a single spectrum. The best data collapse was obtained when the frequencies were left unscaled.

  18. Computational Evaluation of Airframe Noise Reduction Concepts at Full Scale

    NASA Technical Reports Server (NTRS)

    Khorrami, Mehdi R.; Duda, Benjamin; Hazir, Andreas; Fares, Ehab

    2016-01-01

    High-fidelity simulations focused on full-scale evaluation of new technologies for mitigating flap and landing gear noise are presented. These noise reduction concepts were selected because of their superior acoustic performance, as demonstrated during NASA wind tunnel tests of an 18%-scale, semi-span model of a Gulfstream aircraft. The full-scale, full-aircraft, time-accurate simulations were performed with the lattice Boltzmann PowerFLOW(Registered Trademark) solver for free air at a Mach number of 0.2. Three aircraft configurations (flaps deflected at 39? without and with main gear deployed, and 0? flaps with main gear extended) were used to determine the aero-acoustic performance of the concepts on component-level (individually) and system-level (concurrent applica-tion) bases. Farfield noise spectra were obtained using a Ffowcs-Williams and Hawkings acoustic analogy approach. Comparison of the predicted spectra without (baseline) and with the noise treatments applied showed that noise reduction benefits between 2-3 dB for the flap and 1.3-1.7 dB for the main landing gear are obtained. It was also found that the full extent of the benefits is being masked by the noise generated from the flap brackets and main gear cavities, which act as prominent secondary sources.

  19. Suppressor nozzle and airframe noise measurements during flyover of a modified F106B aircraft with underwing nacelles

    NASA Technical Reports Server (NTRS)

    Burley, R. R.

    1974-01-01

    The effect of flight velocity on the jet noise and thrust of a 104-tube suppressor nozzle was investigated using an F-106B delta wing aircraft modified to carry two underwing nacelles each containing a turbojet engine. The nozzle was mounted behind one of the nacelles. Flight velocity had a large adverse effect on thrust and a small adverse effect on suppression when correlated with relative jet velocity. The clean airframe noise of the aircraft was measured at Mach 0.4 and was compared with that predicted from an empirical expression. The 83 db measured value was considerably below the predicted value.

  20. Flap Side Edge Liners for Airframe Noise Reduction

    NASA Technical Reports Server (NTRS)

    Jones, Michael G. (Inventor); Khorrami, Mehdi R. (Inventor); Choudhari, Meelan M. (Inventor); Howerton, Brian M. (Inventor)

    2014-01-01

    One or more acoustic liners comprising internal chambers or passageways that absorb energy from a noise source on the aircraft are disclosed. The acoustic liners may be positioned at the ends of flaps of an aircraft wing to provide broadband noise absorption and/or dampen the noise producing unsteady flow features, and to reduce the amount of noise generated due to unsteady flow at the inboard and/or outboard end edges of a flap.

  1. Research needs in aircraft noise prediction

    NASA Technical Reports Server (NTRS)

    Raney, J. P.

    1975-01-01

    Progress needed in understanding the mechanisms of aircraft noise generation and propagation is outlined using the focus provided by the need to predict accurately the noise produced and received at the ground by an aircraft operating in the vicinity of an airport. The components of internal engine noise generation, jet exhaust, airframe noise and shielding and configuration effects, and the roles of atmospheric propagation and ground noise attenuation are presented and related to the prediction problem. The role of NASA in providing the focus and direction for needed advances is discussed, and possible contributions of the academic community in helping to fulfill the needs for accurate aircraft noise prediction methods are suggested.

  2. Database of Inlet and Exhaust Noise Shielding for Wedge-Shaped Airframe

    NASA Technical Reports Server (NTRS)

    Gerhold, Carl H.; Clark, Lorenzo R.

    2001-01-01

    An experiment to measure the noise shielding of the blended wing body design concept was developed using a simplified wedge-shaped airframe. The experimental study was conducted in the Langley Anechoic Noise Research Facility. A wideband, omnidirective sound source in a simulated engine nacelle was held at locations representative of a range of engine locations above the wing. The sound field around the model was measured with the airframe and source in place and with source alone, using an-array of microphones on a rotating hoop that is also translated along an axis parallel to the airframe axis. The insertion loss was determined from the difference between the two resulting contours. Although no attempt was made to simulate the noise characteristics of a particular engine, the broadband noise source radiated sound over a range of scaled frequencies encompassing 1 and 2 times the blade passage frequency representative of a large, high-bypass-ratio turbofan engine. The measured data show that significant shielding of the inlet-radiated noise is obtained in the area beneath and upstream of the model. The data show the sensitivity of insertion loss to engine location.

  3. Low-frequency noise reduction of lightweight airframe structures

    NASA Technical Reports Server (NTRS)

    Getline, G. L.

    1976-01-01

    The results of an experimental study to determine the noise attenuation characteristics of aircraft type fuselage structural panels were presented. Of particular interest was noise attenuation at low frequencies, below the fundamental resonances of the panels. All panels were flightweight structures for transport type aircraft in the 34,050 to 45,400 kg (75,000 to 100,000 pounds) gross weight range. Test data include the results of vibration and acoustic transmission loss tests on seven types of isotropic and orthotropically stiffened, flat and curved panels. The results show that stiffness controlled acoustically integrated structures can provide very high noise reductions at low frequencies without significantly affecting their high frequency noise reduction capabilities.

  4. Landing Gear Door Liners for Airframe Noise Reduction

    NASA Technical Reports Server (NTRS)

    Jones, Michael G. (Inventor); Howerton, Brian M. (Inventor); Van De Ven, Thomas (Inventor)

    2014-01-01

    A landing gear door for retractable landing gear of aircraft includes an acoustic liner. The acoustic liner includes one or more internal cavities or chambers having one or more openings that inhibit the generation of sound at the surface and/or absorb sound generated during operation of the aircraft. The landing gear door may include a plurality of internal chambers having different geometries to thereby absorb broadband noise.

  5. Application of MEMS Microphone Array Technology to Airframe Noise Measurements

    NASA Technical Reports Server (NTRS)

    Humphreys, William M., Jr.; Shams, Qamar A.; Graves, Sharon S.; Sealey, Bradley S.; Bartram, Scott M.; Comeaux, Toby

    2005-01-01

    Current generation microphone directional array instrumentation is capable of extracting accurate noise source location and directivity data on a variety of aircraft components, resulting in significant gains in test productivity. However, with this gain in productivity has come the desire to install larger and more complex arrays in a variety of ground test facilities, creating new challenges for the designers of array systems. To overcome these challenges, a research study was initiated to identify and develop hardware and fabrication technologies which could be used to construct an array system exhibiting acceptable measurement performance but at much lower cost and with much simpler installation requirements. This paper describes an effort to fabricate a 128-sensor array using commercially available Micro-Electro-Mechanical System (MEMS) microphones. The MEMS array was used to acquire noise data for an isolated 26%-scale high-fidelity Boeing 777 landing gear in the Virginia Polytechnic Institute and State University Stability Tunnel across a range of Mach numbers. The overall performance of the array was excellent, and major noise sources were successfully identified from the measurements.

  6. Unsteady Flowfield Around Tandem Cylinders as Prototype for Component Interaction in Airframe Noise

    NASA Technical Reports Server (NTRS)

    Khorrami, Meldi R.; Choudhari, Meelan M.; Jenkins, Luther N.; McGinley, Catherine B.

    2005-01-01

    Synergistic application of experiments and numerical simulations is crucial to understanding the underlying physics of airframe noise sources. The current effort is aimed at characterizing the details of the flow interaction between two cylinders in a tandem configuration. This setup is viewed to be representative of several component-level flow interactions that occur when air flows over the main landing gear of large civil transports. Interactions of this type are likely to have a significant impact on the noise radiation associated with the aircraft undercarriage. The paper is focused on two-dimensional, time-accurate flow simulations for the tandem cylinder configuration. Results of the unsteady Reynolds Averaged Navier-Stokes (URANS) computations with a two-equation turbulence model, at a Reynolds number of 0.166 million and a Mach number of 0.166, are presented. The experimental measurements of the same flow field are discussed in a separate paper by Jenkins, Khorrami, Choudhari, and McGinley (2005). Two distinct flow regimes of interest, associated with short and intermediate separation distances between the two cylinders, are considered. Emphasis is placed on understanding both time averaged and unsteady flow features between the two cylinders and in the wake of the rear cylinder. Predicted mean flow quantities and vortex shedding frequencies show reasonable agreement with the measured data for both cylinder spacings. Computations for short separation distance indicate decay of flow unsteadiness with time, which is not unphysical; however, the predicted sensitivity of mean lift coefficient to small angles of attack explains the asymmetric flowfield observed during the experiments.

  7. In Search of the Physics: The Interplay of Experiment and Computation in Airframe Noise Research: Flap-Edge Noise

    NASA Technical Reports Server (NTRS)

    Streett, C. L.; Lockard, D. P.; Singer, B. A.; Khorrami, M. R.; Choudhari, M. M.

    2003-01-01

    The LaRC investigative process for airframe noise has proven to be a useful guide for elucidation of the physics of flow-induced noise generation over the last five years. This process, relying on a close interplay between experiment and computation, is described and demonstrated here on the archetypal problem of flap-edge noise. Some detailed results from both experiment and computation are shown to illustrate the process, and a description of the multi-source physics seen in this problem is conjectured.

  8. Characterization of Flap Edge Noise Radiation from a High-Fidelity Airframe Model

    NASA Technical Reports Server (NTRS)

    Humphreys, William M., Jr.; Khorrami, Mehdi R.; Lockhard, David P.; Neuhart, Dan H.; Bahr, Christopher J.

    2015-01-01

    The results of an experimental study of the noise generated by a baseline high-fidelity airframe model are presented. The test campaign was conducted in the open-jet test section of the NASA Langley 14- by 22-foot Subsonic Tunnel on an 18%-scale, semi-span Gulfstream airframe model incorporating a trailing edge flap and main landing gear. Unsteady surface pressure measurements were obtained from a series of sensors positioned along the two flap edges, and far field acoustic measurements were obtained using a 97-microphone phased array that viewed the pressure side of the airframe. The DAMAS array deconvolution method was employed to determine the locations and strengths of relevant noise sources in the vicinity of the flap edges and the landing gear. A Coherent Output Power (COP) spectral method was used to couple the unsteady surface pressures measured along the flap edges with the phased array output. The results indicate that outboard flap edge noise is dominated by the flap bulb seal cavity with very strong COP coherence over an approximate model-scale frequency range of 1 to 5 kHz observed between the array output and those unsteady pressure sensors nearest the aft end of the cavity. An examination of experimental COP spectra for the inboard flap proved inconclusive, most likely due to a combination of coherence loss caused by decorrelation of acoustic waves propagating through the thick wind tunnel shear layer and contamination of the spectra by tunnel background noise at lower frequencies. Directivity measurements obtained from integration of DAMAS pressure-squared values over defined geometric zones around the model show that the baseline flap and landing gear are only moderately directional as a function of polar emission angle.

  9. Development of a SMA-Based, Slat-Gap Filler for Airframe Noise Reduction

    NASA Technical Reports Server (NTRS)

    Turner, Travis L.; Long, David L.

    2015-01-01

    Noise produced by unsteady flow around aircraft structures, termed airframe noise, is an important source of aircraft noise during the approach and landing phases of flight. Conventional leading-edge-slat devices for high lift on typical transport aircraft are a prominent source of airframe noise. Many concepts for slat noise reduction have been investigated. Slat-cove fillers have emerged as an attractive solution, but they maintain the gap flow, leaving some noise production mechanisms unabated, and thus represent a nonoptimal solution. Drooped-leading-edge (DLE) concepts have been proposed as "optimal" because the gap flow is eliminated. The deployed leading edge device is not distinct and separate from the main wing in DLE concepts and the high-lift performance suffers at high angles of attack (alpha) as a consequence. Elusive high-alpha performance and excessive weight penalty have stymied DLE development. The fact that high-lift performance of DLE systems is only affected at high alpha suggests another concept that simultaneously achieves the high-lift of the baseline airfoil and the noise reduction of DLE concepts. The concept involves utilizing a conventional leading-edge slat device and a deformable structure that is deployed from the leading edge of the main wing and closes the gap between the slat and main wing, termed a slat-gap filler (SGF). The deployable structure consists of a portion of the skin of the main wing and it is driven in conjunction with the slat during deployment and retraction. Benchtop models have been developed to assess the feasibility and to study important parameters. Computational models have assisted in the bench-top model design and provided valuable insight in the parameter space as well as the feasibility.

  10. Computer program to predict aircraft noise levels

    NASA Technical Reports Server (NTRS)

    Clark, B. J.

    1981-01-01

    Methods developed at the NASA Lewis Research Center for predicting the noise contributions from various aircraft noise sources were programmed to predict aircraft noise levels either in flight or in ground tests. The noise sources include fan inlet and exhaust, jet, flap (for powered lift), core (combustor), turbine, and airframe. Noise propagation corrections are available for atmospheric attenuation, ground reflections, extra ground attenuation, and shielding. Outputs can include spectra, overall sound pressure level, perceived noise level, tone-weighted perceived noise level, and effective perceived noise level at locations specified by the user. Footprint contour coordinates and approximate footprint areas can also be calculated. Inputs and outputs can be in either System International or U.S. customary units. The subroutines for each noise source and propagation correction are described. A complete listing is given.

  11. Assessment of NASA's Aircraft Noise Prediction Capability

    NASA Technical Reports Server (NTRS)

    Dahl, Milo D. (Editor)

    2012-01-01

    A goal of NASA s Fundamental Aeronautics Program is the improvement of aircraft noise prediction. This document provides an assessment, conducted from 2006 to 2009, on the current state of the art for aircraft noise prediction by carefully analyzing the results from prediction tools and from the experimental databases to determine errors and uncertainties and compare results to validate the predictions. The error analysis is included for both the predictions and the experimental data and helps identify where improvements are required. This study is restricted to prediction methods and databases developed or sponsored by NASA, although in many cases they represent the current state of the art for industry. The present document begins with an introduction giving a general background for and a discussion on the process of this assessment followed by eight chapters covering topics at both the system and the component levels. The topic areas, each with multiple contributors, are aircraft system noise, engine system noise, airframe noise, fan noise, liner physics, duct acoustics, jet noise, and propulsion airframe aeroacoustics.

  12. Flight Test Results for Uniquely Tailored Propulsion-Airframe Aeroacoustic Chevrons: Shockcell Noise

    NASA Technical Reports Server (NTRS)

    Mengle, Vinod G.; Ganz, Ulrich W.; Nesbitt, Eric; Bultemeier, Eric J.; Thomas, Russell H.; Nesbitt, Eric

    2006-01-01

    Azimuthally varying chevrons (AVC) which have been uniquely tailored to account for the asymmetric propulsion-airframe aeroacoustic interactions have recently shown significant reductions in jet-related community noise at low-speed take-off conditions in scale model tests of coaxial nozzles with high bypass ratio. There were indications that such AVCs may also provide shockcell noise reductions at high cruise speeds. This paper describes the flight test results when one such AVC concept, namely, the T-fan chevrons with enhanced mixing near the pylon, was tested at full-scale on a modern large twin-jet aircraft (777-300ER) with focus on shockcell noise at mid-cruise conditions. Shockcell noise is part of the interior cabin noise at cruise conditions and its reduction is useful from the viewpoint of passenger comfort. Noise reduction at the source, in the exhaust jet, especially, at low frequencies, is beneficial from the perspective of reduced fuselage sidewall acoustic lining. Results are shown in terms of unsteady pressure spectra both on the exterior surface of the fuselage at several axial stations and also microphone arrays placed inside the fuselage aft of the engine. The benefits of T-fan chevrons, with and without conventional chevrons on the core nozzle, are shown for several engine operating conditions at cruise involving supersonic fan stream and subsonic or supersonic core stream. The T-fan AVC alone provides up to 5 dB low-frequency noise reduction on the fuselage exterior skin and up to 2 dB reduction inside the cabin. Addition of core chevrons appears to increase the higher frequency noise. This flight test result with the previous model test observation that the T-fan AVCs have hardly any cruise thrust coefficient loss (< 0.05%) make them viable candidates for reducing interior cabin noise in high bypass ratio engines.

  13. Flight Test Results for Uniquely Tailored Propulsion-Airframe Aeroacoustic Chevrons: Community Noise

    NASA Technical Reports Server (NTRS)

    Nesbitt, Eric; Mengle, Vinod; Czech, Michael; Callendar, Bryan; Thomas, Russ

    2006-01-01

    The flow/acoustic environment around the jet exhaust of an engine when installed on an airplane, say, under the wing, is highly asymmetric due to the pylon, the wing and the high-lift devices. Recent scale model tests have shown that such Propulsion Airframe Aeroacoustic (PAA) interactions and the jet mixing noise can be reduced more than with conventional azimuthally uniform chevrons by uniquely tailoring the chevrons to produce enhanced mixing near the pylon. This paper describes the community noise results from a flight test on a large twin-engine airplane using this concept of azimuthally varying chevrons for engines installed under the wing. Results for two different nozzle configurations are described: azimuthally varying "PAA T-fan" chevrons on the fan nozzle with a baseline no-chevron core nozzle and a second with PAA T-fan chevrons with conventional azimuthally uniform chevrons on the core nozzle. We analyze these test results in comparison to the baseline no-chevron nozzle on both spectral and integrated power level bases. The study focuses on the peak jet noise reduction and the effects at high frequencies for typical take-off power settings. The noise reduction and the absolute noise levels are then compared to model scale results. The flight test results verify that the PAA T-fan nozzles in combination with standard core chevron nozzles can, indeed, give a reasonable amount of noise reduction at low frequencies without high-frequency lift during take-off conditions and hardly any impact on the cruise thrust coefficient.

  14. Effect of Directional Array Size on the Measurement of Airframe Noise Components

    NASA Technical Reports Server (NTRS)

    Brooks, Thomas F.; Humphreys, William M., Jr.

    1999-01-01

    A study was conducted to examine the effects of overall size of directional (or phased) arrays on the measurement of aeroacoustic components. An airframe model was mounted in the potential core of an open-jet windtunnel, with the directional arrays located outside the flow in an anechoic environment. Two array systems were used; one with a solid measurement angle that encompasses 31.6 deg.of source directivity and a smaller one that encompasses 7.2 deg. The arrays, and sub-arrays of various sizes, measured noise from a calibrator source and flap edge model setups. In these cases, noise was emitted from relatively small, but finite size source regions, with intense levels compared to other sources. Although the larger arrays revealed much more source region detail, the measured source levels were substantially reduced due to finer resolution compared to that of the smaller arrays. To better understand the measurements quantitatively, an analytical model was used to define the basic relationships between array to source region sizes and measured output level. Also, the effect of noise scattering by shear layer turbulence was examined using the present data and those of previous studies. Taken together, the two effects were sufficient to explain spectral level differences between arrays of different sizes. An important result of this study is that total (integrated) noise source levels are retrievable and the levels are independent of the array size as long as certain experimental and processing criteria are met. The criteria for both open and closed tunnels are discussed. The success of special purpose diagonal-removal processing in obtaining integrated results is apparently dependent in part on source distribution. Also discussed is the fact that extended sources are subject to substantial measurement error, especially for large arrays.

  15. Toward Establishing a Realistic Benchmark for Airframe Noise Research: Issues and Challenges

    NASA Technical Reports Server (NTRS)

    Khorrami, Mehdi R.

    2010-01-01

    The availability of realistic benchmark configurations is essential to enable the validation of current Computational Aeroacoustic (CAA) methodologies and to further the development of new ideas and concepts that will foster the technologies of the next generation of CAA tools. The selection of a real-world configuration, the subsequent design and fabrication of an appropriate model for testing, and the acquisition of the necessarily comprehensive aeroacoustic data base are critical steps that demand great care and attention. In this paper, a brief account of the nose landing-gear configuration, being proposed jointly by NASA and the Gulfstream Aerospace Company as an airframe noise benchmark, is provided. The underlying thought processes and the resulting building block steps that were taken during the development of this benchmark case are given. Resolution of critical, yet conflicting issues is discussed - the desire to maintain geometric fidelity versus model modifications required to accommodate instrumentation; balancing model scale size versus Reynolds number effects; and time, cost, and facility availability versus important parameters like surface finish and installation effects. The decisions taken during the experimental phase of a study can significantly affect the ability of a CAA calculation to reproduce the prevalent flow conditions and associated measurements. For the nose landing gear, the most critical of such issues are highlighted and the compromises made to resolve them are discussed. The results of these compromises will be summarized by examining the positive attributes and shortcomings of this particular benchmark case.

  16. Modeling and Prediction of Krueger Device Noise

    NASA Technical Reports Server (NTRS)

    Guo, Yueping; Burley, Casey L.; Thomas, Russell H.

    2016-01-01

    This paper presents the development of a noise prediction model for aircraft Krueger flap devices that are considered as alternatives to leading edge slotted slats. The prediction model decomposes the total Krueger noise into four components, generated by the unsteady flows, respectively, in the cove under the pressure side surface of the Krueger, in the gap between the Krueger trailing edge and the main wing, around the brackets supporting the Krueger device, and around the cavity on the lower side of the main wing. For each noise component, the modeling follows a physics-based approach that aims at capturing the dominant noise-generating features in the flow and developing correlations between the noise and the flow parameters that control the noise generation processes. The far field noise is modeled using each of the four noise component's respective spectral functions, far field directivities, Mach number dependencies, component amplitudes, and other parametric trends. Preliminary validations are carried out by using small scale experimental data, and two applications are discussed; one for conventional aircraft and the other for advanced configurations. The former focuses on the parametric trends of Krueger noise on design parameters, while the latter reveals its importance in relation to other airframe noise components.

  17. Initial noise predictions for rudimentary landing gear

    NASA Astrophysics Data System (ADS)

    Spalart, Philippe R.; Shur, Mikhail L.; Strelets, Mikhail Kh.; Travin, Andrey K.

    2011-08-01

    A four-wheel "rudimentary" landing gear (RLG) truck was designed for public-domain research, with a level of complexity which is manageable in current numerical simulations, and a weak Reynolds-number sensitivity. Experimental measurements of wall-pressure fluctuations are allowing a meaningful test of unsteady simulations with emphasis on noise generation. We present three Detached-Eddy Simulations (DES) using up to 18 million points in the high-order NTS code. The first is incompressible with the model placed in the wind tunnel, as requested for the 2010 workshop on Benchmark problems for Airframe Noise Computations (BANC-I), intended for force and surface-pressure studies. The second and third are at Mach 0.115 and Mach 0.23, with only one wall, a "ceiling" analogous to a wing (but infinite and inviscid), and are used to exercise far-field noise prediction by coupling the Detached-Eddy Simulations and a Ffowcs-Williams/Hawkings calculation. The results include wall-pressure, and far-field-noise intensities and spectra. The wall pressure signals in the three simulations are very similar and, in a comparison published separately, agree well with experiment and other simulations. In the absence of experimental noise data, the attention is focused on internal quality checks, by varying the permeable Ffowcs-Williams/Hawkings calculation surface and then by using only the solid surface. An unexpected finding at these Mach numbers is an apparent strong role for quadrupoles, revealed by a typical deficit of 3 dB in the solid-surface results, relative to the permeable-surface results. The solid-surface approach has variants, related to the presence of the ceiling (a plane of symmetry), which can increase this error further; there is little consensus on the exact configuration of the solid surfaces in the Ffowcs-Williams/Hawkings calculation procedure. Tentative theoretical arguments suggest that a balance somewhat in favor of quadrupoles over dipoles is plausible at Mach

  18. Overview of Aircraft Noise Prediction Tools Assessment

    NASA Technical Reports Server (NTRS)

    Dahl, Milo D.

    2007-01-01

    The acoustic assessment task for both the Subsonic Fixed Wing and the Supersonic projects under NASA s Fundamental Aeronautics Program was designed to assess the current state-of-the-art in noise prediction capability and to establish baselines for gauging future progress. The documentation of our current capabilities included quantifying the differences between predictions of noise from computer codes and measurements of noise from experimental tests. Quantifying the accuracy of both the computed and experimental results further enhanced the credibility of the assessment. This presentation gives sample results from codes representative of NASA s capabilities in aircraft noise prediction at the system level and at the component level. These include semi-empirical, statistical, analytical, and numerical codes. An example of system level results is shown for an aircraft. Component level results are shown for airframe flaps and landing gear, for jet noise from a variety of nozzles, and for broadband fan noise. Additional results are shown for modeling of the acoustic behavior of duct acoustic lining and the attenuation of sound in lined ducts with flow.

  19. Evaluation of Airframe Noise Reduction Concepts via Simulations Using a Lattice Boltzmann Approach

    NASA Technical Reports Server (NTRS)

    Fares, Ehab; Casalino, Damiano; Khorrami, Mehdi R.

    2015-01-01

    Unsteady computations are presented for a high-fidelity, 18% scale, semi-span Gulfstream aircraft model in landing configuration, i.e. flap deflected at 39 degree and main landing gear deployed. The simulations employ the lattice Boltzmann solver PowerFLOW® to simultaneously capture the flow physics and acoustics in the near field. Sound propagation to the far field is obtained using a Ffowcs Williams and Hawkings acoustic analogy approach. In addition to the baseline geometry, which was presented previously, various noise reduction concepts for the flap and main landing gear are simulated. In particular, care is taken to fully resolve the complex geometrical details associated with these concepts in order to capture the resulting intricate local flow field thus enabling accurate prediction of their acoustic behavior. To determine aeroacoustic performance, the farfield noise predicted with the concepts applied is compared to high-fidelity simulations of the untreated baseline configurations. To assess the accuracy of the computed results, the aerodynamic and aeroacoustic impact of the noise reduction concepts is evaluated numerically and compared to experimental results for the same model. The trends and effectiveness of the simulated noise reduction concepts compare well with measured values and demonstrate that the computational approach is capable of capturing the primary effects of the acoustic treatment on a full aircraft model.

  20. Toward Improved CFD Predictions of Slender Airframe Aerodynamics Using the F-16XL Aircraft (CAWAPI-2)

    NASA Technical Reports Server (NTRS)

    Luckring, James M.; Rizzi, Arthur; Davis, M. Bruce

    2014-01-01

    A coordinated project has been underway to improve CFD predictions of slender airframe aerodynamics. The work is focused on two flow conditions and leverages a unique flight data set obtained with an F-16XL aircraft. These conditions, a low-speed high angleof- attack case and a transonic low angle-of-attack case, were selected from a prior prediction campaign wherein the CFD failed to provide acceptable results. In this paper the background, objectives and approach to the current project are presented. The work embodies predictions from multiple numerical formulations that are contributed from multiple organizations, and the context of this campaign to other multi-code, multiorganizational efforts is included. The relevance of this body of work toward future supersonic commercial transport concepts is also briefly addressed.

  1. The Prediction of Noise Due to Jet Turbulence Convecting Past Flight Vehicle Trailing Edges

    NASA Technical Reports Server (NTRS)

    Miller, Steven A. E.

    2014-01-01

    High intensity acoustic radiation occurs when turbulence convects past airframe trailing edges. A mathematical model is developed to predict this acoustic radiation. The model is dependent on the local flow and turbulent statistics above the trailing edge of the flight vehicle airframe. These quantities are dependent on the jet and flight vehicle Mach numbers and jet temperature. A term in the model approximates the turbulent statistics of single-stream heated jet flows and is developed based upon measurement. The developed model is valid for a wide range of jet Mach numbers, jet temperature ratios, and flight vehicle Mach numbers. The model predicts traditional trailing edge noise if the jet is not interacting with the airframe. Predictions of mean-flow quantities and the cross-spectrum of static pressure near the airframe trailing edge are compared with measurement. Finally, predictions of acoustic intensity are compared with measurement and the model is shown to accurately capture the phenomenon.

  2. Summary of the Tandem Cylinder Solutions from the Benchmark Problems for Airframe Noise Computations-I Workshop

    NASA Technical Reports Server (NTRS)

    Lockard, David P.

    2011-01-01

    Fifteen submissions in the tandem cylinders category of the First Workshop on Benchmark problems for Airframe Noise Computations are summarized. Although the geometry is relatively simple, the problem involves complex physics. Researchers employed various block-structured, overset, unstructured and embedded Cartesian grid techniques and considerable computational resources to simulate the flow. The solutions are compared against each other and experimental data from 2 facilities. Overall, the simulations captured the gross features of the flow, but resolving all the details which would be necessary to compute the noise remains challenging. In particular, how to best simulate the effects of the experimental transition strip, and the associated high Reynolds number effects, was unclear. Furthermore, capturing the spanwise variation proved difficult.

  3. The Prediction of Scattered Broadband Shock-Associated Noise

    NASA Technical Reports Server (NTRS)

    Miller, Steven A. E.

    2015-01-01

    A mathematical model is developed for the prediction of scattered broadband shock-associated noise. Model arguments are dependent on the vector Green's function of the linearized Euler equations, steady Reynolds-averaged Navier-Stokes solutions, and the two-point cross-correlation of the equivalent source. The equivalent source is dependent on steady Reynolds-averaged Navier-Stokes solutions of the jet flow, that capture the nozzle geometry and airframe surface. Contours of the time-averaged streamwise velocity component and turbulent kinetic energy are examined with varying airframe position relative to the nozzle exit. Propagation effects are incorporated by approximating the vector Green's function of the linearized Euler equations. This approximation involves the use of ray theory and an assumption that broadband shock-associated noise is relatively unaffected by the refraction of the jet shear layer. A non-dimensional parameter is proposed that quantifies the changes of the broadband shock-associated noise source with varying jet operating condition and airframe position. Scattered broadband shock-associated noise possesses a second set of broadband lobes that are due to the effect of scattering. Presented predictions demonstrate relatively good agreement compared to a wide variety of measurements.

  4. Ground shake test of the UH-60A helicopter airframe and comparison with NASTRAN finite element model predictions

    NASA Technical Reports Server (NTRS)

    Howland, G. R.; Durno, J. A.; Twomey, W. J.

    1990-01-01

    Sikorsky Aircraft, together with the other major helicopter airframe manufacturers, is engaged in a study to improve the use of finite element analysis to predict the dynamic behavior of helicopter airframes, under a rotorcraft structural dynamics program called DAMVIBS (Design Analysis Methods for VIBrationS), sponsored by the NASA-Langley. The test plan and test results are presented for a shake test of the UH-60A BLACK HAWK helicopter. A comparison is also presented of test results with results obtained from analysis using a NASTRAN finite element model.

  5. A study of the prediction of cruise noise and laminar flow control noise criteria for subsonic air transports

    NASA Technical Reports Server (NTRS)

    Swift, G.; Mungur, P.

    1979-01-01

    General procedures for the prediction of component noise levels incident upon airframe surfaces during cruise are developed. Contributing noise sources are those associated with the propulsion system, the airframe and the laminar flow control (LFC) system. Transformation procedures from the best prediction base of each noise source to the transonic cruise condition are established. Two approaches to LFC/acoustic criteria are developed. The first is a semi-empirical extension of the X-21 LFC/acoustic criteria to include sensitivity to the spectrum and directionality of the sound field. In the second, the more fundamental problem of how sound excites boundary layer disturbances is analyzed by deriving and solving an inhomogeneous Orr-Sommerfeld equation in which the source terms are proportional to the production and dissipation of sound induced fluctuating vorticity. Numerical solutions are obtained and compared with corresponding measurements. Recommendations are made to improve and validate both the cruise noise prediction methods and the LFC/acoustic criteria.

  6. Helicopter rotor trailing edge noise. [noise prediction

    NASA Technical Reports Server (NTRS)

    Schlinker, R. H.; Amier, R. K.

    1981-01-01

    A two dimensional section of a helicopter main rotor blade was tested in an acoustic wind tunnel at close to full-scale Reynolds numbers to obtain boundary layer data and acoustic data for use in developing an acoustic scaling law and testing a first principles trailing edge noise theory. Results were extended to the rotating frame coordinate system to develop a helicopter rotor trailing edge noise prediction. Comparisons of the calculated noise levels with helicopter flyover spectra demonstrate that trailing edge noise contributes significantly to the total helicopter noise spectrum at high frequencies. This noise mechanism is expected to control the minimum rotor noise. In the case of noise radiation from a local blade segment, the acoustic directivity pattern is predicted by the first principles trailing edge noise theory. Acoustic spectra are predicted by a scaling law which includes Mach number, boundary layer thickness and observer position. Spectrum shape and sound pressure level are also predicted by the first principles theory but the analysis does not predict the Strouhal value identifying the spectrum peak.

  7. What Was Learned in Predicting Slender Airframe Aerodynamics with the F16-XL Aircraft

    NASA Technical Reports Server (NTRS)

    Rizzi, Arthur; Lucking, James M.

    2014-01-01

    The CAWAPI-2 coordinated project has been underway to improve CFD predictions of slender airframe aerodynamics. The work is focused on two flow conditions and leverages a unique flight data set obtained with the F-16XL aircraft for comparison and verification. These conditions, a low-speed high angle-of-attack case and a transonic low angle-of-attack case, were selected from a prior prediction campaign wherein the CFD failed to provide acceptable results. In re-visiting these two cases, approaches for improved results include better, denser grids using more grid adaptation to local flow features as well as unsteady higher-fidelity physical modeling like hybrid RANS/URANS-LES methods. The work embodies predictions from multiple numerical formulations that are contributed from multiple organizations where some authors investigate other possible factors that could explain the discrepancies in agreement, e.g. effects due to deflected control surfaces during the flight tests, as well as static aeroelastic deflection of the outer wing. This paper presents the synthesis of all the results and findings and draws some conclusions that lead to an improved understanding of the underlying flow physics, and finally making the connections between the physics and aircraft features.

  8. Development and Calibration of a Field-Deployable Microphone Phased Array for Propulsion and Airframe Noise Flyover Measurements

    NASA Technical Reports Server (NTRS)

    Humphreys, William M., Jr.; Lockard, David P.; Khorrami, Mehdi R.; Culliton, William G.; McSwain, Robert G.; Ravetta, Patricio A.; Johns, Zachary

    2016-01-01

    A new aeroacoustic measurement capability has been developed consisting of a large channelcount, field-deployable microphone phased array suitable for airframe noise flyover measurements for a range of aircraft types and scales. The array incorporates up to 185 hardened, weather-resistant sensors suitable for outdoor use. A custom 4-mA current loop receiver circuit with temperature compensation was developed to power the sensors over extended cable lengths with minimal degradation of the signal to noise ratio and frequency response. Extensive laboratory calibrations and environmental testing of the sensors were conducted to verify the design's performance specifications. A compact data system combining sensor power, signal conditioning, and digitization was assembled for use with the array. Complementing the data system is a robust analysis system capable of near real-time presentation of beamformed and deconvolved contour plots and integrated spectra obtained from array data acquired during flyover passes. Additional instrumentation systems needed to process the array data were also assembled. These include a commercial weather station and a video monitoring / recording system. A detailed mock-up of the instrumentation suite (phased array, weather station, and data processor) was performed in the NASA Langley Acoustic Development Laboratory to vet the system performance. The first deployment of the system occurred at Finnegan Airfield at Fort A.P. Hill where the array was utilized to measure the vehicle noise from a number of sUAS (small Unmanned Aerial System) aircraft. A unique in-situ calibration method for the array microphones using a hovering aerial sound source was attempted for the first time during the deployment.

  9. Prediction of Landing Gear Noise Reduction and Comparison to Measurements

    NASA Technical Reports Server (NTRS)

    Lopes, Leonard V.

    2010-01-01

    Noise continues to be an ongoing problem for existing aircraft in flight and is projected to be a concern for next generation designs. During landing, when the engines are operating at reduced power, the noise from the airframe, of which landing gear noise is an important part, is equal to the engine noise. There are several methods of predicting landing gear noise, but none have been applied to predict the change in noise due to a change in landing gear design. The current effort uses the Landing Gear Model and Acoustic Prediction (LGMAP) code, developed at The Pennsylvania State University to predict the noise from landing gear. These predictions include the influence of noise reduction concepts on the landing gear noise. LGMAP is compared to wind tunnel experiments of a 6.3%-scale Boeing 777 main gear performed in the Quiet Flow Facility (QFF) at NASA Langley. The geometries tested in the QFF include the landing gear with and without a toboggan fairing and the door. It is shown that LGMAP is able to predict the noise directives and spectra from the model-scale test for the baseline configuration as accurately as current gear prediction methods. However, LGMAP is also able to predict the difference in noise caused by the toboggan fairing and by removing the landing gear door. LGMAP is also compared to far-field ground-based flush-mounted microphone measurements from the 2005 Quiet Technology Demonstrator 2 (QTD 2) flight test. These comparisons include a Boeing 777-300ER with and without a toboggan fairing that demonstrate that LGMAP can be applied to full-scale flyover measurements. LGMAP predictions of the noise generated by the nose gear on the main gear measurements are also shown.

  10. Multi-scale mechanism based life prediction of polymer matrix composites for high temperature airframe applications

    NASA Astrophysics Data System (ADS)

    Upadhyaya, Priyank

    A multi-scale mechanism-based life prediction model is developed for high-temperature polymer matrix composites (HTPMC) for high temperature airframe applications. In the first part of this dissertation the effect of Cloisite 20A (C20A) nano-clay compounding on the thermo-oxidative weight loss and the residual stresses due to thermal oxidation for a thermoset polymer bismaleimide (BMI) are investigated. A three-dimensional (3-D) micro-mechanics based finite element analysis (FEA) was conducted to investigate the residual stresses due to thermal oxidation using an in-house FEA code (NOVA-3D). In the second part of this dissertation, a novel numerical-experimental methodology is outlined to determine cohesive stress and damage evolution parameters for pristine as well as isothermally aged (in air) polymer matrix composites. A rate-dependent viscoelastic cohesive layer model was implemented in an in-house FEA code to simulate the delamination initiation and propagation in unidirectional polymer composites before and after aging. Double cantilever beam (DCB) experiments were conducted (at UT-Dallas) on both pristine and isothermally aged IM-7/BMI composite specimens to determine the model parameters. The J-Integral based approach was adapted to extract cohesive stresses near the crack tip. Once the damage parameters had been characterized, the test-bed FEA code employed a micromechanics based viscoelastic cohesive layer model to numerically simulate the DCB experiment. FEA simulation accurately captures the macro-scale behavior (load-displacement history) simultaneously with the micro-scale behavior (crack-growth history).

  11. Near-field noise prediction for aircraft in cruising flight: Methods manual. [laminar flow control noise effects analysis

    NASA Technical Reports Server (NTRS)

    Tibbetts, J. G.

    1979-01-01

    Methods for predicting noise at any point on an aircraft while the aircraft is in a cruise flight regime are presented. Developed for use in laminar flow control (LFC) noise effects analyses, they can be used in any case where aircraft generated noise needs to be evaluated at a location on an aircraft while under high altitude, high speed conditions. For each noise source applicable to the LFC problem, a noise computational procedure is given in algorithm format, suitable for computerization. Three categories of noise sources are covered: (1) propulsion system, (2) airframe, and (3) LFC suction system. In addition, procedures are given for noise modifications due to source soundproofing and the shielding effects of the aircraft structure wherever needed. Sample cases, for each of the individual noise source procedures, are provided to familiarize the user with typical input and computed data.

  12. Increased Fidelity in Prediction Methods For Landing Gear Noise

    NASA Technical Reports Server (NTRS)

    Lopes, Leonard V.; Brentner, Kenneth S.; Morris, Philip J.; Lockhard, David P.

    2006-01-01

    An aeroacoustic prediction scheme has been developed for landing gear noise. The method is designed to handle the complex landing gear geometry of current and future aircraft. The gear is represented by a collection of subassemblies and simple components that are modeled using acoustic elements. These acoustic elements are generic, but generate noise representative of the physical components on a landing gear. The method sums the noise radiation from each component of the undercarriage in isolation accounting for interference with adjacent components through an estimate of the local upstream and downstream flows and turbulence intensities. The acoustic calculations are made in the code LGMAP, which computes the sound pressure levels at various observer locations. The method can calculate the noise from the undercarriage in isolation or installed on an aircraft for both main and nose landing gear. Comparisons with wind tunnel and flight data are used to initially calibrate the method, then it may be used to predict the noise of any landing gear. In this paper, noise predictions are compared with wind tunnel data for model landing gears of various scales and levels of fidelity, as well as with flight data on fullscale undercarriages. The present agreement between the calculations and measurements suggests the method has promise for future application in the prediction of airframe noise.

  13. Auralization of Hybrid Wing Body Aircraft Flyover Noise from System Noise Predictions

    NASA Technical Reports Server (NTRS)

    Rizzi, Stephen A.; Aumann, Aric R.; Lopes, Leonvard V.; Burley, Casey L.

    2013-01-01

    System noise assessments of a state-of-the-art reference aircraft (similar to a Boeing 777-200ER with GE90-like turbofan engines) and several hybrid wing body (HWB) aircraft configurations were recently performed using NASA engine and aircraft system analysis tools. The HWB aircraft were sized to an equivalent mission as the reference aircraft and assessments were performed using measurements of airframe shielding from a series of propulsion airframe aeroacoustic experiments. The focus of this work is to auralize flyover noise from the reference aircraft and the best HWB configuration using source noise predictions and shielding data based largely on the earlier assessments. For each aircraft, three flyover conditions are auralized. These correspond to approach, sideline, and cutback operating states, but flown in straight and level flight trajectories. The auralizations are performed using synthesis and simulation tools developed at NASA. Audio and visual presentations are provided to allow the reader to experience the flyover from the perspective of a listener in the simulated environment.

  14. Predicting Noise From Wind Turbines

    NASA Technical Reports Server (NTRS)

    Grosveld, Ferdinand W.

    1990-01-01

    Computer program WINDY predicts broadband noise spectra of horizontal-axis wind-turbine generators. Enables adequate assessment of impact of broadband wind-turbine noise. Effects of turbulence, trailing-edge wakes, and bluntness taken into account. Program has practical application in design and siting of wind-turbine machines acceptable to community. Written in GW-Basic.

  15. Tandem Cylinder Noise Predictions

    NASA Technical Reports Server (NTRS)

    Lockhard, David P.; Khorrami, Mehdi R.; CHoudhari, Meelan M.; Hutcheson, Florence V.; Brooks, Thomas F.; Stead, Daniel J.

    2007-01-01

    In an effort to better understand landing-gear noise sources, we have been examining a simplified configuration that still maintains some of the salient features of landing-gear flow fields. In particular, tandem cylinders have been studied because they model a variety of component level interactions. The present effort is directed at the case of two identical cylinders spatially separated in the streamwise direction by 3.7 diameters. Experimental measurements from the Basic Aerodynamic Research Tunnel (BART) and Quiet Flow Facility (QFF) at NASA Langley Research Center (LaRC) have provided steady surface pressures, detailed off-surface measurements of the flow field using Particle Image Velocimetry (PIV), hot-wire measurements in the wake of the rear cylinder, unsteady surface pressure data, and the radiated noise. The experiments were conducted at a Reynolds number of 166 105 based on the cylinder diameter. A trip was used on the upstream cylinder to insure a fully turbulent shedding process and simulate the effects of a high Reynolds number flow. The parallel computational effort uses the three-dimensional Navier-Stokes solver CFL3D with a hybrid, zonal turbulence model that turns off the turbulence production term everywhere except in a narrow ring surrounding solid surfaces. The current calculations further explore the influence of the grid resolution and spanwise extent on the flow and associated radiated noise. Extensive comparisons with the experimental data are used to assess the ability of the computations to simulate the details of the flow. The results show that the pressure fluctuations on the upstream cylinder, caused by vortex shedding, are smaller than those generated on the downstream cylinder by wake interaction. Consequently, the downstream cylinder dominates the noise radiation, producing an overall directivity pattern that is similar to that of an isolated cylinder. Only calculations based on the full length of the model span were able to

  16. Airframe-propulsion system aerodynamic interference predictions at high transonic Mach numbers including off-design engine airflow effects

    NASA Technical Reports Server (NTRS)

    Kulfan, R. M.; Sigalla, A.

    1981-01-01

    The transonic speed regime for airplanes at conditions where inlet spillage takes place is discussed. A wind tunnel test program to evaluate aerodynamic performance penalties associated with propulsion system installation and operation at subsonic through low supersonic speeds was conducted. The accuracy of analytic methods for predicting transonic engine airframe interference effects was assessed. Study variables included Mach number, angle of attack, relative nacelle location, and nacelle mass flow ratio. Results include test theory comparisons of forces as well as induced pressure fields. Prediction capability of induced shock wave strength and locations is assessed. It was found that large interference forces due to engine location and flow spillage occur at transonic speeds, that theory explains these effects; and that theory can predict quantitatively these effects.

  17. Airframe/TPS Session

    NASA Technical Reports Server (NTRS)

    Welch, Sharon; Bowles, David

    2000-01-01

    This viewgraph presentation gives an overview of the second generation Reusable Launch Vehicle (RLV) airframe configuration, including details on the structures and materials, tanks, airframe/cryotank demonstrations, internal assemblies, weight growth and margin, and safety and cost requirements.

  18. Jet Engine Noise Generation, Prediction and Control. Chapter 86

    NASA Technical Reports Server (NTRS)

    Huff, Dennis L.; Envia, Edmane

    2004-01-01

    Aircraft noise has been a problem near airports for many years. It is a quality of life issue that impacts millions of people around the world. Solving this problem has been the principal goal of noise reduction research that began when commercial jet travel became a reality. While progress has been made in reducing both airframe and engine noise, historically, most of the aircraft noise reduction efforts have concentrated on the engines. This was most evident during the 1950 s and 1960 s when turbojet engines were in wide use. This type of engine produces high velocity hot exhaust jets during takeoff generating a great deal of noise. While there are fewer commercial aircraft flying today with turbojet engines, supersonic aircraft including high performance military aircraft use engines with similar exhaust flow characteristics. The Pratt & Whitney F100-PW-229, pictured in Figure la, is an example of an engine that powers the F-15 and F-16 fighter jets. The turbofan engine was developed for subsonic transports, which in addition to better fuel efficiency also helped mitigate engine noise by reducing the jet exhaust velocity. These engines were introduced in the late 1960 s and power most of the commercial fleet today. Over the years, the bypass ratio (that is the ratio of the mass flow through the fan bypass duct to the mass flow through the engine core) has increased to values approaching 9 for modern turbofans such as the General Electric s GE-90 engine (Figure lb). The benefits to noise reduction for high bypass ratio (HPBR) engines are derived from lowering the core jet velocity and temperature, and lowering the tip speed and pressure ratio of the fan, both of which are the consequences of the increase in bypass ratio. The HBPR engines are typically very large in diameter and can produce over 100,000 pounds of thrust for the largest engines. A third type of engine flying today is the turbo-shaft which is mainly used to power turboprop aircraft and helicopters

  19. A Process for Assessing NASA's Capability in Aircraft Noise Prediction Technology

    NASA Technical Reports Server (NTRS)

    Dahl, Milo D.

    2008-01-01

    An acoustic assessment is being conducted by NASA that has been designed to assess the current state of the art in NASA s capability to predict aircraft related noise and to establish baselines for gauging future progress in the field. The process for determining NASA s current capabilities includes quantifying the differences between noise predictions and measurements of noise from experimental tests. The computed noise predictions are being obtained from semi-empirical, analytical, statistical, and numerical codes. In addition, errors and uncertainties are being identified and quantified both in the predictions and in the measured data to further enhance the credibility of the assessment. The content of this paper contains preliminary results, since the assessment project has not been fully completed, based on the contributions of many researchers and shows a select sample of the types of results obtained regarding the prediction of aircraft noise at both the system and component levels. The system level results are for engines and aircraft. The component level results are for fan broadband noise, for jet noise from a variety of nozzles, and for airframe noise from flaps and landing gear parts. There are also sample results for sound attenuation in lined ducts with flow and the behavior of acoustic lining in ducts.

  20. Prediction of Externally Blown Flap Noise and Turbomachinery Strut Noise

    NASA Technical Reports Server (NTRS)

    Fink, M. R.

    1975-01-01

    Methods were developed for predicting externally blown flap (EBF) noise and turbomachinery strut noise. Noise radiated by under-the-wing and upper-surface-blowing EBF configurations is calculated as a sum of lift dipole noise, trailing edge noise, and jet quadrupole noise. Resulting predictions of amplitudes and spectra generally were in good agreement with data from small-scale models. These data cover a range of exhaust velocity, flap deflection, exhaust nozzle position, exhaust nozzle shape, and ratio of exhaust nozzle diameter to wing chord. A semi-empirical method for predicting dipole noise radiation from a strut with incident turbulence was in good agreement with data. Leading-edge regions made of perforated plate backed by a bulk acoustic absorber achieved up to 7 db reduction of strut noise caused by incident turbulence at high frequencies. Radial turbulence in a turbofan exit duct was found to have a relatively high level associated with the mean velocity defect in the rotor blade wakes. Use of these turbulence spectra and a dipole noise radiation equation gave general prediction of measured aft-radiated sound power caused by a splitter ring in a full-scale fan exit duct.

  1. Aircraft noise prediction program theoretical manual: Rotorcraft System Noise Prediction System (ROTONET), part 4

    NASA Technical Reports Server (NTRS)

    Weir, Donald S.; Jumper, Stephen J.; Burley, Casey L.; Golub, Robert A.

    1995-01-01

    This document describes the theoretical methods used in the rotorcraft noise prediction system (ROTONET), which is a part of the NASA Aircraft Noise Prediction Program (ANOPP). The ANOPP code consists of an executive, database manager, and prediction modules for jet engine, propeller, and rotor noise. The ROTONET subsystem contains modules for the prediction of rotor airloads and performance with momentum theory and prescribed wake aerodynamics, rotor tone noise with compact chordwise and full-surface solutions to the Ffowcs-Williams-Hawkings equations, semiempirical airfoil broadband noise, and turbulence ingestion broadband noise. Flight dynamics, atmosphere propagation, and noise metric calculations are covered in NASA TM-83199, Parts 1, 2, and 3.

  2. Fan Noise Prediction with Applications to Aircraft System Noise Assessment

    NASA Technical Reports Server (NTRS)

    Nark, Douglas M.; Envia, Edmane; Burley, Casey L.

    2009-01-01

    This paper describes an assessment of current fan noise prediction tools by comparing measured and predicted sideline acoustic levels from a benchmark fan noise wind tunnel test. Specifically, an empirical method and newly developed coupled computational approach are utilized to predict aft fan noise for a benchmark test configuration. Comparisons with sideline noise measurements are performed to assess the relative merits of the two approaches. The study identifies issues entailed in coupling the source and propagation codes, as well as provides insight into the capabilities of the tools in predicting the fan noise source and subsequent propagation and radiation. In contrast to the empirical method, the new coupled computational approach provides the ability to investigate acoustic near-field effects. The potential benefits/costs of these new methods are also compared with the existing capabilities in a current aircraft noise system prediction tool. The knowledge gained in this work provides a basis for improved fan source specification in overall aircraft system noise studies.

  3. Flyover-noise measurement and prediction

    NASA Technical Reports Server (NTRS)

    Peart, Noel A.

    1991-01-01

    Details are presented for the measurement and prediction of aircraft flyover noise to be used for certification, research and development, community noise surveys, airport monitors, and pass fail criteria. Test details presented are applicable to all types of aircraft, both large and small, and the use of Federal Aviation Regulations (FAR) Part 36 (ref. 1) is emphasized. Accuracy of noise measurements is important. Thus, a pass-fail criterion should be used for all noise measurements. Finally, factors which influence the sound propagation and noise prediction procedures, such as atmospheric and ground effects, are also presented.

  4. Predicting Anthropogenic Noise Contributions to US Waters.

    PubMed

    Gedamke, Jason; Ferguson, Megan; Harrison, Jolie; Hatch, Leila; Henderson, Laurel; Porter, Michael B; Southall, Brandon L; Van Parijs, Sofie

    2016-01-01

    To increase understanding of the potential effects of chronic underwater noise in US waters, the National Oceanic and Atmospheric Administration (NOAA) organized two working groups in 2011, collectively called "CetSound," to develop tools to map the density and distribution of cetaceans (CetMap) and predict the contribution of human activities to underwater noise (SoundMap). The SoundMap effort utilized data on density, distribution, acoustic signatures of dominant noise sources, and environmental descriptors to map estimated temporal, spatial, and spectral contributions to background noise. These predicted soundscapes are an initial step toward assessing chronic anthropogenic noise impacts on the ocean's varied acoustic habitats and the animals utilizing them.

  5. Aircraft Noise Prediction Program theoretical manual: Propeller aerodynamics and noise

    NASA Technical Reports Server (NTRS)

    Zorumski, W. E. (Editor); Weir, D. S. (Editor)

    1986-01-01

    The prediction sequence used in the aircraft noise prediction program (ANOPP) is described. The elements of the sequence are called program modules. The first group of modules analyzes the propeller geometry, the aerodynamics, including both potential and boundary-layer flow, the propeller performance, and the surface loading distribution. This group of modules is based entirely on aerodynamic strip theory. The next group of modules deals with the first group. Predictions of periodic thickness and loading noise are determined with time-domain methods. Broadband noise is predicted by a semiempirical method. Near-field predictions of fuselage surface pressrues include the effects of boundary layer refraction and scattering. Far-field predictions include atmospheric and ground effects.

  6. Empirical Prediction of Aircraft Landing Gear Noise

    NASA Technical Reports Server (NTRS)

    Golub, Robert A. (Technical Monitor); Guo, Yue-Ping

    2005-01-01

    This report documents a semi-empirical/semi-analytical method for landing gear noise prediction. The method is based on scaling laws of the theory of aerodynamic noise generation and correlation of these scaling laws with current available test data. The former gives the method a sound theoretical foundation and the latter quantitatively determines the relations between the parameters of the landing gear assembly and the far field noise, enabling practical predictions of aircraft landing gear noise, both for parametric trends and for absolute noise levels. The prediction model is validated by wind tunnel test data for an isolated Boeing 737 landing gear and by flight data for the Boeing 777 airplane. In both cases, the predictions agree well with data, both in parametric trends and in absolute noise levels.

  7. Landing-gear noise prediction using high-order finite difference schemes

    NASA Astrophysics Data System (ADS)

    Liu, Wen; Wook Kim, Jae; Zhang, Xin; Angland, David; Caruelle, Bastien

    2013-07-01

    Aerodynamic noise from a generic two-wheel landing-gear model is predicted by a CFD/FW-H hybrid approach. The unsteady flow-field is computed using a compressible Navier-Stokes solver based on high-order finite difference schemes and a fully structured grid. The calculated time history of the surface pressure data is used in an FW-H solver to predict the far-field noise levels. Both aerodynamic and aeroacoustic results are compared to wind tunnel measurements and are found to be in good agreement. The far-field noise was found to vary with the 6th power of the free-stream velocity. Individual contributions from three components, i.e. wheels, axle and strut of the landing-gear model are also investigated to identify the relative contribution to the total noise by each component. It is found that the wheels are the dominant noise source in general. Strong vortex shedding from the axle is the second major contributor to landing-gear noise. This work is part of Airbus LAnding Gear nOise database for CAA validatiON (LAGOON) program with the general purpose of evaluating current CFD/CAA and experimental techniques for airframe noise prediction.

  8. Status of ERA Airframe Technology Demonstrators

    NASA Technical Reports Server (NTRS)

    Davis, Pamela; Jegley, Dawn; Rigney, Tom

    2015-01-01

    NASA has created the Environmentally Responsible Aviation (ERA) Project to explore and document the feasibility, benefits and technical risk of advanced vehicle configurations and enabling technologies that will reduce the impact of aviation on the environment. A critical aspect of this pursuit is the development of a lighter, more robust airframe that will enable the introduction of unconventional aircraft configurations that have higher lift-to-drag ratios, reduced drag, and lower community noise. The Airframe Technology subproject contains two elements. Under the Damage Arresting Composite Demonstration an advanced material system is being explored which will lead to lighter airframes that are more structural efficient than the composites used in aircraft today. Under the Adaptive Compliant Trailing Edge Flight Experiment a new concept of a flexible wing trailing edge is being evaluated which will reduce weight and improve aerodynamic performance. This presentation will describe the development these two airframe technologies.

  9. Airfoil self-noise and prediction

    NASA Technical Reports Server (NTRS)

    Brooks, Thomas F.; Pope, D. Stuart; Marcolini, Michael A.

    1989-01-01

    A prediction method is developed for the self-generated noise of an airfoil blade encountering smooth flow. The prediction methods for the individual self-noise mechanisms are semiempirical and are based on previous theoretical studies and data obtained from tests of two- and three-dimensional airfoil blade sections. The self-noise mechanisms are due to specific boundary-layer phenomena, that is, the boundary-layer turbulence passing the trailing edge, separated-boundary-layer and stalled flow over an airfoil, vortex shedding due to laminar boundary layer instabilities, vortex shedding from blunt trailing edges, and the turbulent vortex flow existing near the tip of lifting blades. The predictions are compared successfully with published data from three self-noise studies of different airfoil shapes. An application of the prediction method is reported for a large scale-model helicopter rotor, and the predictions compared well with experimental broadband noise measurements. A computer code of the method is given.

  10. Fuel Efficiencies Through Airframe Improvements

    NASA Technical Reports Server (NTRS)

    Bezos-O'Connor, Gaudy M.; Mangelsdorf, Mark F.; Maliska, Heather A.; Washburn, Anthony E.; Wahls, Richard A.

    2011-01-01

    The factors of continuing strong growth in air traffic volume, the vital role of the air transport system on the economy, and concerns about the environmental impact of aviation have added focus to the National Aeronautics Research Policy. To address these concerns in the context of the National Policy, NASA has set aggressive goals in noise reduction, emissions, and energy consumption. With respect to the goal of reducing energy consumption in the fleet, the development of promising airframe technologies is required to realize the significant improvements that are desired. Furthermore, the combination of advances in materials and structures with aerodynamic technologies may lead to a paradigm shift in terms of potential configurations for the future. Some of these promising airframe technologies targeted at improved efficiency are highlighted.

  11. A computer program for the prediction of near field noise of aircraft in cruising flight: User's guide

    NASA Technical Reports Server (NTRS)

    Tibbetts, J. G.

    1980-01-01

    Detailed instructions for using the near field cruise noise prediction program, a program listing, and a sample case with output are presented. The total noise for free field lossless conditions at selected observer locations is obtained by summing the contributions from up to nine acoustic sources. These noise sources, selected at the user's option, include the fan/compressor, turbine, core (combustion), jet, shock, and airframe (trailing edge and turbulent boundary layers). The effects of acoustic suppression materials such as engine inlet treatment may also be included in the noise prediction. The program is available for use on the NASA/Langley Research Center CDC computer. Comparisons of the program predictions with measured data are also given, and some possible reasons for their lack of agreement presented.

  12. Assessment of Current Jet Noise Prediction Capabilities

    NASA Technical Reports Server (NTRS)

    Hunter, Craid A.; Bridges, James E.; Khavaran, Abbas

    2008-01-01

    An assessment was made of the capability of jet noise prediction codes over a broad range of jet flows, with the objective of quantifying current capabilities and identifying areas requiring future research investment. Three separate codes in NASA s possession, representative of two classes of jet noise prediction codes, were evaluated, one empirical and two statistical. The empirical code is the Stone Jet Noise Module (ST2JET) contained within the ANOPP aircraft noise prediction code. It is well documented, and represents the state of the art in semi-empirical acoustic prediction codes where virtual sources are attributed to various aspects of noise generation in each jet. These sources, in combination, predict the spectral directivity of a jet plume. A total of 258 jet noise cases were examined on the ST2JET code, each run requiring only fractions of a second to complete. Two statistical jet noise prediction codes were also evaluated, JeNo v1, and Jet3D. Fewer cases were run for the statistical prediction methods because they require substantially more resources, typically a Reynolds-Averaged Navier-Stokes solution of the jet, volume integration of the source statistical models over the entire plume, and a numerical solution of the governing propagation equation within the jet. In the evaluation process, substantial justification of experimental datasets used in the evaluations was made. In the end, none of the current codes can predict jet noise within experimental uncertainty. The empirical code came within 2dB on a 1/3 octave spectral basis for a wide range of flows. The statistical code Jet3D was within experimental uncertainty at broadside angles for hot supersonic jets, but errors in peak frequency and amplitude put it out of experimental uncertainty at cooler, lower speed conditions. Jet3D did not predict changes in directivity in the downstream angles. The statistical code JeNo,v1 was within experimental uncertainty predicting noise from cold subsonic

  13. Predicting Anthropogenic Noise Contributions to US Waters.

    PubMed

    Gedamke, Jason; Ferguson, Megan; Harrison, Jolie; Hatch, Leila; Henderson, Laurel; Porter, Michael B; Southall, Brandon L; Van Parijs, Sofie

    2016-01-01

    To increase understanding of the potential effects of chronic underwater noise in US waters, the National Oceanic and Atmospheric Administration (NOAA) organized two working groups in 2011, collectively called "CetSound," to develop tools to map the density and distribution of cetaceans (CetMap) and predict the contribution of human activities to underwater noise (SoundMap). The SoundMap effort utilized data on density, distribution, acoustic signatures of dominant noise sources, and environmental descriptors to map estimated temporal, spatial, and spectral contributions to background noise. These predicted soundscapes are an initial step toward assessing chronic anthropogenic noise impacts on the ocean's varied acoustic habitats and the animals utilizing them. PMID:26610977

  14. Developing and utilizing an Euler computational method for predicting the airframe/propulsion effects for an aft-mounted turboprop transport. Volume 2: User guide

    NASA Technical Reports Server (NTRS)

    Chen, H. C.; Neback, H. E.; Kao, T. J.; Yu, N. Y.; Kusunose, K.

    1991-01-01

    This manual explains how to use an Euler based computational method for predicting the airframe/propulsion integration effects for an aft-mounted turboprop transport. The propeller power effects are simulated by the actuator disk concept. This method consists of global flow field analysis and the embedded flow solution for predicting the detailed flow characteristics in the local vicinity of an aft-mounted propfan engine. The computational procedure includes the use of several computer programs performing four main functions: grid generation, Euler solution, grid embedding, and streamline tracing. This user's guide provides information for these programs, including input data preparations with sample input decks, output descriptions, and sample Unix scripts for program execution in the UNICOS environment.

  15. Aircraft Noise Prediction Program (ANOPP) Fan Noise Prediction for Small Engines

    NASA Technical Reports Server (NTRS)

    Hough, Joe W.; Weir, Donald S.

    1996-01-01

    The Fan Noise Module of ANOPP is used to predict the broadband noise and pure tones for axial flow compressors or fans. The module, based on the method developed by M. F. Heidmann, uses empirical functions to predict fan noise spectra as a function of frequency and polar directivity. Previous studies have determined the need to modify the module to better correlate measurements of fan noise from engines in the 3000- to 6000-pound thrust class. Additional measurements made by AlliedSignal have confirmed the need to revise the ANOPP fan noise method for smaller engines. This report describes the revisions to the fan noise method which have been verified with measured data from three separate AlliedSignal fan engines. Comparisons of the revised prediction show a significant improvement in overall and spectral noise predictions.

  16. Advances in tilt rotor noise prediction

    NASA Technical Reports Server (NTRS)

    George, A. R.; Coffen, C. D.; Ringler, T. D.

    1992-01-01

    The two most serious tilt rotor external noise problems, hover noise and blade-vortex interaction noise, are studied. The results of flow visualization and inflow velocity measurements document a complex, recirculating highly unsteady and turbulent flow due to the rotor-wing-body interactions characteristic of tilt rotors. The wing under the rotor is found to obstruct the inflow, causing a deficit in the inflow velocities over the inboard region of the rotor. Discrete frequency harmonic thickness and loading noise mechanisms in hover are examined by first modeling tilt rotor hover aerodynamics and then applying various noise prediction methods using the WOPWOP code. The analysis indicates that the partial ground plane created by the wing below the rotor results in a primary sound source for hover.

  17. Advances in tilt rotor noise prediction

    NASA Astrophysics Data System (ADS)

    George, A. R.; Coffen, C. D.; Ringler, T. D.

    The two most serious tilt rotor external noise problems, hover noise and blade-vortex interaction noise, are studied. The results of flow visualization and inflow velocity measurements document a complex, recirculating highly unsteady and turbulent flow due to the rotor-wing-body interactions characteristic of tilt rotors. The wing under the rotor is found to obstruct the inflow, causing a deficit in the inflow velocities over the inboard region of the rotor. Discrete frequency harmonic thickness and loading noise mechanisms in hover are examined by first modeling tilt rotor hover aerodynamics and then applying various noise prediction methods using the WOPWOP code. The analysis indicates that the partial ground plane created by the wing below the rotor results in a primary sound source for hover.

  18. Validation of helicopter noise prediction techniques

    NASA Technical Reports Server (NTRS)

    Succi, G. P.

    1981-01-01

    The current techniques of helicopter rotor noise prediction attempt to describe the details of the noise field precisely and remove the empiricisms and restrictions inherent in previous methods. These techniques require detailed inputs of the rotor geometry, operating conditions, and blade surface pressure distribution. The purpose of this paper is to review those techniques in general and the Farassat/Nystrom analysis in particular. The predictions of the Farassat/Nystrom noise computer program, using both measured and calculated blade surface pressure data, are compared to measured noise level data. This study is based on a contract from NASA to Bolt Beranek and Newman Inc. with measured data from the AH-1G Helicopter Operational Loads Survey flight test program supplied by Bell Helicopter Textron.

  19. Jet Aeroacoustics: Noise Generation Mechanism and Prediction

    NASA Technical Reports Server (NTRS)

    Tam, Christopher

    1998-01-01

    This report covers the third year research effort of the project. The research work focussed on the fine scale mixing noise of both subsonic and supersonic jets and the effects of nozzle geometry and tabs on subsonic jet noise. In publication 1, a new semi-empirical theory of jet mixing noise from fine scale turbulence is developed. By an analogy to gas kinetic theory, it is shown that the source of noise is related to the time fluctuations of the turbulence kinetic theory. On starting with the Reynolds Averaged Navier-Stokes equations, a formula for the radiated noise is derived. An empirical model of the space-time correlation function of the turbulence kinetic energy is adopted. The form of the model is in good agreement with the space-time two-point velocity correlation function measured by Davies and coworkers. The parameters of the correlation are related to the parameters of the k-epsilon turbulence model. Thus the theory is self-contained. Extensive comparisons between the computed noise spectrum of the theory and experimental measured have been carried out. The parameters include jet Mach number from 0.3 to 2.0 and temperature ratio from 1.0 to 4.8. Excellent agreements are found in the spectrum shape, noise intensity and directivity. It is envisaged that the theory would supercede all semi-empirical and totally empirical jet noise prediction methods in current use.

  20. Prediction of light aircraft interior noise

    NASA Technical Reports Server (NTRS)

    Howlett, J. T.; Morales, D. A.

    1976-01-01

    At the present time, predictions of aircraft interior noise depend heavily on empirical correction factors derived from previous flight measurements. However, to design for acceptable interior noise levels and to optimize acoustic treatments, analytical techniques which do not depend on empirical data are needed. This paper describes a computerized interior noise prediction method for light aircraft. An existing analytical program (developed for commercial jets by Cockburn and Jolly in 1968) forms the basis of some modal analysis work which is described. The accuracy of this modal analysis technique for predicting low-frequency coupled acoustic-structural natural frequencies is discussed along with trends indicating the effects of varying parameters such as fuselage length and diameter, structural stiffness, and interior acoustic absorption.

  1. Computational Analysis of a Chevron Nozzle Uniquely Tailored for Propulsion Airframe Aeroacoustics

    NASA Technical Reports Server (NTRS)

    Massey, Steven J.; Elmiligui, Alaa A.; Hunter, Craig A.; Thomas, Russell H.; Pao, S. Paul; Mengle, Vinod G.

    2006-01-01

    A computational flow field and predicted jet noise source analysis is presented for asymmetrical fan chevrons on a modern separate flow nozzle at take off conditions. The propulsion airframe aeroacoustic asymmetric fan nozzle is designed with an azimuthally varying chevron pattern with longer chevrons close to the pylon. A baseline round nozzle without chevrons and a reference nozzle with azimuthally uniform chevrons are also studied. The intent of the asymmetric fan chevron nozzle was to improve the noise reduction potential by creating a favorable propulsion airframe aeroacoustic interaction effect between the pylon and chevron nozzle. This favorable interaction and improved noise reduction was observed in model scale tests and flight test data and has been reported in other studies. The goal of this study was to identify the fundamental flow and noise source mechanisms. The flow simulation uses the asymptotically steady, compressible Reynolds averaged Navier-Stokes equations on a structured grid. Flow computations are performed using the parallel, multi-block, structured grid code PAB3D. Local noise sources were mapped and integrated computationally using the Jet3D code based upon the Lighthill Acoustic Analogy with anisotropic Reynolds stress modeling. In this study, trends of noise reduction were correctly predicted. Jet3D was also utilized to produce noise source maps that were then correlated to local flow features. The flow studies show that asymmetry of the longer fan chevrons near the pylon work to reduce the strength of the secondary flow induced by the pylon itself, such that the asymmetric merging of the fan and core shear layers is significantly delayed. The effect is to reduce the peak turbulence kinetic energy and shift it downstream, reducing overall noise production. This combined flow and noise prediction approach has yielded considerable understanding of the physics of a fan chevron nozzle designed to include propulsion airframe aeroacoustic

  2. Aircraft noise prediction program user's manual

    NASA Technical Reports Server (NTRS)

    Gillian, R. E.

    1982-01-01

    The Aircraft Noise Prediction Program (ANOPP) predicts aircraft noise with the best methods available. This manual is designed to give the user an understanding of the capabilities of ANOPP and to show how to formulate problems and obtain solutions by using these capabilities. Sections within the manual document basic ANOPP concepts, ANOPP usage, ANOPP functional modules, ANOPP control statement procedure library, and ANOPP permanent data base. appendixes to the manual include information on preparing job decks for the operating systems in use, error diagnostics and recovery techniques, and a glossary of ANOPP terms.

  3. Prediction of noise constrained optimum takeoff procedures

    NASA Technical Reports Server (NTRS)

    Padula, S. L.

    1980-01-01

    An optimization method is used to predict safe, maximum-performance takeoff procedures which satisfy noise constraints at multiple observer locations. The takeoff flight is represented by two-degree-of-freedom dynamical equations with aircraft angle-of-attack and engine power setting as control functions. The engine thrust, mass flow and noise source parameters are assumed to be given functions of the engine power setting and aircraft Mach number. Effective Perceived Noise Levels at the observers are treated as functionals of the control functions. The method is demonstrated by applying it to an Advanced Supersonic Transport aircraft design. The results indicate that automated takeoff procedures (continuously varying controls) can be used to significantly reduce community and certification noise without jeopardizing safety or degrading performance.

  4. Aeroacoustics of Propulsion Airframe Integration: Overview of NASA's Research

    NASA Technical Reports Server (NTRS)

    Thomas, Russell H.

    2003-01-01

    The integration of propulsion and airframe is fundamental to the design of an aircraft system. Many considerations influence the integration, such as structural, aerodynamic, and maintenance factors. In regard to the acoustics of an aircraft, the integration can have significant effects on the net radiated noise. Whether an engine is mounted above a wing or below can have a significant effect on noise that reaches communities below because of shielding or reflection of engine noise. This is an obvious example of the acoustic effects of propulsion airframe installation. Another example could be the effect of the pylon on the development of the exhaust plume and on the resulting jet noise. In addition, for effective system noise reduction the impact that installation has on noise reduction devices developed on isolated components must be understood. In the future, a focus on the aerodynamic and acoustic interaction effects of installation, propulsion airframe aeroacoustics, will become more important as noise reduction targets become more difficult to achieve. In addition to continued fundamental component reduction efforts, a system level approach that includes propulsion airframe aeroacoustics will be required in order to achieve the 20 dB of perceived noise reduction envisioned by the long-range NASA goals. This emphasis on the aeroacoustics of propulsion airframe integration is a new part of NASA s noise research. The following paper will review current efforts and highlight technical challenges and approaches.

  5. Prediction of light aircraft interior noise

    NASA Technical Reports Server (NTRS)

    Howlett, J. T.; Morales, D. A.

    1976-01-01

    A computerized interior noise prediction method for light aircraft is described. An existing analytical program, development for commercial jets, forms the basis of some modal analysis work which is described. The accuracy of this modal analysis technique for predicting low-frequency coupled acoustic-structural natural frequencies is discussed along with trends indicating the effects of varying parameters such as fuselage length and diameter, structural stiffness, and interior acoustic absorption.

  6. Jet Noise Diagnostics Supporting Statistical Noise Prediction Methods

    NASA Technical Reports Server (NTRS)

    Bridges, James E.

    2006-01-01

    The primary focus of my presentation is the development of the jet noise prediction code JeNo with most examples coming from the experimental work that drove the theoretical development and validation. JeNo is a statistical jet noise prediction code, based upon the Lilley acoustic analogy. Our approach uses time-average 2-D or 3-D mean and turbulent statistics of the flow as input. The output is source distributions and spectral directivity. NASA has been investing in development of statistical jet noise prediction tools because these seem to fit the middle ground that allows enough flexibility and fidelity for jet noise source diagnostics while having reasonable computational requirements. These tools rely on Reynolds-averaged Navier-Stokes (RANS) computational fluid dynamics (CFD) solutions as input for computing far-field spectral directivity using an acoustic analogy. There are many ways acoustic analogies can be created, each with a series of assumptions and models, many often taken unknowingly. And the resulting prediction can be easily reverse-engineered by altering the models contained within. However, only an approach which is mathematically sound, with assumptions validated and modeled quantities checked against direct measurement will give consistently correct answers. Many quantities are modeled in acoustic analogies precisely because they have been impossible to measure or calculate, making this requirement a difficult task. The NASA team has spent considerable effort identifying all the assumptions and models used to take the Navier-Stokes equations to the point of a statistical calculation via an acoustic analogy very similar to that proposed by Lilley. Assumptions have been identified and experiments have been developed to test these assumptions. In some cases this has resulted in assumptions being changed. Beginning with the CFD used as input to the acoustic analogy, models for turbulence closure used in RANS CFD codes have been explored and

  7. Helicopter Rotor Noise Prediction: Background, Current Status, and Future Direction

    NASA Technical Reports Server (NTRS)

    Brentner, Kenneth S.

    1997-01-01

    Helicopter noise prediction is increasingly important. The purpose of this viewgraph presentation is to: 1) Put into perspective the recent progress; 2) Outline current prediction capabilities; 3) Forecast direction of future prediction research; 4) Identify rotorcraft noise prediction needs. The presentation includes an historical perspective, a description of governing equations, and the current status of source noise prediction.

  8. Noise Prediction Module for Offset Stream Nozzles

    NASA Technical Reports Server (NTRS)

    Henderson, Brenda S.

    2011-01-01

    A Modern Design of Experiments (MDOE) analysis of data acquired for an offset stream technology was presented. The data acquisition and concept development were funded under a Supersonics NRA NNX07AC62A awarded to Dimitri Papamoschou at University of California, Irvine. The technology involved the introduction of airfoils in the fan stream of a bypass ratio (BPR) two nozzle system operated at transonic exhaust speeds. The vanes deflected the fan stream relative to the core stream and resulted in reduced sideline noise for polar angles in the peak jet noise direction. Noise prediction models were developed for a range of vane configurations. The models interface with an existing ANOPP module and can be used or future system level studies.

  9. Comparison of predicted engine core noise with current and proposed aircraft noise certification requirements

    NASA Technical Reports Server (NTRS)

    Vonglahn, U. H.; Groesbeck, D. E.

    1981-01-01

    Predicted engine core noise levels are compared with measured total aircraft noise levels and with current and proposed federal noise certification requirements. Comparisons are made at the FAR-36 measuring stations and include consideration of both full- and cutback-power operation at takeoff. In general, core noise provides a barrier to achieving proposed EPA stage 5 noise levels for all types of aircraft. More specifically, core noise levels will limit further reductions in aircraft noise levels for current widebody commercial aircraft.

  10. Interior noise prediction methodology: ATDAC theory and validation

    NASA Technical Reports Server (NTRS)

    Mathur, Gopal P.; Gardner, Bryce K.

    1992-01-01

    The Acoustical Theory for Design of Aircraft Cabins (ATDAC) is a computer program developed to predict interior noise levels inside aircraft and to evaluate the effects of different aircraft configurations on the aircraft acoustical environment. The primary motivation for development of this program is the special interior noise problems associated with advanced turboprop (ATP) aircraft where there is a tonal, low frequency noise problem. Prediction of interior noise levels requires knowledge of the energy sources, the transmission paths, and the relationship between the energy variable and the sound pressure level. The energy sources include engine noise, both airborne and structure-borne; turbulent boundary layer noise; and interior noise sources such as air conditioner noise and auxiliary power unit noise. Since propeller and engine noise prediction programs are widely available, they are not included in ATDAC. Airborne engine noise from any prediction or measurement may be input to this program. This report describes the theory and equations implemented in the ATDAC program.

  11. Supersonic Coaxial Jets: Noise Predictions and Measurements

    NASA Technical Reports Server (NTRS)

    Dahl, Milo D.; Papamoschou, Dimitri; Hixon, Ray

    1998-01-01

    The noise from perfectly expanded coaxial jets was measured in an anechoic chamber for different operating conditions with the same total thrust, mass flow, and exit area. The shape of the measured noise spectrum at different angles to the jet axis was found to agree with spectral shapes for single, axisymmetric jets. Based on these spectra, the sound was characterized as being generated by large turbulent structures or fine-scale turbulence. Modeling the large scale structures as instability waves, a stability analysis was conducted for the coaxial jets to identify the growing and decaying instability waves in each shear layer and predict their noise radiation pattern outside the jet. When compared to measured directivity, the analysis identified the region downstream of the outer potential core, where the two shear layers were merging, as the source of the peak radiated noise where instability waves, with their origin in the inner shear layer, reach their maximum amplitude. Numerical computations were also performed using a linearized Euler equation solver. Those results were compared to both the results from the instability wave analysis and to measured data.

  12. A noise assessment and prediction system

    NASA Astrophysics Data System (ADS)

    Olsen, Robert O.; Noble, John M.

    1990-12-01

    A system has been designed to provide an assessment of noise levels that result from testing activities at Aberdeen Proving Ground, Md. The system receives meteorological data from surface stations and an upper air sounding system. The data from these systems are sent to a meteorological model, which provides forecasting conditions for up to three hours from the test time. The meteorological data are then used as input into an acoustic ray trace model which projects sound level contours onto a two-dimensional display of the surrounding area. This information is sent to the meteorological office for verification, as well as the range control office, and the environmental office. To evaluate the noise level predictions, a series of microphones are located off the reservation to receive the sound and transmit this information back to the central display unit. The computer models are modular allowing for a variety of models to be utilized and tested to achieve the best agreement with data. This technique of prediction and model validation will be used to improve the noise assessment system.

  13. A noise assessment and prediction system

    NASA Technical Reports Server (NTRS)

    Olsen, Robert O.; Noble, John M.

    1990-01-01

    A system has been designed to provide an assessment of noise levels that result from testing activities at Aberdeen Proving Ground, Md. The system receives meteorological data from surface stations and an upper air sounding system. The data from these systems are sent to a meteorological model, which provides forecasting conditions for up to three hours from the test time. The meteorological data are then used as input into an acoustic ray trace model which projects sound level contours onto a two-dimensional display of the surrounding area. This information is sent to the meteorological office for verification, as well as the range control office, and the environmental office. To evaluate the noise level predictions, a series of microphones are located off the reservation to receive the sound and transmit this information back to the central display unit. The computer models are modular allowing for a variety of models to be utilized and tested to achieve the best agreement with data. This technique of prediction and model validation will be used to improve the noise assessment system.

  14. Preliminary thoughts on helicopter cabin noise prediction methods

    NASA Astrophysics Data System (ADS)

    Pollard, J. S.

    The problems of predicting helicopter cabin noise are discussed with particular reference to the Lynx helicopter. Available methods such as modal analysis adopted for propeller noise prediction do not cope with the higher frequency discrete tone content of helicopter gear noise, with the airborne and structureborne noise contributions. Statistical energy analysis methods may be the answer but until these are developed, one has to rely on classical noise transmission analysis and transfer function methods.

  15. A method to predict circulation control noise

    NASA Astrophysics Data System (ADS)

    Reger, Robert W.

    Underwater vehicles suffer from reduced maneuverability with conventional lifting append-\\ ages due to the low velocity of operation. Circulation control offers a method to increase maneuverability independent of vehicle speed. However, with circulation control comes additional noise sources, which are not well understood. To better understand these noise sources, a modal-based prediction method is developed, potentially offering a quantitative connection between flow structures and far-field noise. This method involves estimation of the velocity field, surface pressure field, and far-field noise, using only non-time-resolved velocity fields and time-resolved probe measurements. Proper orthogonal decomposition, linear stochastic estimation and Kalman smoothing are employed to estimate time-resolved velocity fields. Poisson's equation is used to calculate time-resolved pressure fields from velocity. Curle's analogy is then used to propagate the surface pressure forces to the far field. This method is developed on a direct numerical simulation of a two-dimensional cylinder at a low Reynolds number (150). Since each of the fields to be estimated are also known from the simulation, a means of obtaining the error from using the methodology is provided. The velocity estimation and the simulated velocity match well when the simulated additive measurement noise is low. The pressure field suffers due to a small domain size; however, the surface pressures estimates fare much better. The far-field estimation contains similar frequency content with reduced magnitudes, attributed to the exclusion of the viscous forces in Curle's analogy. In the absence of added noise, the estimation procedure performs quite nicely for this model problem. The method is tested experimentally on a 650,000 chord-Reynolds-number flow over a 2-D, 20% thick, elliptic circulation control airfoil. Slot jet momentum coefficients of 0 and 0.10 are investigated. Particle image velocimetry, unsteady

  16. Unsteady jet flow computation towards noise prediction

    NASA Technical Reports Server (NTRS)

    Soh, Woo-Yung

    1994-01-01

    An attempt has been made to combine a wave solution method and an unsteady flow computation to produce an integrated aeroacoustic code to predict far-field jet noise. An axisymmetric subsonic jet is considered for this purpose. A fourth order space accurate Pade compact scheme is used for the unsteady Navier-Stokes solution. A Kirchhoff surface integral for the wave equation is employed through the use of an imaginary surface which is a circular cylinder enclosing the jet at a distance. Information such as pressure and its time and normal derivatives is provided on the surface. The sound prediction is performed side by side with the jet flow computation. Retarded time is also taken into consideration since the cylinder body is not acoustically compact. The far-field sound pressure has the directivity and spectra show that low frequency peaks shift toward higher frequency region as the observation angle increases from the jet flow axis.

  17. NASA airframe structural integrity program

    NASA Technical Reports Server (NTRS)

    Harris, Charles E.

    1990-01-01

    NASA initiated a research program with the long-term objective of supporting the aerospace industry in addressing issues related to the aging of the commercial transport fleet. The program combines advanced fatigue crack growth prediction methodology with innovative nondestructive examination technology with the focus on multi-stage damage (MSD) at rivited connections. A fracture mechanics evaluation of the concept of pressure proof testing the fuselage to screen for MSD was completed. A successful laboratory demonstration of the ability of the thermal flux method to detect disbonds at rivited lap splice joints was conducted. All long-term program elements were initiated, and the plans for the methodology verification program are being coordinated with the airframe manufacturers.

  18. NASA airframe structural integrity program

    NASA Technical Reports Server (NTRS)

    Harris, Charles E.

    1991-01-01

    NASA has initiated a research program with the long-term objective of supporting the aerospace industry in addressing issues related to the aging commercial transport fleet. The interdisciplinary program combines advanced fatigue crack growth prediction methodology with innovative nondestructive examination technology with the focus on multi-site damage (MSD) at riveted connections. A fracture mechanics evaluation of the concept of pressure proof testing the fuselage to screen for MSD has been completed. Also, a successful laboratory demonstration of the ability of the thermal flux method to detect disbonds at riveted lap splice joints has been conducted. All long-term program elements have been initiated and the plans for the methodology verification program are being coordinated with the airframe manufacturers.

  19. Rotor Broadband Noise Prediction with Comparison to Model Data

    NASA Technical Reports Server (NTRS)

    Brooks, Thomas F.; Burley, Casey L.

    2001-01-01

    This paper reports an analysis and prediction development of rotor broadband noise. The two primary components of this noise are Blade-Wake Interaction (BWI) noise, due to the blades' interaction with the turbulent wakes of the preceding blades, and "Self" noise, due to the development and shedding of turbulence within the blades' boundary layers. Emphasized in this report is the new code development for Self noise. The analysis and validation employs data from the HART program, a model BO-105 rotor wind tunnel test conducted in the German-Dutch Wind Tunnel (DNW). The BWI noise predictions are based on measured pressure response coherence functions using cross-spectral methods. The Self noise predictions are based on previously reported semiempirical modeling of Self noise obtained from isolated airfoil sections and the use of CAMRAD.Modl to define rotor performance and local blade segment flow conditions. Both BWI and Self noise from individual blade segments are Doppler shifted and summed at the observer positions. Prediction comparisons with measurements show good agreement for a range of rotor operating conditions from climb to steep descent. The broadband noise predictions, along with those of harmonic and impulsive Blade-Vortex Interaction (BVI) noise predictions, demonstrate a significant advance in predictive capability for main rotor noise.

  20. Assessment of Slat Noise Predictions for 30P30N High-Lift Configuration From BANC-III Workshop

    NASA Technical Reports Server (NTRS)

    Choudhari, Meelan; Lockard, David P.

    2015-01-01

    This paper presents a summary of the computational predictions and measurement data contributed to Category 7 of the 3rd AIAA Workshop on Benchmark Problems for Airframe Noise Computations (BANC-III), which was held in Atlanta, GA, on June 14-15, 2014. Category 7 represents the first slat-noise configuration to be investigated under the BANC series of workshops, namely, the 30P30N two-dimensional high-lift model (with a slat contour that was slightly modified to enable unsteady pressure measurements) at an angle of attack that is relevant to approach conditions. Originally developed for a CFD challenge workshop to assess computational fluid dynamics techniques for steady high-lift predictions, the 30P30N configurations has provided a valuable opportunity for the airframe noise community to collectively assess and advance the computational and experimental techniques for slat noise. The contributed solutions are compared with each other as well as with the initial measurements that became available just prior to the BANC-III Workshop. Specific features of a number of computational solutions on the finer grids compare reasonably well with the initial measurements from FSU and JAXA facilities and/or with each other. However, no single solution (or a subset of solutions) could be identified as clearly superior to the remaining solutions. Grid sensitivity studies presented by multiple BANC-III participants demonstrated a relatively consistent trend of reduced surface pressure fluctuations, higher levels of turbulent kinetic energy in the flow, and lower levels of both narrow band peaks and the broadband component of unsteady pressure spectra in the nearfield and farfield. The lessons learned from the BANC-III contributions have been used to identify improvements to the problem statement for future Category-7 investigations.

  1. Prediction of helicopter rotor noise in hover

    NASA Astrophysics Data System (ADS)

    Kusyumov, A. N.; Mikhailov, S. A.; Garipova, L. I.; Batrakov, A. S.; Barakos, G.

    2015-05-01

    Two mathematical models are used in this work to estimate the acoustics of a hovering main rotor. The first model is based on the Ffowcs Williams-Howkings equations using the formulation of Farassat. An analytical approach is followed for this model, to determine the thickness and load noise contributions of the rotor blade in hover. The second approach allows using URANS and RANS CFD solutions and based on numerical solution of the Ffowcs Williams-Howkings equations. The employed test cases correspond to a model rotor available at the KNRTUKAI aerodynamics laboratory. The laboratory is equipped with a system of acoustic measurements, and comparisons between predictions and measurements are to be attempted as part of this work.

  2. Urban daytime traffic noise prediction models.

    PubMed

    da Paz, Elaine Carvalho; Zannin, Paulo Henrique Trombetta

    2010-04-01

    An evaluation was made of the acoustic environment generated by an urban highway using in situ measurements. Based on the data collected, a mathematical model was designed for the main sound levels (L (eq), L (10), L (50), and L (90)) as a function of the correlation between sound levels and between the equivalent sound pressure level and traffic variables. Four valid groups of mathematical models were generated to calculate daytime sound levels, which were statistically validated. It was found that the new models can be considered as accurate as other models presented in the literature to assess and predict daytime traffic noise, and that they stand out and differ from the existing models described in the literature thanks to two characteristics, namely, their linearity and the application of class intervals.

  3. Variability in the Propagation Phase of CFD-Based Noise Prediction: Summary of Results From Category 8 of the BANC-III Workshop

    NASA Technical Reports Server (NTRS)

    Lopes, Leonard; Redonnet, Stephane; Imamura, Taro; Ikeda, Tomoaki; Zawodny, Nikolas; Cunha, Guilherme

    2015-01-01

    The usage of Computational Fluid Dynamics (CFD) in noise prediction typically has been a two part process: accurately predicting the flow conditions in the near-field and then propagating the noise from the near-field to the observer. Due to the increase in computing power and the cost benefit when weighed against wind tunnel testing, the usage of CFD to estimate the local flow field of complex geometrical structures has become more routine. Recently, the Benchmark problems in Airframe Noise Computation (BANC) workshops have provided a community focus on accurately simulating the local flow field near the body with various CFD approaches. However, to date, little effort has been given into assessing the impact of the propagation phase of noise prediction. This paper includes results from the BANC-III workshop which explores variability in the propagation phase of CFD-based noise prediction. This includes two test cases: an analytical solution of a quadrupole source near a sphere and a computational solution around a nose landing gear. Agreement between three codes was very good for the analytic test case, but CFD-based noise predictions indicate that the propagation phase can introduce 3dB or more of variability in noise predictions.

  4. Helicopter noise prediction - The current status and future direction

    NASA Technical Reports Server (NTRS)

    Brentner, Kenneth S.; Farassat, F.

    1992-01-01

    The paper takes stock of the progress, assesses the current prediction capabilities, and forecasts the direction of future helicopter noise prediction research. The acoustic analogy approach, specifically, theories based on the Ffowcs Williams-Hawkings equations, are the most widely used for deterministic noise sources. Thickness and loading noise can be routinely predicted given good plane motion and blade loading inputs. Blade-vortex interaction noise can also be predicted well with measured input data, but prediction of airloads with the high spatial and temporal resolution required for BVI is still difficult. Current semiempirical broadband noise predictions are useful and reasonably accurate. New prediction methods based on a Kirchhoff formula and direct computation appear to be very promising, but are currently very demanding computationally.

  5. Supersonic Jet Noise Reductions Predicted with Increased Jet Spreading Rate

    NASA Technical Reports Server (NTRS)

    Dahl, Milo D.; Morris, Philip J.

    1995-01-01

    In this paper, predictions are made of noise radiation from single, supersonic, axisymmetric jets. We examine the effects of changes in operating conditions and the effects of simulated enhanced mixing that would increase the spreading rate of the jet shear layer on radiated noise levels. The radiated noise in the downstream direction is dominated by mixing noise and it is well described by the instability wave noise radiation analysis. A numerical prediction scheme is used for the mean flow providing an efficient method to obtain the mean flow development for various operating conditions and to simulate the enhanced mixing. Using far field radiated noise measurements as a reference, the calculations predict that enhanced jet spreading results in a reduction of radiated noise.

  6. Limits on the prediction of helicopter rotor noise using thickness and loading sources: Validation of helicopter noise prediction techniques

    NASA Technical Reports Server (NTRS)

    Succi, G. P.

    1983-01-01

    The techniques of helicopter rotor noise prediction attempt to describe precisely the details of the noise field and remove the empiricisms and restrictions inherent in previous methods. These techniques require detailed inputs of the rotor geometry, operating conditions, and blade surface pressure distribution. The Farassat noise prediction techniques was studied, and high speed helicopter noise prediction using more detailed representations of the thickness and loading noise sources was investigated. These predictions were based on the measured blade surface pressures on an AH-1G rotor and compared to the measured sound field. Although refinements in the representation of the thickness and loading noise sources improve the calculation, there are still discrepancies between the measured and predicted sound field. Analysis of the blade surface pressure data indicates shocks on the blades, which are probably responsible for these discrepancies.

  7. Numerical methods for engine-airframe integration

    SciTech Connect

    Murthy, S.N.B.; Paynter, G.C.

    1986-01-01

    Various papers on numerical methods for engine-airframe integration are presented. The individual topics considered include: scientific computing environment for the 1980s, overview of prediction of complex turbulent flows, numerical solutions of the compressible Navier-Stokes equations, elements of computational engine/airframe integrations, computational requirements for efficient engine installation, application of CAE and CFD techniques to complete tactical missile design, CFD applications to engine/airframe integration, and application of a second-generation low-order panel methods to powerplant installation studies. Also addressed are: three-dimensional flow analysis of turboprop inlet and nacelle configurations, application of computational methods to the design of large turbofan engine nacelles, comparison of full potential and Euler solution algorithms for aeropropulsive flow field computations, subsonic/transonic, supersonic nozzle flows and nozzle integration, subsonic/transonic prediction capabilities for nozzle/afterbody configurations, three-dimensional viscous design methodology of supersonic inlet systems for advanced technology aircraft, and a user's technology assessment.

  8. Broadband Noise Prediction When Turbulence Simulation Is Available - Derivation of Formulation 2B and Its Statistical Analysis

    NASA Technical Reports Server (NTRS)

    Farassat, Fereidoun; Casper, Jay H.

    2012-01-01

    We show that a simple modification of Formulation 1 of Farassat results in a new analytic expression that is highly suitable for broadband noise prediction when extensive turbulence simulation is available. This result satisfies all the stringent requirements, such as permitting the use of the exact geometry and kinematics of the moving body, that we have set as our goal in the derivation of useful acoustic formulas for the prediction of rotating blade and airframe noise. We also derive a simple analytic expression for the autocorrelation of the acoustic pressure that is valid in the near and far fields. Our analysis is based on the time integral of the acoustic pressure that can easily be obtained at any resolution for any observer time interval and digitally analyzed for broadband noise prediction. We have named this result as Formulation 2B of Farassat. One significant consequence of Formulation 2B is the derivation of the acoustic velocity potential for the thickness and loading terms of the Ffowcs Williams-Hawkings (FW-H) equation. This will greatly enhance the usefulness of the Fast Scattering Code (FSC) by providing a high fidelity boundary condition input for scattering predictions.

  9. Contra-Rotating Open Rotor Tone Noise Prediction

    NASA Technical Reports Server (NTRS)

    Envia, Edmane

    2014-01-01

    Reliable prediction of contra-rotating open rotor (CROR) noise is an essential element of any strategy for the development of low-noise open rotor propulsion systems that can meet both the community noise regulations and the cabin noise limits. Since CROR noise spectra typically exhibits a preponderance of tones, significant efforts have been directed towards predicting their tone spectra. To that end, there has been an ongoing effort at NASA to assess various in-house open rotor tone noise prediction tools using a benchmark CROR blade set for which significant aerodynamic and acoustic data had been acquired in wind tunnel tests. In the work presented here, the focus is on the near-field noise of the benchmark open rotor blade set at the cruise condition. Using an analytical CROR tone noise model with input from high-fidelity aerodynamic simulations, detailed tone noise spectral predictions have been generated and compared with the experimental data. Comparisons indicate that the theoretical predictions are in good agreement with the data, especially for the dominant CROR tones and their overall sound pressure level. The results also indicate that, whereas individual rotor tones are well predicted by the linear sources (i.e., thickness and loading), for the interaction tones it is essential that the quadrupole sources be included in the analysis.

  10. Contra-Rotating Open Rotor Tone Noise Prediction

    NASA Technical Reports Server (NTRS)

    Envia, Edmane

    2014-01-01

    Reliable prediction of contra-rotating open rotor (CROR) noise is an essential element of any strategy for the development of low-noise open rotor propulsion systems that can meet both the community noise regulations and cabin noise limits. Since CROR noise spectra exhibit a preponderance of tones, significant efforts have been directed towards predicting their tone content. To that end, there has been an ongoing effort at NASA to assess various in-house open rotor tone noise prediction tools using a benchmark CROR blade set for which significant aerodynamic and acoustic data have been acquired in wind tunnel tests. In the work presented here, the focus is on the nearfield noise of the benchmark open rotor blade set at the cruise condition. Using an analytical CROR tone noise model with input from high-fidelity aerodynamic simulations, tone noise spectra have been predicted and compared with the experimental data. Comparisons indicate that the theoretical predictions are in good agreement with the data, especially for the dominant tones and for the overall sound pressure level of tones. The results also indicate that, whereas the individual rotor tones are well predicted by the combination of the thickness and loading sources, for the interaction tones it is essential that the quadrupole source is also included in the analysis.

  11. Noise predictions of a high bypass turbofan engine using the Lockheed Near-Field Noise Prediction Program

    NASA Technical Reports Server (NTRS)

    Rawls, J. W., Jr.

    1986-01-01

    The prediction of engine noise during cruise using the Near-Field Noise Prediction Program developed by Lockheed is examined. Test conditions were established which simulate the operation of a high bypass turbofan engine under a wide range of operating conditions. These test conditions include variations in altitude, flight Mach number and thrust setting. Based on the results of noise prediction made using the Lockheed program, an evaluation of the impact of these test conditions on the overall sound pressure level(OASPL)and the one-third octave band spectra is made. An evaluation of the sensitivity of flight condition parameters is also made. The primary noise source from a high bypass turbofan was determined to be fan broadband shock noise. This noise source can be expected to be present during normal cruising conditions. When present, fan broadband shock noise usually dominates at all frequencies and all directivity angles. Other noise sources of importance are broadband shock noise from the primary jet, fan noise, fan mixing noise and turbine noise.

  12. Noise predictions of a high bypass turbofan engine using the Lockheed Near-Field Noise Prediction Program

    NASA Astrophysics Data System (ADS)

    Rawls, J. W., Jr.

    1986-07-01

    The prediction of engine noise during cruise using the Near-Field Noise Prediction Program developed by Lockheed is examined. Test conditions were established which simulate the operation of a high bypass turbofan engine under a wide range of operating conditions. These test conditions include variations in altitude, flight Mach number and thrust setting. Based on the results of noise prediction made using the Lockheed program, an evaluation of the impact of these test conditions on the overall sound pressure level(OASPL)and the one-third octave band spectra is made. An evaluation of the sensitivity of flight condition parameters is also made. The primary noise source from a high bypass turbofan was determined to be fan broadband shock noise. This noise source can be expected to be present during normal cruising conditions. When present, fan broadband shock noise usually dominates at all frequencies and all directivity angles. Other noise sources of importance are broadband shock noise from the primary jet, fan noise, fan mixing noise and turbine noise.

  13. Integrated airframe propulsion control

    NASA Technical Reports Server (NTRS)

    Fennell, R. E.; Black, S. B.

    1982-01-01

    Perturbation equations which describe flight dynamics and engine operation about a given operating point are combined to form an integrated aircraft/propulsion system model. Included in the model are the dependence of aerodynamic coefficients upon atmospheric variables along with the dependence of engine variables upon flight condition and inlet performance. An off-design engine performance model is used to identify interaction parameters in the model. Inclusion of subsystem interaction effects introduces coupling between flight and propulsion variables. To analyze interaction effects on control, consideration is first given to control requirements for separate flight and engine models. For the separate airframe model, feedback control provides substantial improvement in short period damping. For the integrated system, feedback control compensates for the coupling present in the model and provides good overall system stability. However, this feedback control law involves many non-zero gains. Analysis of suboptimal control strategies indicates that performance of the closed loop integrated system can be maintained with a feedback matrix in which the number of non-zero gains is small relative to the number of components in the feedback matrix.

  14. Modular Engine Noise Component Prediction System (MCP) Technical Description and Assessment Document

    NASA Technical Reports Server (NTRS)

    Herkes, William H.; Reed, David H.

    2005-01-01

    This report describes an empirical prediction procedure for turbofan engine noise. The procedure generates predicted noise levels for several noise components, including inlet- and aft-radiated fan noise, and jet-mixing noise. This report discusses the noise source mechanisms, the development of the prediction procedures, and the assessment of the accuracy of these predictions. Finally, some recommendations for future work are presented.

  15. Application of indoor noise prediction in the real world

    NASA Astrophysics Data System (ADS)

    Lewis, David N.

    2002-11-01

    Predicting indoor noise in industrial workrooms is an important part of the process of designing industrial plants. Predicted levels are used in the design process to determine compliance with occupational-noise regulations, and to estimate levels inside the walls in order to predict community noise radiated from the building. Once predicted levels are known, noise-control strategies can be developed. In this paper an overview of over 20 years of experience is given with the use of various prediction approaches to manage noise in Unilever plants. This work has applied empirical and ray-tracing approaches separately, and in combination, to design various packaging and production plants and other facilities. The advantages of prediction methods in general, and of the various approaches in particular, will be discussed. A case-study application of prediction methods to the optimization of noise-control measures in a food-packaging plant will be presented. Plans to acquire a simplified prediction model for use as a company noise-screening tool will be discussed.

  16. New Tool Released for Engine-Airframe Blade-Out Structural Simulations

    NASA Technical Reports Server (NTRS)

    Lawrence, Charles

    2004-01-01

    Researchers at the NASA Glenn Research Center have enhanced a general-purpose finite element code, NASTRAN, for engine-airframe structural simulations during steady-state and transient operating conditions. For steady-state simulations, the code can predict critical operating speeds, natural modes of vibration, and forced response (e.g., cabin noise and component fatigue). The code can be used to perform static analysis to predict engine-airframe response and component stresses due to maneuver loads. For transient response, the simulation code can be used to predict response due to bladeoff events and subsequent engine shutdown and windmilling conditions. In addition, the code can be used as a pretest analysis tool to predict the results of the bladeout test required for FAA certification of new and derivative aircraft engines. Before the present analysis code was developed, all the major aircraft engine and airframe manufacturers in the United States and overseas were performing similar types of analyses to ensure the structural integrity of engine-airframe systems. Although there were many similarities among the analysis procedures, each manufacturer was developing and maintaining its own structural analysis capabilities independently. This situation led to high software development and maintenance costs, complications with manufacturers exchanging models and results, and limitations in predicting the structural response to the desired degree of accuracy. An industry-NASA team was formed to overcome these problems by developing a common analysis tool that would satisfy all the structural analysis needs of the industry and that would be available and supported by a commercial software vendor so that the team members would be relieved of maintenance and development responsibilities. Input from all the team members was used to ensure that everyone's requirements were satisfied and that the best technology was incorporated into the code. Furthermore, because the code

  17. Prediction of Acoustic Noise in Switched Reluctance Motor Drives

    SciTech Connect

    Lin, CJ; Fahimi, B

    2014-03-01

    Prediction of acoustic noise distribution generated by electric machines has become an integral part of design and control in noise sensitive applications. This paper presents a fast and precise acoustic noise imaging technique for switched reluctance machines (SRMs). This method is based on distribution of radial vibration in the stator frame of the SRM. Radial vibration of the stator frame, at a network of probing points, is computed using input phase current and phase voltage waveforms. Sequentially, the acceleration of the probing network will be expanded to predict full acceleration on the stator frame surface, using which acoustic noise emission caused by the stator can be calculated using the boundary element method.

  18. A practical approach to helicopter internal noise prediction

    NASA Technical Reports Server (NTRS)

    Levine, L. S.; Defelice, J. J.

    1978-01-01

    A practical and well correlated procedure for predicting helicopter internal noise is presented. It accounts for the propagation of noise along multiple paths on an octave by octave basis. The method is sufficiently general to be applicable to conventional helicopters as well as other aircraft types, when the appropriate structural geometry, noise source strengths, and material acoustic properties are defined. A guide is provided for the prediction of various helicopter noise sources over a wide range of horsepower for use when measured data are not available. The method is applied to the prediction of the interior levels of the Civil Helicopter Research Aircraft (CHRA), both with and without soundproofing installed. Results include good correlation with measured levels and prediction of the speech interference level within 1.5 db at all conditions. A sample problem is also shown illustrating the use of the procedure. This example calculates the engine casing noise observed in the passenger cabin of the CHRA.

  19. Experimental validation of boundary element methods for noise prediction

    NASA Technical Reports Server (NTRS)

    Seybert, A. F.; Oswald, Fred B.

    1992-01-01

    Experimental validation of methods to predict radiated noise is presented. A combined finite element and boundary element model was used to predict the vibration and noise of a rectangular box excited by a mechanical shaker. The predicted noise was compared to sound power measured by the acoustic intensity method. Inaccuracies in the finite element model shifted the resonance frequencies by about 5 percent. The predicted and measured sound power levels agree within about 2.5 dB. In a second experiment, measured vibration data was used with a boundary element model to predict noise radiation from the top of an operating gearbox. The predicted and measured sound power for the gearbox agree within about 3 dB.

  20. Modular Engine Noise Component Prediction System (MCP) Program Users' Guide

    NASA Technical Reports Server (NTRS)

    Golub, Robert A. (Technical Monitor); Herkes, William H.; Reed, David H.

    2004-01-01

    This is a user's manual for Modular Engine Noise Component Prediction System (MCP). This computer code allows the user to predict turbofan engine noise estimates. The program is based on an empirical procedure that has evolved over many years at The Boeing Company. The data used to develop the procedure include both full-scale engine data and small-scale model data, and include testing done by Boeing, by the engine manufacturers, and by NASA. In order to generate a noise estimate, the user specifies the appropriate engine properties (including both geometry and performance parameters), the microphone locations, the atmospheric conditions, and certain data processing options. The version of the program described here allows the user to predict three components: inlet-radiated fan noise, aft-radiated fan noise, and jet noise. MCP predicts one-third octave band noise levels over the frequency range of 50 to 10,000 Hertz. It also calculates overall sound pressure levels and certain subjective noise metrics (e.g., perceived noise levels).

  1. Open Rotor Aeroacoustic Installation Effects for Conventional and Unconventional Airframes

    NASA Technical Reports Server (NTRS)

    Czech, Michael J.; Thomas, Russell H.

    2013-01-01

    As extensive experimental campaign was performed to study the aeroacoustic installation effects of an open rotor with respect to both a conventional tube and wing type airframe and an unconventional hybrid wing body airframe. The open rotor rig had two counter rotating rows of blades each with eight blades of a design originally flight tested in the 1980s. The aeroacoustic installation effects measured in an aeroacoustic wind tunnel included those from flow effects due to inflow distortion or wake interaction and acoustic propagation effects such as shielding and reflection. The objective of the test campaign was to quantify the installation effects for a wide range of parameters and configurations derived from the two airframe types. For the conventional airframe, the open rotor was positioned in increments in front of and then over the main wing and then in positions representative of tail mounted aircraft with a conventional tail, a T-tail and a U-tail. The interaction of the wake of the open rotor as well as acoustic scattering results in an increase of about 10 dB when the rotor is positioned in front of the main wing. When positioned over the main wing a substantial amount of noise reduction is obtained and this is also observed for tail-mounted installations with a large U-tail. For the hybrid wing body airframe, the open rotor was positioned over the airframe along the centerline as well as off-center representing a twin engine location. A primary result was the documentation of the noise reduction from shielding as a function of the location of the open rotor upstream of the trailing edge of the hybrid wing body. The effects from vertical surfaces and elevon deflection were also measured. Acoustic lining was specially designed and inserted flush with the elevon and airframe surface, the result was an additional reduction in open rotor noise propagating to the far field microphones. Even with the older blade design used, the experiment provided

  2. High Speed Jet Noise Prediction Using Large Eddy Simulation

    NASA Technical Reports Server (NTRS)

    Lele, Sanjiva K.

    2002-01-01

    Current methods for predicting the noise of high speed jets are largely empirical. These empirical methods are based on the jet noise data gathered by varying primarily the jet flow speed, and jet temperature for a fixed nozzle geometry. Efforts have been made to correlate the noise data of co-annular (multi-stream) jets and for the changes associated with the forward flight within these empirical correlations. But ultimately these emipirical methods fail to provide suitable guidance in the selection of new, low-noise nozzle designs. This motivates the development of a new class of prediction methods which are based on computational simulations, in an attempt to remove the empiricism of the present day noise predictions.

  3. Aircraft cabin noise prediction and optimization

    NASA Technical Reports Server (NTRS)

    Vaicaitis, R.

    1985-01-01

    Theoretical and experimental studies were conducted to determine the noise transmission into acoustic enclosures ranging from simple rectangular box models to full scale light aircraft in flight. The structural models include simple, stiffened, curved stiffened, and orthotropic panels and double wall windows. The theoretical solutions were obtained by model analysis. Transfer matrix and finite element procedures were utilized. Good agreement between theory and experiment has been achieved. An efficient acoustic add-on treatment was developed for interior noise control in a twin engine light aircraft.

  4. Sound quality prediction for engine-radiated noise

    NASA Astrophysics Data System (ADS)

    Liu, Hai; Zhang, Junhong; Guo, Peng; Bi, Fengrong; Yu, Hanzhengnan; Ni, Guangjian

    2015-05-01

    Diesel engine-radiated noise quality prediction is an important topic because engine noise has a significant impact on the overall vehicle noise. Sound quality prediction is based on subjective and objective evaluation of engine noise. The integrated satisfaction index (ISI) is proposed as a criterion for differentiate noise quality in the subjective evaluation, and five psychoacoustic parameters are selected for characterizing and analyzing the noise quality of the diesel engine objectively. The combination of support vector machines (SVM) and genetic algorithm (GA) is proposed in order to establish a model for predicting the diesel engine-radiated noise quality for all operation conditions. The performance of the GA-SVM model is compared with the BP neural network model, and the results show that the mean relative error of the GA-SVM model is smaller than the BP neural network model. The importance rank of the sound quality metrics to the ISI is indicated by the non-parametric correlation analysis. This study suggests that the GA-SVM model is very useful for accurately predicting the diesel engine-radiated noise quality.

  5. Advanced propeller noise prediction in the time domain

    NASA Technical Reports Server (NTRS)

    Farassat, F.; Dunn, M. H.; Spence, P. L.

    1992-01-01

    The time domain code ASSPIN gives acousticians a powerful technique of advanced propeller noise prediction. Except for nonlinear effects, the code uses exact solutions of the Ffowcs Williams-Hawkings equation with exact blade geometry and kinematics. By including nonaxial inflow, periodic loading noise, and adaptive time steps to accelerate computer execution, the development of this code becomes complete.

  6. A survey of the broadband shock associated noise prediction methods

    NASA Technical Reports Server (NTRS)

    Kim, Chan M.; Krejsa, Eugene A.; Khavaran, Abbas

    1992-01-01

    Several different prediction methods to estimate the broadband shock associated noise of a supersonic jet are introduced and compared with experimental data at various test conditions. The nozzle geometries considered for comparison include a convergent and a convergent-divergent nozzle, both axisymmetric. Capabilities and limitations of prediction methods in incorporating the two nozzle geometries, flight effect, and temperature effect are discussed. Predicted noise field shows the best agreement for a convergent nozzle geometry under static conditions. Predicted results for nozzles in flight show larger discrepancies from data and more dependable flight data are required for further comparison. Qualitative effects of jet temperature, as observed in experiment, are reproduced in predicted results.

  7. Investigation of Acoustical Shielding by a Wedge-Shaped Airframe

    NASA Technical Reports Server (NTRS)

    Gerhold, Carl H.; Clark, Lorenzo R.; Dunn, Mark H.; Tweed, John

    2004-01-01

    Experiments on a scale model of an advanced unconventional subsonic transport concept, the Blended Wing Body (BWB), have demonstrated significant shielding of inlet-radiated noise. A computational model of the shielding mechanism has been developed using a combination of boundary integral equation method (BIEM) and equivalent source method (ESM). The computation models the incident sound from a point source in a nacelle and determines the scattered sound field. In this way the sound fields with and without the airfoil can be estimated for comparison to experiment. An experimental test bed using a simplified wedge-shape airfoil and a broadband point noise source in a simulated nacelle has been developed for the purposes of verifying the analytical model and also to study the effect of engine nacelle placement on shielding. The experimental study is conducted in the Anechoic Noise Research Facility at NASA Langley Research Center. The analytic and experimental results are compared at 6300 and 8000 Hz. These frequencies correspond to approximately 150 Hz on the full scale aircraft. Comparison between the experimental and analytic results is quite good, not only for the noise scattering by the airframe, but also for the total sound pressure in the far field. Many of the details of the sound field that the analytic model predicts are seen or indicated in the experiment, within the spatial resolution limitations of the experiment. Changing nacelle location produces comparable changes in noise shielding contours evaluated analytically and experimentally. Future work in the project will be enhancement of the analytic model to extend the analysis to higher frequencies corresponding to the blade passage frequency of the high bypass ratio ducted fan engines that are expected to power the BWB.

  8. Investigation of Acoustical Shielding by a Wedge-Shaped Airframe

    NASA Technical Reports Server (NTRS)

    Gerhold, Carl H.; Clark, Lorenzo R.; Dunn, Mark H.; Tweed, John

    2006-01-01

    Experiments on a scale model of an advanced unconventional subsonic transport concept, the Blended Wing Body (BWB), have demonstrated significant shielding of inlet-radiated noise. A computational model of the shielding mechanism has been developed using a combination of boundary integral equation method (BIEM) and equivalent source method (ESM). The computation models the incident sound from a point source in a nacelle and determines the scattered sound field. In this way the sound fields with and without the airfoil can be estimated for comparison to experiment. An experimental test bed using a simplified wedge-shape airfoil and a broadband point noise source in a simulated nacelle has been developed for the purposes of verifying the analytical model and also to study the effect of engine nacelle placement on shielding. The experimental study is conducted in the Anechoic Noise Research Facility at NASA Langley Research Center. The analytic and experimental results are compared at 6300 and 8000 Hz. These frequencies correspond to approximately 150 Hz on the full scale aircraft. Comparison between the experimental and analytic results is quite good, not only for the noise scattering by the airframe, but also for the total sound pressure in the far field. Many of the details of the sound field that the analytic model predicts are seen or indicated in the experiment, within the spatial resolution limitations of the experiment. Changing nacelle location produces comparable changes in noise shielding contours evaluated analytically and experimentally. Future work in the project will be enhancement of the analytic model to extend the analysis to higher frequencies corresponding to the blade passage frequency of the high bypass ratio ducted fan engines that are expected to power the BWB.

  9. Study on noise prediction model and control schemes for substation.

    PubMed

    Chen, Chuanmin; Gao, Yang; Liu, Songtao

    2014-01-01

    With the government's emphasis on environmental issues of power transmission and transformation project, noise pollution has become a prominent problem now. The noise from the working transformer, reactor, and other electrical equipment in the substation will bring negative effect to the ambient environment. This paper focuses on using acoustic software for the simulation and calculation method to control substation noise. According to the characteristics of the substation noise and the techniques of noise reduction, a substation's acoustic field model was established with the SoundPLAN software to predict the scope of substation noise. On this basis, 4 reasonable noise control schemes were advanced to provide some helpful references for noise control during the new substation's design and construction process. And the feasibility and application effect of these control schemes can be verified by using the method of simulation modeling. The simulation results show that the substation always has the problem of excessive noise at boundary under the conventional measures. The excess noise can be efficiently reduced by taking the corresponding noise reduction methods. PMID:24672356

  10. Study on noise prediction model and control schemes for substation.

    PubMed

    Chen, Chuanmin; Gao, Yang; Liu, Songtao

    2014-01-01

    With the government's emphasis on environmental issues of power transmission and transformation project, noise pollution has become a prominent problem now. The noise from the working transformer, reactor, and other electrical equipment in the substation will bring negative effect to the ambient environment. This paper focuses on using acoustic software for the simulation and calculation method to control substation noise. According to the characteristics of the substation noise and the techniques of noise reduction, a substation's acoustic field model was established with the SoundPLAN software to predict the scope of substation noise. On this basis, 4 reasonable noise control schemes were advanced to provide some helpful references for noise control during the new substation's design and construction process. And the feasibility and application effect of these control schemes can be verified by using the method of simulation modeling. The simulation results show that the substation always has the problem of excessive noise at boundary under the conventional measures. The excess noise can be efficiently reduced by taking the corresponding noise reduction methods.

  11. Efficient Modelling and Prediction of Meshing Noise from Chain Drives

    NASA Astrophysics Data System (ADS)

    ZHENG, H.; WANG, Y. Y.; LIU, G. R.; LAM, K. Y.; QUEK, K. P.; ITO, T.; NOGUCHI, Y.

    2001-08-01

    This paper presents a practical approach for predicting the meshing noise due to the impact of chain rollers against the sprocket of chain drives. An acoustical model relating dynamic response of rollers and its induced sound pressure is developed based on the fact that the acoustic field is mainly created by oscillating rigid cylindrical rollers. Finite element techniques and numerical software codes are employed to model and simulate the acceleration response of each chain roller which is necessary for noise level prediction of a chain drive under varying operation conditions and different sprocket configurations. The predicted acoustic pressure levels of meshing noise are compared with the available experimental measurements. It is shown that the predictions are in reasonable agreement with the experiments and the approach enables designers to obtain required information on the noise level of a selected chain drive in a time- and cost-efficient manner.

  12. Jet Measurements for Development of Jet Noise Prediction Tools

    NASA Technical Reports Server (NTRS)

    Bridges, James E.

    2006-01-01

    The primary focus of my presentation is the development of the jet noise prediction code JeNo with most examples coming from the experimental work that drove the theoretical development and validation. JeNo is a statistical jet noise prediction code, based upon the Lilley acoustic analogy. Our approach uses time-average 2-D or 3-D mean and turbulent statistics of the flow as input. The output is source distributions and spectral directivity.

  13. Measurement, analysis, and prediction of aircraft interior noise

    NASA Technical Reports Server (NTRS)

    Howlett, J. T.; Williams, L. H.; Catherines, J. J.; Jha, S. K.

    1976-01-01

    Considerations of comfort of passengers and crew in light aircraft and helicopters indicate substantial benefits may be obtained by the reduction of interior noise levels. This paper discusses an ongoing research effort to reduce interior noise in such vehicles. Data from both field and laboratory studies for a light aircraft are presented. The laboratory data indicate that structural vibration is an efficient source of interior noise and should be considered in the reduction of interior noise. Flight data taken on a helicopter before and after installation of acoustic treatment demonstrate that over 30 dB of noise reduction can be obtained in certain portions of the spectra. However, subjective evaluations of the treated vehicle indicate that further reductions in interior noise are desirable. An existing interior noise prediction method which was developed for large jet transports was applied to study low-frequency noise in a light aircraft fuselage. The results indicate that improvements in the analytical model may be necessary for the prediction of interior noise of light aircraft.

  14. Initial Integration of Noise Prediction Tools for Acoustic Scattering Effects

    NASA Technical Reports Server (NTRS)

    Nark, Douglas M.; Burley, Casey L.; Tinetti, Ana; Rawls, John W.

    2008-01-01

    This effort provides an initial glimpse at NASA capabilities available in predicting the scattering of fan noise from a non-conventional aircraft configuration. The Aircraft NOise Prediction Program, Fast Scattering Code, and the Rotorcraft Noise Model were coupled to provide increased fidelity models of scattering effects on engine fan noise sources. The integration of these codes led to the identification of several keys issues entailed in applying such multi-fidelity approaches. In particular, for prediction at noise certification points, the inclusion of distributed sources leads to complications with the source semi-sphere approach. Computational resource requirements limit the use of the higher fidelity scattering code to predict radiated sound pressure levels for full scale configurations at relevant frequencies. And, the ability to more accurately represent complex shielding surfaces in current lower fidelity models is necessary for general application to scattering predictions. This initial step in determining the potential benefits/costs of these new methods over the existing capabilities illustrates a number of the issues that must be addressed in the development of next generation aircraft system noise prediction tools.

  15. Broadband Noise Predictions for an Airfoil in a Turbulent Stream

    NASA Technical Reports Server (NTRS)

    Casper, J.; Farassat, F.; Mish, P. F.; Devenport, W. J.

    2003-01-01

    Loading noise is predicted from unsteady surface pressure measurements on a NACA 0015 airfoil immersed in grid-generated turbulence. The time-dependent pressure is obtained from an array of synchronized transducers on the airfoil surface. Far field noise is predicted by using the time-dependent surface pressure as input to Formulation 1A of Farassat, a solution of the Ffowcs Williams - Hawkings equation. Acoustic predictions are performed with and without the effects of airfoil surface curvature. Scaling rules are developed to compare the present far field predictions with acoustic measurements that are available in the literature.

  16. Broadband Noise Control Using Predictive Techniques

    NASA Technical Reports Server (NTRS)

    Eure, Kenneth W.; Juang, Jer-Nan

    1997-01-01

    Predictive controllers have found applications in a wide range of industrial processes. Two types of such controllers are generalized predictive control and deadbeat control. Recently, deadbeat control has been augmented to include an extended horizon. This modification, named deadbeat predictive control, retains the advantage of guaranteed stability and offers a novel way of control weighting. This paper presents an application of both predictive control techniques to vibration suppression of plate modes. Several system identification routines are presented. Both algorithms are outlined and shown to be useful in the suppression of plate vibrations. Experimental results are given and the algorithms are shown to be applicable to non- minimal phase systems.

  17. Broadband Trailing Edge Noise Predictions in the Time Domain. Revised

    NASA Technical Reports Server (NTRS)

    Casper, Jay; Farassat, Fereidoun

    2003-01-01

    A recently developed analytic result in acoustics, "Formulation 1B," is used to compute broadband trailing edge noise from an unsteady surface pressure distribution on a thin airfoil in the time domain. This formulation is a new solution of the Ffowcs Willliams-Hawkings equation with the loading source term, and has been shown in previous research to provide time domain predictions of broadband noise that are in excellent agreement with experimental results. Furthermore, this formulation lends itself readily to rotating reference frames and statistical analysis of broadband trailing edge noise. Formulation 1B is used to calculate the far field noise radiated from the trailing edge of a NACA 0012 airfoil in low Mach number flows, by using both analytical and experimental data on the airfoil surface. The acoustic predictions are compared with analytical results and experimental measurements that are available in the literature. Good agreement between predictions and measurements is obtained.

  18. Theoretical study and prediction of BVI noise including close interactions

    NASA Astrophysics Data System (ADS)

    Spiegel, Pierre; Rahier, Gilles

    1991-05-01

    The following study deals with the highly impulsive blade-vortex interaction (BVI) noise which is generated by helicopter main rotors in descent flight. Two computer codes have been especially designed to predict it at reduced computing costs, starting from given vortices. The aerodynamic code, called MAIR, predicts the unsteady airloads, even for head-on collisions, by using a singularity method and modeling the vortices as cloud vortices with viscous cores. The acoustic code, called PARIS, computes the resulting radiated loading noise and is based on the Ffowcs Williams and Hawkings equation. These two codes are ready to perform noise prediction in the flight cases but the vortex prediction required for input data still needs to be improved. While waiting for better wake data, the two codes have been used for a theoretical parametric study of arbitrary single blade-vortex interactions. This study gives a physical insight of the phenomenon and its predicted tendencies could help designing quieter blades.

  19. State of Jet Noise Prediction-NASA Perspective

    NASA Technical Reports Server (NTRS)

    Bridges, James E.

    2008-01-01

    This presentation covers work primarily done under the Airport Noise Technical Challenge portion of the Supersonics Project in the Fundamental Aeronautics Program. To provide motivation and context, the presentation starts with a brief overview of the Airport Noise Technical Challenge. It then covers the state of NASA s jet noise prediction tools in empirical, RANS-based, and time-resolved categories. The empirical tools, requires seconds to provide a prediction of noise spectral directivity with an accuracy of a few dB, but only for axisymmetric configurations. The RANS-based tools are able to discern the impact of three-dimensional features, but are currently deficient in predicting noise from heated jets and jets with high speed and require hours to produce their prediction. The time-resolved codes are capable of predicting resonances and other time-dependent phenomena, but are very immature, requiring months to deliver predictions without unknown accuracies and dependabilities. In toto, however, when one considers the progress being made it appears that aeroacoustic prediction tools are soon to approach the level of sophistication and accuracy of aerodynamic engineering tools.

  20. Measurements and Predictions of High Frequency Ambient Noise

    NASA Astrophysics Data System (ADS)

    Holden, Andrew

    2004-11-01

    A great deal has been published on ambient noise. Most of this has covered (a) omni directional levels, and (b) the vertical and horizontal directivity of shipping noise at low frequencies. There is some published material on the vertical directivity of wind generated noise at lower frequencies, but very little at higher frequencies. In order to study wind generated ambient noise at higher frequencies, work has recently started using a small planar array from QinetiQ Bincleaves. As well as measurements, a model called CANARY has been written to predict ambient noise vertical directivity and array responses to this noise. This paper contains some comparisons between CANARY predictions and (a) previous measured vertical directivity data at 4.5 kHz, (b) measured omni-directional data, and (c) initial analysis of the planar array measurements. The paper shows the nature of the ambient noise vertical structure at higher frequencies and that the CANARY predictions are in good agreement with the measurements.

  1. The Acoustic Analogy and Alternative Theories for Jet Noise Prediction

    NASA Technical Reports Server (NTRS)

    Morris, Philip J.; Farassat, F.

    2002-01-01

    This paper describes several methods for the prediction of jet noise. All but one of the noise prediction schemes are based on Lighthill's or Lilley's acoustic analogy while the other is the jet noise generation model recently proposed by Tam and Auriault. In all the approaches some assumptions must be made concerning the statistical properties of the turbulent sources. In each case the characteristic scales of the turbulence are obtained from a solution of the Reynolds-averaged Navier Stokes equation using a k - epsilon turbulence model. It is shown that, for the same level of empiricism, Tam and Auriault's model yields better agreement with experimental noise measurements than the acoustic analogy. It is then shown that this result is not because of some fundamental flaw in the acoustic analogy approach: but, is associated with the assumptions made in the approximation of the turbulent source statistics. If consistent assumptions are made, both the acoustic analogy and Tam and Auriault's model yield identical noise predictions. The paper concludes with a proposal for an acoustic analogy that provides a clearer identification of the equivalent source mechanisms and a discussion of noise prediction issues that remain to be resolved.

  2. The Acoustic Analogy and Alternative Theories for Jet Noise Prediction

    NASA Technical Reports Server (NTRS)

    Morris, Philip J.; Farassat, F.; Morris, Philip J.

    2002-01-01

    This paper describes several methods for the prediction of jet noise. All but one of the noise prediction schemes are based on Lighthill's or Lilley's acoustic analogy while the other is the jet noise generation model recently proposed by Tam and Auriault. In all the approaches some assumptions must be made concerning the statistical properties of the turbulent sources. In each case the characteristic scales of the turbulence are obtained from a solution of the Reynolds-averaged Navier Stokes equation using a k-epsilon turbulence model. It is shown that, for the same level of empiricism, Tam and Auriault's model yields better agreement with experimental noise measurements than the acoustic analogy. It is then shown that this result is not because of some fundamental flaw in the acoustic analogy approach: but, is associated with the assumptions made in the approximation of the turbulent source statistics. If consistent assumptions are made, both the acoustic analogy and Tam and Auriault's model yield identical noise predictions. The paper concludes with a proposal for an acoustic analogy that provides a clearer identification of the equivalent source mechanisms and a discussion of noise prediction issues that remain to be resolved.

  3. Acoustic Analogy and Alternative Theories for Jet Noise Prediction

    NASA Technical Reports Server (NTRS)

    Morris, Philip J.; Farassat, F.

    2002-01-01

    Several methods for the prediction of jet noise are described. All but one of the noise prediction schemes are based on Lighthill's or Lilley's acoustic analogy, whereas the other is the jet noise generation model recently proposed by Tam and Auriault. In all of the approaches, some assumptions must be made concerning the statistical properties of the turbulent sources. In each case the characteristic scales of the turbulence are obtained from a solution of the Reynolds-averaged Navier-Stokes equation using a kappa-sigma turbulence model. It is shown that, for the same level of empiricism, Tam and Auriault's model yields better agreement with experimental noise measurements than the acoustic analogy. It is then shown that this result is not because of some fundamental flaw in the acoustic analogy approach, but instead is associated with the assumptions made in the approximation of the turbulent source statistics. If consistent assumptions are made, both the acoustic analogy and Tam and Auriault's model yield identical noise predictions. In conclusion, a proposal is presented for an acoustic analogy that provides a clearer identification of the equivalent source mechanisms, as is a discussion of noise prediction issues that remain to be resolved.

  4. Trailing Edge Noise Prediction Based on a New Acoustic Formulation

    NASA Technical Reports Server (NTRS)

    Casper, J.; Farassat, F.

    2002-01-01

    A new analytic result in acoustics called 'Formulation 1B,' proposed by Farassat, is used to compute broadband trailing edge noise from an unsteady surface pressure distribution on a thin airfoil in the time domain. This formulation is a new solution of the Ffowcs Williams-Hawkings equation with the loading source term, and has been shown in previous research to provide time domain predictions of broadband noise that are in excellent agreement with experiment. Furthermore, this formulation lends itself readily to rotating reference frames and statistical analysis of broadband trailing edge noise. Formulation 1B is used to calculate the far field noise radiated from the trailing edge of a NACA 0012 airfoil in low Mach number flows, using both analytical and experimental data on the airfoil surface. The results are compared to analytical results and experimental measurements that are available in the literature. Good agreement between predictions and measurements is obtained.

  5. The NASA aircraft noise prediction program improved propeller analysis system

    NASA Technical Reports Server (NTRS)

    Nguyen, L. Cathy

    1991-01-01

    The improvements and the modifications of the NASA Aircraft Noise Prediction Program (ANOPP) and the Propeller Analysis System (PAS) are described. Comparisons of the predictions and the test data are included in the case studies for the flat plate model in the Boundary Layer Module, for the effects of applying compressibility corrections to the lift and pressure coefficients, for the use of different weight factors in the Propeller Performance Module, for the use of the improved retarded time equation solution, and for the effect of the number grids in the Transonic Propeller Noise Module. The DNW tunnel test data of a propeller at different angles of attack and the Dowty Rotol data are compared with ANOPP predictions. The effect of the number of grids on the Transonic Propeller Noise Module predictions and the comparison of ANOPP TPN and DFP-ATP codes are studied. In addition to the above impact studies, the transonic propeller noise predictions for the SR-7, the UDF front rotor, and the support of the enroute noise test program are included.

  6. Analytical developments for definition and prediction of USB noise

    NASA Technical Reports Server (NTRS)

    Reddy, N. N.; Tam, C. K. W.

    1976-01-01

    A systematic acoustic data base and associated flow data are used in identifying the noise generating mechanisms of upper surface blown flap configurations of short takeoff and landing aircraft. Theory is developed for the radiated sound field of the highly sheared flow of the trailing edge wake. An empirical method is also developed using extensive experimental data and physical reasonings to predict the noise levels.

  7. Program Predicts Broadband Noise from a Turbofan Engine

    NASA Technical Reports Server (NTRS)

    Morin, Bruce L.

    2004-01-01

    Broadband Fan Noise Prediction System (BFaNS) is a computer program that, as its name indicates, predicts the broadband noise generated by the fan stage of a turbofan engine. This noise is the sum of (1) turbulent-inflow noise, which is caused by turbulence impinging on leading edges of the fan and the fan exit guide vane and (2) self noise, which is caused by turbulence convecting past the corresponding trailing edges. The user provides input data on the fan-blade, vane, and flow-path geometries and on the mean and turbulent components of the flow field. BFaNS then calculates the turbulent-inflow noise by use of D. B. Hanson's theory, which relates sound power to the inflow turbulence characteristics and the cascade geometry. Hanson s program, BBCASCADE, is incorporated into BFaNS, wherein it is applied to the rotor and stator in a stripwise manner. The spectra of upstream and downstream sound powers radiated by each strip are summed to obtain the total upstream and downstream sound-power spectra. The self-noise contributions are calculated by S. A. L. Glegg's theory, which is also applied in a stripwise manner. The current version of BFaNS is limited to fans with subsonic tip speeds.

  8. Prediction and removal of rotation noise in airborne EM systems

    NASA Astrophysics Data System (ADS)

    Kratzer, Terence 12Macnae, James

    2014-03-01

    We aim to eliminate or reduce significant impediments to conductive target detection and conductive cover penetration in airborne electromagnetic (AEM) systems. Existing limitations come from the very high noise encountered at low base frequencies, caused by rotations of vector magnetic field sensors in the Earth's magnetic field. We use the output of tri-axial rotation-rate sensors to predict and subtract the rotation noise from rigidly coupled ARMIT magnetic field sensors. The approach is successful in reducing rotation noise by one to two orders of magnitude at low frequencies.

  9. Downwind rotor horizontal axis wind turbine noise prediction

    NASA Technical Reports Server (NTRS)

    Metzger, F. B.; Klatte, R. J.

    1981-01-01

    NASA and industry are currently cooperating in the conduct of extensive experimental and analytical studies to understand and predict the noise of large, horizontal axis wind turbines. This effort consists of (1) obtaining high quality noise data under well controlled and documented test conditions, (2) establishing the annoyance criteria for impulse noise of the type generated by horizontal axis wind turbines with rotors downwind of the support tower, (3) defining the wake characteristics downwind of the axial location of the plane of rotation, (4) comparing predictions with measurements made by use of wake data, and (5) comparing predictions with annoyance criteria. The status of work by Hamilton Standard in the above areas which was done in support of the cooperative NASA and industry studies is briefly summarized.

  10. Predicting perception in noise using cortical auditory evoked potentials.

    PubMed

    Billings, Curtis J; McMillan, Garnett P; Penman, Tina M; Gille, Sun Mi

    2013-12-01

    Speech perception in background noise is a common challenge across individuals and health conditions (e.g., hearing impairment, aging, etc.). Both behavioral and physiological measures have been used to understand the important factors that contribute to perception-in-noise abilities. The addition of a physiological measure provides additional information about signal-in-noise encoding in the auditory system and may be useful in clarifying some of the variability in perception-in-noise abilities across individuals. Fifteen young normal-hearing individuals were tested using both electrophysiology and behavioral methods as a means to determine (1) the effects of signal-to-noise ratio (SNR) and signal level and (2) how well cortical auditory evoked potentials (CAEPs) can predict perception in noise. Three correlation/regression approaches were used to determine how well CAEPs predicted behavior. Main effects of SNR were found for both electrophysiology and speech perception measures, while signal level effects were found generally only for speech testing. These results demonstrate that when signals are presented in noise, sensitivity to SNR cues obscures any encoding of signal level cues. Electrophysiology and behavioral measures were strongly correlated. The best physiological predictors (e.g., latency, amplitude, and area of CAEP waves) of behavior (SNR at which 50 % of the sentence is understood) were N1 latency and N1 amplitude measures. In addition, behavior was best predicted by the 70-dB signal/5-dB SNR CAEP condition. It will be important in future studies to determine the relationship of electrophysiology and behavior in populations who experience difficulty understanding speech in noise such as those with hearing impairment or age-related deficits.

  11. A Stochastic Simulation Framework for the Prediction of Strategic Noise Mapping and Occupational Noise Exposure Using the Random Walk Approach

    PubMed Central

    Haron, Zaiton; Bakar, Suhaimi Abu; Dimon, Mohamad Ngasri

    2015-01-01

    Strategic noise mapping provides important information for noise impact assessment and noise abatement. However, producing reliable strategic noise mapping in a dynamic, complex working environment is difficult. This study proposes the implementation of the random walk approach as a new stochastic technique to simulate noise mapping and to predict the noise exposure level in a workplace. A stochastic simulation framework and software, namely RW-eNMS, were developed to facilitate the random walk approach in noise mapping prediction. This framework considers the randomness and complexity of machinery operation and noise emission levels. Also, it assesses the impact of noise on the workers and the surrounding environment. For data validation, three case studies were conducted to check the accuracy of the prediction data and to determine the efficiency and effectiveness of this approach. The results showed high accuracy of prediction results together with a majority of absolute differences of less than 2 dBA; also, the predicted noise doses were mostly in the range of measurement. Therefore, the random walk approach was effective in dealing with environmental noises. It could predict strategic noise mapping to facilitate noise monitoring and noise control in the workplaces. PMID:25875019

  12. A stochastic simulation framework for the prediction of strategic noise mapping and occupational noise exposure using the random walk approach.

    PubMed

    Han, Lim Ming; Haron, Zaiton; Yahya, Khairulzan; Bakar, Suhaimi Abu; Dimon, Mohamad Ngasri

    2015-01-01

    Strategic noise mapping provides important information for noise impact assessment and noise abatement. However, producing reliable strategic noise mapping in a dynamic, complex working environment is difficult. This study proposes the implementation of the random walk approach as a new stochastic technique to simulate noise mapping and to predict the noise exposure level in a workplace. A stochastic simulation framework and software, namely RW-eNMS, were developed to facilitate the random walk approach in noise mapping prediction. This framework considers the randomness and complexity of machinery operation and noise emission levels. Also, it assesses the impact of noise on the workers and the surrounding environment. For data validation, three case studies were conducted to check the accuracy of the prediction data and to determine the efficiency and effectiveness of this approach. The results showed high accuracy of prediction results together with a majority of absolute differences of less than 2 dBA; also, the predicted noise doses were mostly in the range of measurement. Therefore, the random walk approach was effective in dealing with environmental noises. It could predict strategic noise mapping to facilitate noise monitoring and noise control in the workplaces.

  13. Predicting the asymmetric response of a genetic switch to noise.

    PubMed

    Ochab-Marcinek, Anna

    2008-09-01

    We present a simple analytical tool which gives an approximate insight into the stationary behavior of nonlinear systems undergoing the influence of a weak and rapid noise from one dominating source, e.g. the kinetic equations describing a genetic switch with the concentration of one substrate fluctuating around a constant mean. The proposed method allows for predicting the asymmetric response of the genetic switch to noise, arising from the noise-induced shift of stationary states. The method has been tested on an example model of the lac operon regulatory network: a reduced Yildirim-Mackey model with fluctuating extracellular lactose concentration. We calculate analytically the shift of the system's stationary states in the presence of noise. The results of the analytical calculation are in excellent agreement with the results of numerical simulation of the noisy system. The simulation results suggest that the structure of the kinetics of the underlying biochemical reactions protects the bistability of the lactose utilization mechanism from environmental fluctuations. We show that, in the consequence of the noise-induced shift of stationary states, the presence of fluctuations stabilizes the behavior of the system in a selective way: Although the extrinsic noise facilitates, to some extent, switching off the lactose metabolism, the same noise prevents it from switching on. PMID:18554612

  14. A review of propeller noise prediction methodology: 1919-1994

    NASA Technical Reports Server (NTRS)

    Metzger, F. Bruce

    1995-01-01

    This report summarizes a review of the literature regarding propeller noise prediction methods. The review is divided into six sections: (1) early methods; (2) more recent methods based on earlier theory; (3) more recent methods based on the Acoustic Analogy; (4) more recent methods based on Computational Acoustics; (5) empirical methods; and (6) broadband methods. The report concludes that there are a large number of noise prediction procedures available which vary markedly in complexity. Deficiencies in accuracy of methods in many cases may be related, not to the methods themselves, but the accuracy and detail of the aerodynamic inputs used to calculate noise. The steps recommended in the report to provide accurate and easy to use prediction methods are: (1) identify reliable test data; (2) define and conduct test programs to fill gaps in the existing data base; (3) identify the most promising prediction methods; (4) evaluate promising prediction methods relative to the data base; (5) identify and correct the weaknesses in the prediction methods, including lack of user friendliness, and include features now available only in research codes; (6) confirm the accuracy of improved prediction methods to the data base; and (7) make the methods widely available and provide training in their use.

  15. 23 CFR 772.17 - Traffic noise prediction.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... publications are incorporated by reference in accordance with 5 U.S.C. 552(a) and 1 CFR part 51 and are on file... Federal Highway Administration, 1200 New Jersey Avenue, SE., Washington, DC 20590, as provided in 49 CFR... 23 Highways 1 2011-04-01 2011-04-01 false Traffic noise prediction. 772.17 Section 772.17...

  16. NASTRAN application for the prediction of aircraft interior noise

    NASA Astrophysics Data System (ADS)

    Marulo, Francesco; Beyer, Todd B.

    1987-08-01

    The application of a structural-acoustic analogy within the NASTRAN finite element program for the prediction of aircraft interior noise is presented. Some refinements of the method, which reduce the amount of computation required for large, complex structures, are discussed. Also, further improvements are proposed and preliminary comparisons with structural and acoustic modal data obtained for a large, composite cylinder are presented.

  17. NASTRAN application for the prediction of aircraft interior noise

    NASA Technical Reports Server (NTRS)

    Marulo, Francesco; Beyer, Todd B.

    1987-01-01

    The application of a structural-acoustic analogy within the NASTRAN finite element program for the prediction of aircraft interior noise is presented. Some refinements of the method, which reduce the amount of computation required for large, complex structures, are discussed. Also, further improvements are proposed and preliminary comparisons with structural and acoustic modal data obtained for a large, composite cylinder are presented.

  18. 23 CFR 772.9 - Traffic noise prediction.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... title 1, CFR, and are on file at the National Archives and Record Administration (NARA). For information... 20590, as provided in part 7 of title 49, CFR. These documents are also available on the FHWA's Traffic...) Average pavement type shall be used in the FHWA TNM for future noise level prediction unless a...

  19. 23 CFR 772.9 - Traffic noise prediction.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... title 1, CFR, and are on file at the National Archives and Record Administration (NARA). For information... 20590, as provided in part 7 of title 49, CFR. These documents are also available on the FHWA's Traffic...) Average pavement type shall be used in the FHWA TNM for future noise level prediction unless a...

  20. 23 CFR 772.9 - Traffic noise prediction.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... title 1, CFR, and are on file at the National Archives and Record Administration (NARA). For information... 20590, as provided in part 7 of title 49, CFR. These documents are also available on the FHWA's Traffic...) Average pavement type shall be used in the FHWA TNM for future noise level prediction unless a...

  1. Heavy-tailed prediction error: a difficulty in predicting biomedical signals of 1/f noise type.

    PubMed

    Li, Ming; Zhao, Wei; Chen, Biao

    2012-01-01

    A fractal signal x(t) in biomedical engineering may be characterized by 1/f noise, that is, the power spectrum density (PSD) divergences at f = 0. According the Taqqu's law, 1/f noise has the properties of long-range dependence and heavy-tailed probability density function (PDF). The contribution of this paper is to exhibit that the prediction error of a biomedical signal of 1/f noise type is long-range dependent (LRD). Thus, it is heavy-tailed and of 1/f noise. Consequently, the variance of the prediction error is usually large or may not exist, making predicting biomedical signals of 1/f noise type difficult. PMID:23251226

  2. A formulation of rotor-airframe coupling for design analysis of vibrations of helicopter airframes

    NASA Technical Reports Server (NTRS)

    Kvaternik, R. G.; Walton, W. C., Jr.

    1982-01-01

    A linear formulation of rotor airframe coupling intended for vibration analysis in airframe structural design is presented. The airframe is represented by a finite element analysis model; the rotor is represented by a general set of linear differential equations with periodic coefficients; and the connections between the rotor and airframe are specified through general linear equations of constraint. Coupling equations are applied to the rotor and airframe equations to produce one set of linear differential equations governing vibrations of the combined rotor airframe system. These equations are solved by the harmonic balance method for the system steady state vibrations. A feature of the solution process is the representation of the airframe in terms of forced responses calculated at the rotor harmonics of interest. A method based on matrix partitioning is worked out for quick recalculations of vibrations in design studies when only relatively few airframe members are varied. All relations are presented in forms suitable for direct computer implementation.

  3. Predicting Noise From Aircraft Turbine-Engine Combustors

    NASA Technical Reports Server (NTRS)

    Gliebe, P.; Mani, R.; Salamah, S.; Coffin, R.; Mehta, Jayesh

    2005-01-01

    COMBUSTOR and CNOISE are computer codes that predict far-field noise that originates in the combustors of modern aircraft turbine engines -- especially modern, low-gaseous-emission engines, the combustors of which sometimes generate several decibels more noise than do the combustors of older turbine engines. COMBUSTOR implements an empirical model of combustor noise derived from correlations between engine-noise data and operational and geometric parameters, and was developed from databases of measurements of acoustic emissions of engines. CNOISE implements an analytical and computational model of the propagation of combustor temperature fluctuations (hot spots) through downstream turbine stages. Such hot spots are known to give rise to far-field noise. CNOISE is expected to be helpful in determining why low-emission combustors are sometimes noisier than older ones, to provide guidance for refining the empirical correlation model embodied in the COMBUSTOR code, and to provide insight on how to vary downstream turbinestage geometry to reduce the contribution of hot spots to far-field noise.

  4. Proceedings of the Airframe Icing Workshop

    NASA Technical Reports Server (NTRS)

    Colantonio, Ron O. (Editor)

    2009-01-01

    The NASA Glenn Research Center (GRC) has a long history of working with its partners towards the understanding of ice accretion formation and its associated degradation of aerodynamic performance. The June 9, 2009, Airframe Icing Workshop held at GRC provided an opportunity to examine the current NASA airframe icing research program and to dialogue on remaining and emerging airframe icing issues and research with the external community. Some of the airframe icing gaps identified included, but are not limited to, ice accretion simulation enhancements, three-dimensional benchmark icing database development, three-dimensional iced aerodynamics modeling, and technology development for a smart icing system.

  5. Measurement and prediction of Energy Efficient Engine noise

    NASA Technical Reports Server (NTRS)

    Lavin, S. P.; Ho, P. Y.; Chamberlin, R.

    1984-01-01

    The NASA/GE Energy Efficient Engine (E3) static noise levels were measured in an acoustic arena on the Integrated Core and Low Spool Test System. These measured levels were scaled to the appropriate size to power four study aircraft and were projected to flight for evaluation of noise levels relative to FAR36, Stage III limits. As a result of these evaluations, it is predicted that the NASA/GE E3 engine with a wide spacing cut-on blade/vane ratio fan and a forced mixer nozzle can meet FAR36 Stage III limits with sufficient design margin.

  6. Broadband Noise Predictions Based on a New Aeroacoustic Formulation

    NASA Technical Reports Server (NTRS)

    Casper, J.; Farassat, F.

    2002-01-01

    A new analytic result in acoustics called 'Formulation 1B,' proposed by Farassat, is used to compute the loading noise from an unsteady surface pressure distribution on a thin airfoil in the time domain. This formulation is a new solution of the Ffowcs Williams-Hawkings equation with the loading source term. The formulation contains a far-field surface integral that depends on the time derivative and the surface gradient of the pressure on the airfoil, as well as a contour integral on the boundary of the airfoil surface. As a first test case, the new formulation is used to compute the noise radiated from a flat plate, moving through a sinusoidal gust of constant frequency. The unsteady surface pressure for this test case is specified analytically from a result that is based on linear airfoil theory. This test case is used to examine the velocity scaling properties of Formulation 1B, and to demonstrate its equivalence to Formulation 1A, of Farassat. The new acoustic formulation, again with an analytic surface pressure, is then used to predict broadband noise radiated from an airfoil immersed in homogeneous turbulence. The results are compared with experimental data previously reported by Paterson and Amiet. Good agreement between predictions and measurements is obtained. The predicted results also agree very well with those of Paterson and Amiet, who used a frequency-domain approach. Finally, an alternative form of Formulation 1B is described for statistical analysis of broadband noise.

  7. Predicting speech intelligibility in noise for hearing-critical jobs

    NASA Astrophysics Data System (ADS)

    Soli, Sigfrid D.; Laroche, Chantal; Giguere, Christian

    2003-10-01

    Many jobs require auditory abilities such as speech communication, sound localization, and sound detection. An employee for whom these abilities are impaired may constitute a safety risk for himself or herself, for fellow workers, and possibly for the general public. A number of methods have been used to predict these abilities from diagnostic measures of hearing (e.g., the pure-tone audiogram); however, these methods have not proved to be sufficiently accurate for predicting performance in the noise environments where hearing-critical jobs are performed. We have taken an alternative and potentially more accurate approach. A direct measure of speech intelligibility in noise, the Hearing in Noise Test (HINT), is instead used to screen individuals. The screening criteria are validated by establishing the empirical relationship between the HINT score and the auditory abilities of the individual, as measured in laboratory recreations of real-world workplace noise environments. The psychometric properties of the HINT enable screening of individuals with an acceptable amount of error. In this presentation, we will describe the predictive model and report the results of field measurements and laboratory studies used to provide empirical validation of the model. [Work supported by Fisheries and Oceans Canada.

  8. Modeling and Prediction of the Noise from Non-Axisymmetric Jets

    NASA Technical Reports Server (NTRS)

    Leib, Stewart J.

    2014-01-01

    mean flows which were meant to represent noise reduction concepts being considered by NASA. Testing (Ref. 5) showed that the method was feasible for the types of mean flows of interest in jet noise applications. Subsequently, this method was further developed to allow use of mean flow profiles obtained from a Reynolds-averaged Navier-Stokes (RANS) solution of the flow. Preliminary testing of the generalized code was among the last tasks completed under this contract. The stringent noise-reduction goals of NASA's Fundamental Aeronautics Program suggest that, in addition to potentially complex exhaust nozzle geometries, next generation aircraft will also involve tighter integration of the engine with the airframe. Therefore, noise generated and propagated by jet flows in the vicinity of solid surfaces is expected to be quite significant, and reduced-order noise prediction tools will be needed that can deal with such geometries. One important source of noise is that generated by the interaction of a turbulent jet with the edge of a solid surface (edge noise). Such noise is generated, for example, by the passing of the engine exhaust over a shielding surface, such as a wing. Work under this task supported an effort to develop a RANS-based prediction code for edge noise based on an extension of the classical Rapid Distortion Theory (RDT) to transversely sheared base flows (Refs. 6 and 7). The RDT-based theoretical analysis was applied to the generic problem of a turbulent jet interacting with the trailing edge of a flat plate. A code was written to evaluate the formula derived for the spectrum of the noise produced by this interaction and results were compared with data taken at NASA Glenn for a variety of jet/plate configurations and flow conditions (Ref. 8). A longer-term goal of this task was to work toward the development of a high-fidelity model of sound propagation in spatially developing non-axisymmetric jets using direct numerical methods for solving the relevant

  9. Modelling Aerodynamically Generated Sound: Recent Advances in Rotor Noise Prediction

    NASA Technical Reports Server (NTRS)

    Brentner, Kenneth S.

    2000-01-01

    A great deal of progress has been made in the modeling of aerodynamically generated sound for rotors over the past decade. The Ffowcs Williams-Hawkings (FW-H ) equation has been the foundation for much of the development. Both subsonic and supersonic quadrupole noise formulations have been developed for the prediction of high-speed impulsive noise. In an effort to eliminate the need to compute the quadrupole contribution, the FW-H has also been utilized on permeable surfaces surrounding all physical noise sources. Comparison of the Kirchhoff formulation for moving surfaces with the FW-H equation have shown that the Kirchhoff formulation for moving surfaces can give erroneous results for aeroacoustic problems.

  10. Structural Acoustic Prediction and Interior Noise Control Technology

    NASA Technical Reports Server (NTRS)

    Mathur, G. P.; Chin, C. L.; Simpson, M. A.; Lee, J. T.; Palumbo, Daniel L. (Technical Monitor)

    2001-01-01

    This report documents the results of Task 14, "Structural Acoustic Prediction and Interior Noise Control Technology". The task was to evaluate the performance of tuned foam elements (termed Smart Foam) both analytically and experimentally. Results taken from a three-dimensional finite element model of an active, tuned foam element are presented. Measurements of sound absorption and sound transmission loss were taken using the model. These results agree well with published data. Experimental performance data were taken in Boeing's Interior Noise Test Facility where 12 smart foam elements were applied to a 757 sidewall. Several configurations were tested. Noise reductions of 5-10 dB were achieved over the 200-800 Hz bandwidth of the controller. Accelerometers mounted on the panel provided a good reference for the controller. Configurations with far-field error microphones outperformed near-field cases.

  11. An Assessment of Current Fan Noise Prediction Capability

    NASA Technical Reports Server (NTRS)

    Envia, Edmane; Woodward, Richard P.; Elliott, David M.; Fite, E. Brian; Hughes, Christopher E.; Podboy, Gary G.; Sutliff, Daniel L.

    2008-01-01

    In this paper, the results of an extensive assessment exercise carried out to establish the current state of the art for predicting fan noise at NASA are presented. Representative codes in the empirical, analytical, and computational categories were exercised and assessed against a set of benchmark acoustic data obtained from wind tunnel tests of three model scale fans. The chosen codes were ANOPP, representing an empirical capability, RSI, representing an analytical capability, and LINFLUX, representing a computational aeroacoustics capability. The selected benchmark fans cover a wide range of fan pressure ratios and fan tip speeds, and are representative of modern turbofan engine designs. The assessment results indicate that the ANOPP code can predict fan noise spectrum to within 4 dB of the measurement uncertainty band on a third-octave basis for the low and moderate tip speed fans except at extreme aft emission angles. The RSI code can predict fan broadband noise spectrum to within 1.5 dB of experimental uncertainty band provided the rotor-only contribution is taken into account. The LINFLUX code can predict interaction tone power levels to within experimental uncertainties at low and moderate fan tip speeds, but could deviate by as much as 6.5 dB outside the experimental uncertainty band at the highest tip speeds in some case.

  12. System Noise Prediction of the DGEN 380 Turbofan Engine

    NASA Technical Reports Server (NTRS)

    Berton, Jeffrey J.

    2015-01-01

    The DGEN 380 is a small, separate-flow, geared turbofan. Its manufacturer, Price Induction, is promoting it for a small twinjet application in the emerging personal light jet market. Smaller, and producing less thrust than other entries in the industry, Price Induction is seeking to apply the engine to a 4- to 5-place twinjet designed to compete in an area currently dominated by propeller-driven airplanes. NASA is considering purchasing a DGEN 380 turbofan to test new propulsion noise reduction technologies in a relevant engine environment. To explore this possibility, NASA and Price Induction have signed a Space Act Agreement and have agreed to cooperate on engine acoustic testing. Static acoustic measurements of the engine were made by NASA researchers during July, 2014 at the Glenn Research Center. In the event that a DGEN turbofan becomes a NASA noise technology research testbed, it is in the interest of NASA to develop procedures to evaluate engine system noise metrics. This report documents the procedures used to project the DGEN static noise measurements to flight conditions and the prediction of system noise of a notional airplane powered by twin DGEN engines.

  13. Simulation-Based Prediction of Equivalent Continuous Noises during Construction Processes.

    PubMed

    Zhang, Hong; Pei, Yun

    2016-01-01

    Quantitative prediction of construction noise is crucial to evaluate construction plans to help make decisions to address noise levels. Considering limitations of existing methods for measuring or predicting the construction noise and particularly the equivalent continuous noise level over a period of time, this paper presents a discrete-event simulation method for predicting the construction noise in terms of equivalent continuous level. The noise-calculating models regarding synchronization, propagation and equivalent continuous level are presented. The simulation framework for modeling the noise-affected factors and calculating the equivalent continuous noise by incorporating the noise-calculating models into simulation strategy is proposed. An application study is presented to demonstrate and justify the proposed simulation method in predicting the equivalent continuous noise during construction. The study contributes to provision of a simulation methodology to quantitatively predict the equivalent continuous noise of construction by considering the relevant uncertainties, dynamics and interactions. PMID:27529266

  14. Simulation-Based Prediction of Equivalent Continuous Noises during Construction Processes.

    PubMed

    Zhang, Hong; Pei, Yun

    2016-08-12

    Quantitative prediction of construction noise is crucial to evaluate construction plans to help make decisions to address noise levels. Considering limitations of existing methods for measuring or predicting the construction noise and particularly the equivalent continuous noise level over a period of time, this paper presents a discrete-event simulation method for predicting the construction noise in terms of equivalent continuous level. The noise-calculating models regarding synchronization, propagation and equivalent continuous level are presented. The simulation framework for modeling the noise-affected factors and calculating the equivalent continuous noise by incorporating the noise-calculating models into simulation strategy is proposed. An application study is presented to demonstrate and justify the proposed simulation method in predicting the equivalent continuous noise during construction. The study contributes to provision of a simulation methodology to quantitatively predict the equivalent continuous noise of construction by considering the relevant uncertainties, dynamics and interactions.

  15. Simulation-Based Prediction of Equivalent Continuous Noises during Construction Processes

    PubMed Central

    Zhang, Hong; Pei, Yun

    2016-01-01

    Quantitative prediction of construction noise is crucial to evaluate construction plans to help make decisions to address noise levels. Considering limitations of existing methods for measuring or predicting the construction noise and particularly the equivalent continuous noise level over a period of time, this paper presents a discrete-event simulation method for predicting the construction noise in terms of equivalent continuous level. The noise-calculating models regarding synchronization, propagation and equivalent continuous level are presented. The simulation framework for modeling the noise-affected factors and calculating the equivalent continuous noise by incorporating the noise-calculating models into simulation strategy is proposed. An application study is presented to demonstrate and justify the proposed simulation method in predicting the equivalent continuous noise during construction. The study contributes to provision of a simulation methodology to quantitatively predict the equivalent continuous noise of construction by considering the relevant uncertainties, dynamics and interactions. PMID:27529266

  16. A New Time Domain Formulation for Broadband Noise Predictions

    NASA Technical Reports Server (NTRS)

    Casper, J.; Farassat, F.

    2002-01-01

    A new analytic result in acoustics called "Formulation 1B," proposed by Farassat, is used to compute the loading noise from an unsteady surface pressure distribution on a thin airfoil in the time domain. This formulation is a new solution of the Ffowcs Williams-Hawkings equation with the loading source term. The formulation contains a far field surface integral that depends on the time derivative and the surface gradient of the pressure on the airfoil, as well as a contour integral on the boundary of the airfoil surface. As a first test case, the new formulation is used to compute the noise radiated from a flat plate, moving through a sinusoidal gust of constant frequency. The unsteady surface pressure for this test case is analytically specified from a result based on linear airfoil theory. This test case is used to examine the velocity scaling properties of Formulation 1B and to demonstrate its equivalence to Formulation 1A of Farassat. The new acoustic formulation, again with an analytic surface pressure, is then used to predict broadband noise radiated from an airfoil immersed in homogeneous, isotropic turbulence. The results are compared with experimental data previously reported by Paterson and Amiet. Good agreement between predictions and measurements is obtained. Finally, an alternative form of Formulation 1B is described for statistical analysis of broadband noise.

  17. A New Time Domain Formulation for Broadband Noise Predictions

    NASA Technical Reports Server (NTRS)

    Casper, Jay H.; Farassat, Fereidoun

    2002-01-01

    A new analytic result in acoustics called "Formulation 1B," proposed by Farassat, is used to compute the loading noise from an unsteady surface pressure distribution on a thin airfoil in the time domain. This formulation is a new solution of the Ffowcs Williams-Hawkings equation with the loading source term. The formulation contains a far field surface integral that depends on the time derivative and the surface gradient of the pressure on the airfoil, as well as a contour integral on the boundary of the airfoil surface. As a first test case, the new formulation is used to compute the noise radiated from a flat plate, moving through a sinusoidal gust of constant frequency. The unsteady surface pressure for this test case is analytically specied from a result based on linear airfoil theory. This test case is used to examine the velocity scaling properties of Formulation 1B and to demonstrate its equivalence to Formulation 1A of Farassat. The new acoustic formulation, again with an analytic surface pressure, is then used to predict broadband noise radiated from an airfoil immersed in homogeneous, isotropic turbulence. The results are compared with experimental data previously reported by Paterson and Amiet. Good agreement between predictions and measurements is obtained. Finally, an alternative form of Formulation 1B is described for statistical analysis of broadband noise.

  18. Three-dimensional calculations of rotor-airframe interaction in forward flight

    NASA Technical Reports Server (NTRS)

    Zori, Laith A. J.; Mathur, Sanjay R.; Rajagopalan, R. G.

    1992-01-01

    A method for analyzing the mutual aerodynamic interaction between a rotor and an airframe model has been developed. This technique models the rotor implicitly through the source terms of the momentum equations. A three-dimensional, incompressible, laminar, Navier-Stokes solver in cylindrical coordinates was developed for analyzing the rotor/airframe problem. The calculations are performed on a simplified model at an advance ratio of 0.1. The airframe surface pressure predictions are found to be in good agreement with wind tunnel test data. Results are presented for velocity and pressure field distributions in the wake of the rotor.

  19. Prediction of jet mixing noise in high-speed flight

    NASA Astrophysics Data System (ADS)

    Michel, Ulf; Boettcher, Jan

    A method for the prediction of single stream jet mixing noise in flight is presented that can be used for flight Mach numbers up to 0.9. The method is similar to the empirical SAE method. However, two important results of the theoretical scaling law of Michalke and Michel are incorporated: (1) the total noise of heated jets is separated into quadrupole and dipole noise components because they are influenced differently by the flight Mach number and, (2) the influence of the stretching of the jet plume in flight on the overall sound pressure and the frequency of the emitted sound is considered. A relative velocity exponent law is used to correlate experimental flyover data. The correlation is based on all available data for combat aircraft with fuselage mounted engines and flight Mach numbers between 0.5 and 0.9. The difference between predictions with this new method and measured overall flyover levels is generally less than two decibels. The spectra are also well predicted.

  20. Prediction of jet mixing noise for high subsonic flight speeds

    NASA Astrophysics Data System (ADS)

    Michel, Ulf; Boettcher, Jan

    1992-04-01

    A method for the prediction of single stream jet mixing noise in flight is presented that can be used for flight Mach numbers up to 0.9. The method is similar to the empirical SAE method. However, two important results of the theoretical scaling law of Michalke and Michel are incorporated: (1) the total noise of heated jets is separated into quadrupole and dipole noise components because they are influenced differently by the flight Mach number and, (2) the influence of the stretching of the jet plume in flight on the overall sound pressure and the frequency of the emitted sound is considered. A relative velocity exponent law is used to correlate experimental flyover data. The correlation is based on all available data for combat aircraft with fuselage mounted engines and flight Mach numbers between 0.5 and 0.9. The difference between predictions with this new method and measured overall flyover levels is generally less than two decibels. The spectra are also well predicted.

  1. Computer program to predict noise of general aviation aircraft: User's guide

    NASA Technical Reports Server (NTRS)

    Mitchell, J. A.; Barton, C. K.; Kisner, L. S.; Lyon, C. A.

    1982-01-01

    Program NOISE predicts General Aviation Aircraft far-field noise levels at FAA FAR Part 36 certification conditions. It will also predict near-field and cabin noise levels for turboprop aircraft and static engine component far-field noise levels.

  2. Advanced composite airframe program: Today's technology

    NASA Technical Reports Server (NTRS)

    Good, Danny E.; Mazza, L. Thomas

    1988-01-01

    The Advanced Composite Airframe Program (ACAP) was undertaken to demonstrate the advantages of the application of advanced composite materials and structural design concepts to the airframe structure on helicopters designed to stringent military requirements. The primary goals of the program were the reduction of airframe production costs and airframe weight by 17 and 22 percent respectively. The ACAP effort consisted of a preliminary design phase, detail design, and design support testing, full-scale fabrication, laboratory testing, and a ground/flight test demonstration. Since the completion of the flight test demonstration programs follow-on efforts were initiated to more fully evaluate a variety of military characteristics of the composite airframe structures developed under the original ACAP advanced development contracts. An overview of the ACAP program is provided and some of the design features, design support testing, manufacturing approaches, and the results of the flight test evaluation, as well as, an overview of Militarization Test and Evaluation efforts are described.

  3. Assessment of noise impact on the urban environment: a study on noise-prediction models. Environmental health series

    SciTech Connect

    Lang, J.

    1986-01-01

    The report identifies, compares, and evaluates the major methods developed in Europe and North America to predict noise levels resulting from urban-development projects. Hopefully, it will guide countries that have not yet developed their own noise-prediction models to choose the model most appropriate for their particular situation. It covers prediction methods for road traffic noise and railroad traffic noise in Austria, Czecheslovakia, France, both Germany's Hungary, Netherlands, Scandinavia, Switzerland, U.K. and USA, as well as the Commission of the European Communities, and a comparison of methods. It also covers prediction methods for industrial noise from Austria, both Germany's Netherlands, Scandinavia, and U.K., and discusses calculation methods for aircraft noise around airports.

  4. Jet Mixing Noise Scaling Laws SHJAR Data Vs. Predictions

    NASA Technical Reports Server (NTRS)

    Khavaran, Abbas; Bridges, James

    2008-01-01

    High quality jet noise spectral data measured at the anechoic dome at the NASA Glenn Research Center is used to examine a number of jet noise scaling laws. Configurations considered in the present study consist of convergent as well as convergent-divergent axisymmetric nozzles. The spectral measurements are shown in narrow band and cover 8193 equally spaced points in a typical Strouhal number range of (0.01 10.0). Measurements are reported as lossless (i.e. atmospheric attenuation is added to as-measured data), and at 24 equally spaced angles (50deg to 165deg) on a 100-diameter arc. Following the work of Viswanathan [Ref. 1], velocity power laws are derived using a least square fit on spectral power density as a function of jet temperature and observer angle. The goodness of the fit is studied at each angle, and alternative relationships are proposed to improve the spectral collapse when certain conditions are met. On the application side, power laws are extremely useful in identifying components from various noise generation mechanisms. From this analysis, jet noise prediction tools can be developed with physics derived from the different spectral components.

  5. Prediction of Turbulent Jet Mixing Noise Reduction by Water Injection

    NASA Technical Reports Server (NTRS)

    Kandula, Max

    2008-01-01

    A one-dimensional control volume formulation is developed for the determination of jet mixing noise reduction due to water injection. The analysis starts from the conservation of mass, momentum and energy for the confrol volume, and introduces the concept of effective jet parameters (jet temperature, jet velocity and jet Mach number). It is shown that the water to jet mass flow rate ratio is an important parameter characterizing the jet noise reduction on account of gas-to-droplet momentum and heat transfer. Two independent dimensionless invariant groups are postulated, and provide the necessary relations for the droplet size and droplet Reynolds number. Results are presented illustrating the effect of mass flow rate ratio on the jet mixing noise reduction for a range of jet Mach number and jet Reynolds number. Predictions from the model show satisfactory comparison with available test data on perfectly expanded hot supersonic jets. The results suggest that significant noise reductions can be achieved at increased flow rate ratios.

  6. Analysis of a Shock-Associated Noise Prediction Model Using Measured Jet Far-Field Noise Data

    NASA Technical Reports Server (NTRS)

    Dahl, Milo D.; Sharpe, Jacob A.

    2014-01-01

    A code for predicting supersonic jet broadband shock-associated noise was assessed us- ing a database containing noise measurements of a jet issuing from a convergent nozzle. The jet was operated at 24 conditions covering six fully expanded Mach numbers with four total temperature ratios. To enable comparisons of the predicted shock-associated noise component spectra with data, the measured total jet noise spectra were separated into mixing noise and shock-associated noise component spectra. Comparisons between predicted and measured shock-associated noise component spectra were used to identify de ciencies in the prediction model. Proposed revisions to the model, based on a study of the overall sound pressure levels for the shock-associated noise component of the mea- sured data, a sensitivity analysis of the model parameters with emphasis on the de nition of the convection velocity parameter, and a least-squares t of the predicted to the mea- sured shock-associated noise component spectra, resulted in a new de nition for the source strength spectrum in the model. An error analysis showed that the average error in the predicted spectra was reduced by as much as 3.5 dB for the revised model relative to the average error for the original model.

  7. Analysis of a Shock-Associated Noise Prediction Model Using Measured Jet Far-Field Noise Data

    NASA Technical Reports Server (NTRS)

    Dahl, Milo D.; Sharpe, Jacob A.

    2014-01-01

    A code for predicting supersonic jet broadband shock-associated noise was assessed using a database containing noise measurements of a jet issuing from a convergent nozzle. The jet was operated at 24 conditions covering six fully expanded Mach numbers with four total temperature ratios. To enable comparisons of the predicted shock-associated noise component spectra with data, the measured total jet noise spectra were separated into mixing noise and shock-associated noise component spectra. Comparisons between predicted and measured shock-associated noise component spectra were used to identify deficiencies in the prediction model. Proposed revisions to the model, based on a study of the overall sound pressure levels for the shock-associated noise component of the measured data, a sensitivity analysis of the model parameters with emphasis on the definition of the convection velocity parameter, and a least-squares fit of the predicted to the measured shock-associated noise component spectra, resulted in a new definition for the source strength spectrum in the model. An error analysis showed that the average error in the predicted spectra was reduced by as much as 3.5 dB for the revised model relative to the average error for the original model.

  8. Prediction of the far field noise from wind energy farms

    NASA Technical Reports Server (NTRS)

    Shepherd, K. P.; Hubbard, H. H.

    1986-01-01

    The basic physical factors involved in making predictions of wind turbine noise and an approach which allows for differences in the machines, the wind energy farm configurations and propagation conditions are reviewed. Example calculations to illustrate the sensitivity of the radiated noise to such variables as machine size, spacing and numbers, and such atmosphere variables as absorption and wind direction are presented. It is found that calculated far field distances to particular sound level contours are greater for lower values of atmospheric absorption, for a larger total number of machines, for additional rows of machines and for more powerful machines. At short and intermediate distances, higher sound pressure levels are calculated for closer machine spacings, for more powerful machines, for longer row lengths and for closer row spacings.

  9. Prediction, Measurement, and Suppression of High Temperature Supersonic Jet Noise

    NASA Technical Reports Server (NTRS)

    Seiner, John M.; Bhat, T. R. S.; Jansen, Bernard J.

    1999-01-01

    The photograph in figure 1 displays a water cooled round convergent-divergent supersonic nozzle operating slightly overexpanded near 2460 F. The nozzle is designed to produce shock free flow near this temperature at Mach 2. The exit diameter of this nozzle is 3.5 inches. This nozzle is used in the present study to establish properties of the sound field associated with high temperature supersonic jets operating fully pressure balanced (i.e. shock free) and to evaluate capability of the compressible Rayleigh model to account for principle physical features of the observed sound emission. The experiment is conducted statically (i.e. M(sub f) = 0.) in the NASA/LaRC Jet Noise Laboratory. Both aerodynamic and acoustic measurements are obtained in this study along with numerical plume simulation and theoretical prediction of jet noise. Detailed results from this study are reported previously by Seiner, Ponton, Jansen, and Lagen.

  10. Development of a highway noise prediction model using an Leq20 s measure of basic vehicular noise

    NASA Astrophysics Data System (ADS)

    Pamanikabud, P.; Tansatcha, M.; Brown, A. L.

    2008-09-01

    The objective of the study reported here was to build a highway traffic noise simulation model for free-flow traffic conditions in Thailand employing a technique utilizing individual vehicular noise modelling based on the equivalent sound level over 20 s ( Leq20 s). This Leq20 s technique provides a more accurate measurement of noise energy from each type of vehicle under real running conditions. The coefficient of propagation and ground effect for this model was then estimated using a trial-and-error method, and applied to the highway traffic noise simulation model. This newly developed highway traffic noise model was tested for its goodness-of-fit to field observations. The test shows that this new model provides good predictions for highway noise conditions in Thailand. The concepts and techniques that are modeled and tested in this study can also be applied for prediction of traffic noise for local conditions in other countries.

  11. Jet transport noise - A comparison of predicted and measured noise for ILS and two-segment approaches

    NASA Technical Reports Server (NTRS)

    White, K. C.; Bourquin, K. R.

    1974-01-01

    Centerline noise measured during standard ILS and two-segment approaches in DC-8-61 aircraft were compared with noise predicted for these procedures using an existing noise prediction technique. Measured data is considered to be in good agreement with predicted data. Ninety EPNdB sideline locations were calculated from flight data obtained during two-segment approaches and were compared with predicted 90 EPNdB contours that were computed using three different models for excess ground attenuation and a contour with no correction for ground attenuation. The contour not corrected for ground attenuation was in better agreement with the measured data.

  12. The Role of Instability Waves in Predicting Jet Noise

    NASA Technical Reports Server (NTRS)

    Goldstein, Marvin E.; Handler, Louis M.

    2003-01-01

    Debate over whether linear instability waves play a role in the prediction of jet noise has been going on for many years. Parallel mean flow models, such as the one proposed by Lilley, usually neglect these waves because they cause the solution to become infinite. The present paper solves the true non-parallel acoustic equations for a two-dimensional shear layer by using a vector Greens function and assuming small mean flow spread rate. The results show that linear instability waves must be accounted for in order to construct a proper causal solution to the problem.

  13. Computational AeroAcoustics for Fan Noise Prediction

    NASA Technical Reports Server (NTRS)

    Envia, Ed; Hixon, Ray; Dyson, Rodger; Huff, Dennis (Technical Monitor)

    2002-01-01

    An overview of the current state-of-the-art in computational aeroacoustics as applied to fan noise prediction at NASA Glenn is presented. Results from recent modeling efforts using three dimensional inviscid formulations in both frequency and time domains are summarized. In particular, the application of a frequency domain method, called LINFLUX, to the computation of rotor-stator interaction tone noise is reviewed and the influence of the background inviscid flow on the acoustic results is analyzed. It has been shown that the noise levels are very sensitive to the gradients of the mean flow near the surface and that the correct computation of these gradients for highly loaded airfoils is especially problematic using an inviscid formulation. The ongoing development of a finite difference time marching code that is based on a sixth order compact scheme is also reviewed. Preliminary results from the nonlinear computation of a gust-airfoil interaction model problem demonstrate the fidelity and accuracy of this approach. Spatial and temporal features of the code as well as its multi-block nature are discussed. Finally, latest results from an ongoing effort in the area of arbitrarily high order methods are reviewed and technical challenges associated with implementing correct high order boundary conditions are discussed and possible strategies for addressing these challenges ore outlined.

  14. Toward predicting clay landslide with ambient seismic noise

    NASA Astrophysics Data System (ADS)

    Larose, E. F.; Mainsant, G.; Carriere, S.; Chambon, G.; Michoud, C.; Jongmans, D.; Jaboyedoff, M.

    2013-12-01

    Clay-rich pose critical problems in risk management worldwide. The most widely proposed mechanism leading to such flow-like movements is the increase in water pore pressure in the sliding mass, generating partial or complete liquefaction. This solid-to-liquid transition results in a dramatic reduction of mechanical rigidity, which could be detected by monitoring shear wave velocity variations, The ambient seismic noise correlation technique has been applied to measure the variation in the seismic surface wave velocity in the Pont Bourquin landslide (Swiss Alps). This small but active composite earthslide-earthflow was equipped with continuously recording seismic sensors during spring and summer 2010, and then again from fall 2011 on. An earthslide of a few thousand cubic meters was triggered in mid-August 2010, after a rainy period. This article shows that the seismic velocity of the sliding material, measured from daily noise correlograms, decreased continuously and rapidly for several days prior to the catastrophic event. From a spectral analysis of the velocity decrease, it was possible to determine the location of the change at the base of the sliding layer. These results are confirmed by analogous small-scale experiments in the laboratory. These results demonstrate that ambient seismic noise can be used to detect rigidity variations before failure and could potentially be used to predict landslides.

  15. User's reference guide for Noise Assessment Prediction System (NAPS)

    NASA Astrophysics Data System (ADS)

    Smith, Joyce A.; Luers, James K.; Dietenberger, Mark A.

    1992-07-01

    The noise assessment and prediction system (NAPS) model provides an estimate of the surface peak noise intensity in all directions surrounding a blast source. The model makes use of a personal computer. An essential feature of the model is its ability to account for meteorological and topographical variations in the calculation of blast sound propagation. In performing noise intensity estimates, acoustic ray traces are generated over a sufficient range of azimuth and elevation angles to define the focusing and shadow regions in the area surrounding the airblast. The acoustics of the model include the effects of spherical acoustic spreading, absorption, focusing, shadow zones, reflection of rays from water, interference of multiple rays arriving at the same location, and the directional asymmetry of a blastwave. The NAPS model has been implemented at Aberdeen Proving Ground, Maryland, using acoustic sounder, upper air, and surface station data to provide on-line meteorological input. Plots of ray trace trajectories and sound intensity contour levels on a background map of the Aberdeen area, along with tabular data, are included as model features. This user's reference guide describes the procedures for running the NAPS model. It also includes examples of the required input data files and examples of the graphic outputs generated by the model.

  16. Prediction and reduction of aircraft noise in outdoor environments

    NASA Astrophysics Data System (ADS)

    Tong, Bao N.

    This dissertation investigates the noise due to an en-route aircraft cruising at high altitudes. It offers an improved understanding into the combined effects of atmospheric propagation, ground reflection, and source motion on the impact of en-route aircraft noise. A numerical model has been developed to compute pressure time-histories due to a uniformly moving source above a flat ground surface in the presence of a horizontally stratified atmosphere. For a moving source at high elevations, contributions from a direct and specularly reflected wave are sufficient in predicting the sound field close to the ground. In the absence of wind effects, the predicted sound field from a single overhead flight trajectory can be used to interpolate pressure time histories at all other receiver locations via a simplified ray model for the incoherent sound field. This approach provides an efficient method for generating pressure time histories in a three-dimensional space for noise impact studies. A variety of different noise propagation methods are adapted to a uniformly moving source to evaluate the accuracy and efficiency of their predictions. The techniques include: analytical methods, the Fast Field Program (FFP), and asymptotic analysis methods (e.g., ray tracing and more advanced formulations). Source motion effects are introduced via either a retarded time analysis or a Lorentz transform approach depending on the complexity of the problem. The noise spectrum from a single emission frequency, moving source has broadband characteristics. This is a consequence of the Doppler shift which continuously modifies the perceived frequency of the source as it moves relative to a stationary observer on the ground. Thus, the instantaneous wavefronts must be considered in both the frequency dependent ground impedance model and the atmospheric absorption model. It can be shown that the Doppler factor is invariant along each ray path. This gives rise to a path dependent atmospheric

  17. MPT Prediction of Aircraft-Engine Fan Noise

    NASA Technical Reports Server (NTRS)

    Connell, Stuart D.

    2004-01-01

    A collection of computer programs has been developed that implements a procedure for predicting multiple-pure-tone (MPT) noise generated by fan blades of an aircraft engine (e.g., a turbofan engine). MPT noise arises when the fan is operating with supersonic relative tip Mach No. Under this flow condition, there is a strong upstream running shock. The strength and position of this shock are very sensitive to blade geometry variations. For a fan where all the blades are identical, the primary tone observed upstream of the fan will be the blade passing frequency. If there are small variations in geometry between blades, then tones below the blade passing frequency arise MPTs. Stagger angle differences as small as 0.1 can give rise to significant MPT. It is also noted that MPT noise is more pronounced when the fan is operating in an unstarted mode. Computational results using a three-dimensional flow solver to compute the complete annulus flow with non-uniform fans indicate that MPT noise can be estimated in a relatively simple way. Hence, once the effect of a typical geometry variation of one blade in an otherwise uniform blade row is known, the effect of all the blades being different can be quickly computed via superposition. Two computer programs that were developed as part of this work are used in conjunction with a user s computational fluid dynamics (CFD) code to predict MPT spectra for a fan with a specified set of geometric variations: (1) The first program ROTBLD reads the users CFD solution files for a single blade passage via an API (Application Program Interface). There are options to replicate and perturb the geometry with typical variations stagger, camber, thickness, and pitch. The multi-passage CFD solution files are then written in the user s file format using the API. (2) The second program SUPERPOSE requires two input files: the first is the circumferential upstream pressure distribution extracted from the CFD solution on the multi-passage mesh

  18. High Speed Research Noise Prediction Code (HSRNOISE) User's and Theoretical Manual

    NASA Technical Reports Server (NTRS)

    Golub, Robert (Technical Monitor); Rawls, John W., Jr.; Yeager, Jessie C.

    2004-01-01

    This report describes a computer program, HSRNOISE, that predicts noise levels for a supersonic aircraft powered by mixed flow turbofan engines with rectangular mixer-ejector nozzles. It fully documents the noise prediction algorithms, provides instructions for executing the HSRNOISE code, and provides predicted noise levels for the High Speed Research (HSR) program Technology Concept (TC) aircraft. The component source noise prediction algorithms were developed jointly by Boeing, General Electric Aircraft Engines (GEAE), NASA and Pratt & Whitney during the course of the NASA HSR program. Modern Technologies Corporation developed an alternative mixer ejector jet noise prediction method under contract to GEAE that has also been incorporated into the HSRNOISE prediction code. Algorithms for determining propagation effects and calculating noise metrics were taken from the NASA Aircraft Noise Prediction Program.

  19. Frequency-domain prediction of turbofan noise radiation

    NASA Astrophysics Data System (ADS)

    Özyörük, Y.; Alpman, E.; Ahuja, V.; Long, L. N.

    2004-03-01

    This paper describes a frequency-domain numerical method for predicting noise radiation from ducted fans, including acoustic treatment and non-uniform background flow effects. The method solves the Euler equations linearized about a mean flow in the frequency domain. A pseudo-time derivative term is added to the frequency-domain equations so that a time marching technique can be employed to drive the acoustic field to steady state explicitly. This approach makes distributed parallel computing more viable for equations of this type and will allow for future use of well-known convergence acceleration techniques, such as multigrid, to obtain the solutions efficiently. Simulations of the JT15D static test inlet are performed including the effects of liners, and the results are compared with experimental data. A generic engine geometry is used for demonstrating further the prediction capability of the code, calculating the attenuation effects of different liner impedances and liner installation locations on the radiated sound fields.

  20. Predictability of the coherent-noise model and its applications.

    PubMed

    Sarlis, N V; Christopoulos, S-R G

    2012-05-01

    We study the threshold distribution function of the coherent-noise model for the case of infinite number of agents. This function is piecewise constant with a finite number of steps n. The latter exhibits a 1/f behavior as a function of the order of occurrence of an avalanche and hence versus natural time. An analytic expression of the expectation value E(S) for the size S of the next avalanche is obtained and used for the prediction of the next avalanche. Apart from E(S), the number of steps n can also serve for this purpose. This enables the construction of a similar prediction scheme which can be applied to real earthquake aftershock data.

  1. Progress Toward Improving Jet Noise Predictions in Hot Jets

    NASA Technical Reports Server (NTRS)

    Khavaran, Abbas; Kenzakowski, Donald C.

    2007-01-01

    An acoustic analogy methodology for improving noise predictions in hot round jets is presented. Past approaches have often neglected the impact of temperature fluctuations on the predicted sound spectral density, which could be significant for heated jets, and this has yielded noticeable acoustic under-predictions in such cases. The governing acoustic equations adopted here are a set of linearized, inhomogeneous Euler equations. These equations are combined into a single third order linear wave operator when the base flow is considered as a locally parallel mean flow. The remaining second-order fluctuations are regarded as the equivalent sources of sound and are modeled. It is shown that the hot jet effect may be introduced primarily through a fluctuating velocity/enthalpy term. Modeling this additional source requires specialized inputs from a RANS-based flowfield simulation. The information is supplied using an extension to a baseline two equation turbulence model that predicts total enthalpy variance in addition to the standard parameters. Preliminary application of this model to a series of unheated and heated subsonic jets shows significant improvement in the acoustic predictions at the 90 degree observer angle.

  2. Three-dimensional effects on pure tone fan noise due to inflow distortion. [rotor blade noise prediction

    NASA Technical Reports Server (NTRS)

    Kobayashi, H.

    1978-01-01

    Two dimensional, quasi three dimensional and three dimensional theories for the prediction of pure tone fan noise due to the interaction of inflow distortion with a subsonic annular blade row were studied with the aid of an unsteady three dimensional lifting surface theory. The effects of compact and noncompact source distributions on pure tone fan noise in an annular cascade were investigated. Numerical results show that the strip theory and quasi three-dimensional theory are reasonably adequate for fan noise prediction. The quasi three-dimensional method is more accurate for acoustic power and model structure prediction with an acoustic power estimation error of about plus or minus 2db.

  3. Noise Scaling and Community Noise Metrics for the Hybrid Wing Body Aircraft

    NASA Technical Reports Server (NTRS)

    Burley, Casey L.; Brooks, Thomas F.; Hutcheson, Florence V.; Doty, Michael J.; Lopes, Leonard V.; Nickol, Craig L.; Vicroy, Dan D.; Pope, D. Stuart

    2014-01-01

    An aircraft system noise assessment was performed for the hybrid wing body aircraft concept, known as the N2A-EXTE. This assessment is a result of an effort by NASA to explore a realistic HWB design that has the potential to substantially reduce noise and fuel burn. Under contract to NASA, Boeing designed the aircraft using practical aircraft design princip0les with incorporation of noise technologies projected to be available in the 2020 timeframe. NASA tested 5.8% scale-mode of the design in the NASA Langley 14- by 22-Foot Subsonic Tunnel to provide source noise directivity and installation effects for aircraft engine and airframe configurations. Analysis permitted direct scaling of the model-scale jet, airframe, and engine shielding effect measurements to full-scale. Use of these in combination with ANOPP predictions enabled computations of the cumulative (CUM) noise margins relative to FAA Stage 4 limits. The CUM margins were computed for a baseline N2A-EXTE configuration and for configurations with added noise reduction strategies. The strategies include reduced approach speed, over-the-rotor line and soft-vane fan technologies, vertical tail placement and orientation, and modified landing gear designs with fairings. Combining the inherent HWB engine shielding by the airframe with added noise technologies, the cumulative noise was assessed at 38.7 dB below FAA Stage 4 certification level, just 3.3 dB short of the NASA N+2 goal of 42 dB. This new result shows that the NASA N+2 goal is approachable and that significant reduction in overall aircraft noise is possible through configurations with noise reduction technologies and operational changes.

  4. Development of a shock noise prediction code for high-speed helicopters - The subsonically moving shock

    NASA Technical Reports Server (NTRS)

    Tadghighi, H.; Holz, R.; Farassat, F.; Lee, Yung-Jang

    1991-01-01

    A previously defined airfoil subsonic shock-noise prediction formula whose result depends on a mapping of the time-dependent shock surface to a time-independent computational domain is presently coded and incorporated in the NASA-Langley rotor-noise prediction code, WOPWOP. The structure and algorithms used in the shock-noise prediction code are presented; special care has been taken to reduce computation time while maintaining accuracy. Numerical examples of shock-noise prediction are presented for hover and forward flight. It is confirmed that shock noise is an important component of the quadrupole source.

  5. An introduction to high speed aircraft noise prediction

    NASA Technical Reports Server (NTRS)

    Wilson, Mark R.

    1992-01-01

    The Aircraft Noise Prediction Program's High Speed Research prediction system (ANOPP-HSR) is introduced. This mini-manual is an introduction which gives a brief overview of the ANOPP system and the components of the HSR prediction method. ANOPP information resources are given. Twelve of the most common ANOPP-HSR control statements are described. Each control statement's purpose and format are stated and relevant examples are provided. More detailed examples of the use of the control statements are presented in the manual along with ten ANOPP-HSR templates. The purpose of the templates is to provide the user with working ANOPP-HSR programs which can be modified to serve particular prediction requirements. Also included in this manual is a brief discussion of common errors and how to solve these problems. The appendices include the following useful information: a summary of all ANOPP-HSR functional research modules, a data unit directory, a discussion of one of the more complex control statements, and input data unit and table examples.

  6. Impact Testing and Simulation of Composite Airframe Structures

    NASA Technical Reports Server (NTRS)

    Jackson, Karen E.; Littell, Justin D.; Horta, Lucas G.; Annett, Martin S.; Fasanella, Edwin L.; Seal, Michael D., II

    2014-01-01

    Dynamic tests were performed at NASA Langley Research Center on composite airframe structural components of increasing complexity to evaluate their energy absorption behavior when subjected to impact loading. A second objective was to assess the capabilities of predicting the dynamic response of composite airframe structures, including damage initiation and progression, using a state-of-the-art nonlinear, explicit transient dynamic finite element code, LS-DYNA. The test specimens were extracted from a previously tested composite prototype fuselage section developed and manufactured by Sikorsky Aircraft Corporation under the US Army's Survivable Affordable Repairable Airframe Program (SARAP). Laminate characterization testing was conducted in tension and compression. In addition, dynamic impact tests were performed on several components, including I-beams, T-sections, and cruciform sections. Finally, tests were conducted on two full-scale components including a subfloor section and a framed fuselage section. These tests included a modal vibration and longitudinal impact test of the subfloor section and a quasi-static, modal vibration, and vertical drop test of the framed fuselage section. Most of the test articles were manufactured of graphite unidirectional tape composite with a thermoplastic resin system. However, the framed fuselage section was constructed primarily of a plain weave graphite fabric material with a thermoset resin system. Test data were collected from instrumentation such as accelerometers and strain gages and from full-field photogrammetry.

  7. Investigation of the Jet Noise Prediction Theory and Application Utilizing the PAO Formulation. [mathematical model for calculating noise radiation

    NASA Technical Reports Server (NTRS)

    1973-01-01

    Application of the Phillips theory to engineering calculations of rocket and high speed jet noise radiation is reported. Presented are a detailed derivation of the theory, the composition of the numerical scheme, and discussions of the practical problems arising in the application of the present noise prediction method. The present method still contains some empirical elements, yet it provides a unified approach in the prediction of sound power, spectrum, and directivity.

  8. The Role of Instability Waves in Predicting Jet Noise

    NASA Technical Reports Server (NTRS)

    Goldstein, M. E.; Leib, S. J.

    2004-01-01

    There has been an ongoing debate about the role of linear instability waves in the prediction of jet noise. Parallel mean flow models, such as the one proposed by Lilley, usually neglect these waves because they cause the solution to become infinite. The resulting solution is then non-causal and can, therefore, be quite different from the true causal solution for the chaotic flows being considered here. The present paper solves the relevant acoustic equations for a non-parallel mean flow by using a vector Green s function approach and assuming the mean flow to be weakly non-parallel, i.e., assuming the spread rate to be small. It demonstrates that linear instability waves must be accounted for in order to construct a proper causal solution to the jet noise problem. . Recent experimental results (e.g., see Tam, Golebiowski, and Seiner,1996) show that the small angle spectra radiated by supersonic jets are quite different from those radiated at larger angles (say, at 90deg) and even exhibit dissimilar frequency scalings (i.e., they scale with Helmholtz number as opposed to Strouhal number). The present solution is (among other things )able to explain this rather puzzling experimental result.

  9. Auralization Architectures for NASA?s Next Generation Aircraft Noise Prediction Program

    NASA Technical Reports Server (NTRS)

    Rizzi, Stephen A.; Lopes, Leonard V.; Burley, Casey L.; Aumann, Aric R.

    2013-01-01

    Aircraft community noise is a significant concern due to continued growth in air traffic, increasingly stringent environmental goals, and operational limitations imposed by airport authorities. The assessment of human response to noise from future aircraft can only be afforded through laboratory testing using simulated flyover noise. Recent work by the authors demonstrated the ability to auralize predicted flyover noise for a state-of-the-art reference aircraft and a future hybrid wing body aircraft concept. This auralization used source noise predictions from NASA's Aircraft NOise Prediction Program (ANOPP) as input. The results from this process demonstrated that auralization based upon system noise predictions is consistent with, and complementary to, system noise predictions alone. To further develop and validate the auralization process, improvements to the interfaces between the synthesis capability and the system noise tools are required. This paper describes the key elements required for accurate noise synthesis and introduces auralization architectures for use with the next-generation ANOPP (ANOPP2). The architectures are built around a new auralization library and its associated Application Programming Interface (API) that utilize ANOPP2 APIs to access data required for auralization. The architectures are designed to make the process of auralizing flyover noise a common element of system noise prediction.

  10. An efficient feedback active noise control algorithm based on reduced-order linear predictive modeling of FMRI acoustic noise.

    PubMed

    Kannan, Govind; Milani, Ali A; Panahi, Issa M S; Briggs, Richard W

    2011-12-01

    Functional magnetic resonance imaging (fMRI) acoustic noise exhibits an almost periodic nature (quasi-periodicity) due to the repetitive nature of currents in the gradient coils. Small changes occur in the waveform in consecutive periods due to the background noise and slow drifts in the electroacoustic transfer functions that map the gradient coil waveforms to the measured acoustic waveforms. The period depends on the number of slices per second, when echo planar imaging (EPI) sequencing is used. Linear predictability of fMRI acoustic noise has a direct effect on the performance of active noise control (ANC) systems targeted to cancel the acoustic noise. It is shown that by incorporating some samples from the previous period, very high linear prediction accuracy can be reached with a very low order predictor. This has direct implications on feedback ANC systems since their performance is governed by the predictability of the acoustic noise to be cancelled. The low complexity linear prediction of fMRI acoustic noise developed in this paper is used to derive an effective and low-cost feedback ANC system.

  11. Small Engine Technology (SET) - Task 13 ANOPP Noise Prediction for Small Engines: Jet Noise Prediction Module, Wing Shielding Module, and System Studies Results

    NASA Technical Reports Server (NTRS)

    Lieber, Lysbeth; Golub, Robert (Technical Monitor)

    2000-01-01

    This Final Report has been prepared by AlliedSignal Engines and Systems, Phoenix, Arizona, documenting work performed during the period May 1997 through June 1999, under the Small Engines Technology Program, Contract No. NAS3-27483, Task Order 13, ANOPP Noise Prediction for Small Engines. The report specifically covers the work performed under Subtasks 4, 5 and 6. Subtask 4 describes the application of a semi-empirical procedure for jet noise prediction, subtask 5 describes the development of a procedure to predict the effects of wing shielding, and subtask 6 describes the results of system studies of the benefits of the new noise technology on business and regional aircraft.

  12. Comparison of classical statistical methods and artificial neural network in traffic noise prediction

    SciTech Connect

    Nedic, Vladimir; Despotovic, Danijela; Cvetanovic, Slobodan; Despotovic, Milan; Babic, Sasa

    2014-11-15

    Traffic is the main source of noise in urban environments and significantly affects human mental and physical health and labor productivity. Therefore it is very important to model the noise produced by various vehicles. Techniques for traffic noise prediction are mainly based on regression analysis, which generally is not good enough to describe the trends of noise. In this paper the application of artificial neural networks (ANNs) for the prediction of traffic noise is presented. As input variables of the neural network, the proposed structure of the traffic flow and the average speed of the traffic flow are chosen. The output variable of the network is the equivalent noise level in the given time period L{sub eq}. Based on these parameters, the network is modeled, trained and tested through a comparative analysis of the calculated values and measured levels of traffic noise using the originally developed user friendly software package. It is shown that the artificial neural networks can be a useful tool for the prediction of noise with sufficient accuracy. In addition, the measured values were also used to calculate equivalent noise level by means of classical methods, and comparative analysis is given. The results clearly show that ANN approach is superior in traffic noise level prediction to any other statistical method. - Highlights: • We proposed an ANN model for prediction of traffic noise. • We developed originally designed user friendly software package. • The results are compared with classical statistical methods. • The results are much better predictive capabilities of ANN model.

  13. Development of rotorcraft interior noise control concepts. Phase 3: Development of noise control concepts

    NASA Technical Reports Server (NTRS)

    Yoerkie, Charles A.; Gintoli, P. J.; Ingraham, S. T.; Moore, J. A.

    1986-01-01

    The goal of this research is the understanding of helicopter internal noise mechanisms and the development, design, and testing of noise control concepts which will produce significant reductions in the acoustic environment to which passengers are exposed. The Phase 3 effort involved the identification and evaluation of current and advanced treatment concepts, including isolation of structure-borne paths. In addition, a plan was devised for the full-scale evaluation of an isolation concept. Specific objectives were as follows: (1) identification and characterization of various noise control concepts; (2) implementation of noise control concepts within the S-76 SEA (statistical energy analysis) model; (3) definition and evaluation of a preliminary acoustic isolation design to reduce structure-borne transmission of acoustic frequency main gearbox gear clash vibrations into the airframe; (4) formulation of a plan for the full-scale validation of the isolation concept; and (5) prediction of the cabin noise environment with various noise control concepts installed.

  14. ANOPP Landing Gear Noise Prediction Comparisons to Model-scale Data

    NASA Technical Reports Server (NTRS)

    Burley, Casey L.; Brooks, Thomas F.; Humphreys, William M., Jr.; Rawls, John W., Jr.

    2007-01-01

    The NASA Aircraft NOise Prediction Program (ANOPP) includes two methods for computing the noise from landing gear: the "Fink" method and the "Guo" method. Both methods have been predominately validated and used to predict full-scale landing gear noise. The two methods are compared, and their ability to predict the noise for model-scale landing gear is investigated. Predictions are made using both the Fink and Guo methods and compared to measured acoustic data obtained for a high-fidelity, 6.3%-scale, Boeing 777 main landing gear. A process is developed by which full-scale predictions can be scaled to compare with model-scale data. The measurements were obtained in the NASA Langley Quiet Flow Facility for a range of Mach numbers at a large number of observer polar (flyover) and azimuthal (sideline) observer angles. Spectra and contours of the measured sound pressure levels as a function of polar and azimuthal angle characterize the directivity of landing gear noise. Comparisons of predicted noise spectra and contours from each ANOPP method are made. Both methods predict comparable amplitudes and trends for the flyover locations, but deviate at the sideline locations. Neither method fully captures the measured noise directivity. The availability of these measured data provides the opportunity to further understand and advance noise prediction capabilities, particularly for noise directivity.

  15. Applications of aero-acoustics to wind turbine noise prediction and control

    NASA Astrophysics Data System (ADS)

    Lowson, Martin V.

    1993-01-01

    Wind turbine noise generation mechanisms are essentially equivalent to the aero-acoustic mechanisms of other rotors, which have been studied in depth for many years. Basic sources for the wind turbine noise radiation process are defined, and their significance assessed. From the analysis, areas of potential improvement in wind turbine noise prediction are defined. Suggestions are made for approaches to wind turbine noise control which separate the noise problems at cut-in from those at rated power. Some of these offer the possibility of noise reduction without unfavourable effects on performance.

  16. Supersonic jet noise - Its generation, prediction and effects on people and structures

    NASA Technical Reports Server (NTRS)

    Preisser, J. S.; Golub, R. A.; Seiner, J. M.; Powell, C. A.

    1990-01-01

    This paper presents the results of a study aimed at quantifying the effects of jet source noise reduction, increases in aircraft lift, and reduced aircraft thrust on the take-off noise associated with supersonic civil transports. Supersonic jet noise sources are first described, and their frequency and directivity dependence are defined. The study utilizes NASA's Aircraft Noise Prediction Program in a parametric study to weigh the relative benefits of several approaches to low noise. The baseline aircraft concept used in these predictions is the AST-205-1 powered by GE21/J11-B14A scaled engines. Noise assessment is presented in terms of effective perceived noise levels at the FAA's centerline and sideline measuring locations for current subsonic aircraft, and in terms of audiologically perceived sound of people and other indirect effects. The results show that significant noise benefit can be achieved through proper understanding and utilization of all available approaches.

  17. Prediction of unsuppressed jet engine exhaust noise in flight from static data

    NASA Technical Reports Server (NTRS)

    Stone, J. R.

    1980-01-01

    A methodology developed for predicting in-flight exhaust noise from static data is presented and compared with experimental data for several unsuppressed turbojet engines. For each engine, static data over a range of jet velocities are compared with the predicted jet mixing noise and shock-cell noise. The static engine noise over and above the jet and shock noises is identified as excess noise. The excess noise data are then empirically correlated to smooth the spectral and directivity relations and account for variations in test conditions. This excess noise is then projected to flight based on the assumption that the only effects of flight are a Doppler frequency shift and a level change given by 40 log (1 - m sub 0 cos theta), where M sub 0 is the flight Mach number and theta is the observer angle relative to the jet axis.

  18. The status of airport noise prediction, with special reference to the United Kingdom and Europe

    NASA Astrophysics Data System (ADS)

    Large, J. B.; House, M. E.

    1981-08-01

    The current status of airport noise prediction is reviewed with reference to both air-to-ground noise and near-ground noise such as noise generated by road traffic, auxiliary power units, engine ground running, approaching aircraft, and aircraft on taxiways and aprons. Methodologies for contour calculation and assessment are outlined, and areas for further study and refinement of procedures are indicated. In particular, the need for greater accuracy is emphasized in assessments made for legislative and statutory purposes.

  19. RETRACTED: Flap side edge noise modeling and prediction

    NASA Astrophysics Data System (ADS)

    Guo, Yueping

    2013-08-01

    This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy).This article has been retracted at the request of the first author because of the overlap with previously published papers. The first author takes full responsibility and sincerely apologizes for the error made.This article has been retracted at the request of the Editor-in-Chief.The article duplicates significant parts of an earlier paper by the same author, published in AIAA (Y.P. Guo, Aircraft flap side edge noise modeling and prediction. American Institute of Aeronautics and Astronautics, (2011), 10.2514/6.2011-2731). Prior to republication, conference papers should be comprehensively extended, and re-use of any data should be appropriately cited. As such this article represents a severe abuse of the scientific publishing system. The scientific community takes a very strong view on this matter and apologies are offered to readers of the journal that this was not detected during the submission process.

  20. New Computational Methods for the Prediction and Analysis of Helicopter Noise

    NASA Technical Reports Server (NTRS)

    Strawn, Roger C.; Oliker, Leonid; Biswas, Rupak

    1996-01-01

    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.

  1. A noise level prediction method based on electro-mechanical frequency response function for capacitors.

    PubMed

    Zhu, Lingyu; Ji, Shengchang; Shen, Qi; Liu, Yuan; Li, Jinyu; Liu, Hao

    2013-01-01

    The capacitors in high-voltage direct-current (HVDC) converter stations radiate a lot of audible noise which can reach higher than 100 dB. The existing noise level prediction methods are not satisfying enough. In this paper, a new noise level prediction method is proposed based on a frequency response function considering both electrical and mechanical characteristics of capacitors. The electro-mechanical frequency response function (EMFRF) is defined as the frequency domain quotient of the vibration response and the squared capacitor voltage, and it is obtained from impulse current experiment. Under given excitations, the vibration response of the capacitor tank is the product of EMFRF and the square of the given capacitor voltage in frequency domain, and the radiated audible noise is calculated by structure acoustic coupling formulas. The noise level under the same excitations is also measured in laboratory, and the results are compared with the prediction. The comparison proves that the noise prediction method is effective.

  2. Maneuvering Rotorcraft Noise Prediction: A New Code for a New Problem

    NASA Technical Reports Server (NTRS)

    Brentner, Kenneth S.; Bres, Guillaume A.; Perez, Guillaume; Jones, Henry E.

    2002-01-01

    This paper presents the unique aspects of the development of an entirely new maneuver noise prediction code called PSU-WOPWOP. The main focus of the code is the aeroacoustic aspects of the maneuver noise problem, when the aeromechanical input data are provided (namely aircraft and blade motion, blade airloads). The PSU-WOPWOP noise prediction capability was developed for rotors in steady and transient maneuvering flight. Featuring an object-oriented design, the code allows great flexibility for complex rotor configuration and motion (including multiple rotors and full aircraft motion). The relative locations and number of hinges, flexures, and body motions can be arbitrarily specified to match the any specific rotorcraft. An analysis of algorithm efficiency is performed for maneuver noise prediction along with a description of the tradeoffs made specifically for the maneuvering noise problem. Noise predictions for the main rotor of a rotorcraft in steady descent, transient (arrested) descent, hover and a mild "pop-up" maneuver are demonstrated.

  3. Validation of Aircraft Noise Prediction Models at Low Levels of Exposure

    NASA Technical Reports Server (NTRS)

    Page, Juliet A.; Hobbs, Christopher M.; Plotkin, Kenneth J.; Stusnick, Eric; Shepherd, Kevin P. (Technical Monitor)

    2000-01-01

    Aircraft noise measurements were made at Denver International Airport for a period of four weeks. Detailed operational information was provided by airline operators which enabled noise levels to be predicted using the FAA's Integrated Noise Model. Several thrust prediction techniques were evaluated. Measured sound exposure levels for departure operations were found to be 4 to 10 dB higher than predicted, depending on the thrust prediction technique employed. Differences between measured and predicted levels are shown to be related to atmospheric conditions present at the aircraft altitude.

  4. 14 CFR 65.85 - Airframe rating; additional privileges.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... (CONTINUED) AIRMEN CERTIFICATION: AIRMEN OTHER THAN FLIGHT CREWMEMBERS Mechanics § 65.85 Airframe rating; additional privileges. (a) Except as provided in paragraph (b) of this section, a certificated mechanic with...) A certificated mechanic with an airframe rating can approve and return to service an airframe,...

  5. On the prediction of impact noise, part VIII: Diesel engine noise

    NASA Astrophysics Data System (ADS)

    Cuschieri, J. M.; Richards, E. J.

    1985-09-01

    The noise energy radiated from a diesel engine due to combustion and piston slap excitation is investigated by considering single impacts. From the results obtained, possible methods of noise control are studied, and the expected results due to changes in the liner mounting to the engine frame, and the bearings of the camshaft for an injected engine, are compared to the measured noise levels. This proves to be very successful and radical modifications in the engine for noise control can be investigated in this way prior to full development of the prototype engine.

  6. Auditory Brainstem Response to Complex Sounds Predicts Self-Reported Speech-in-Noise Performance

    ERIC Educational Resources Information Center

    Anderson, Samira; Parbery-Clark, Alexandra; White-Schwoch, Travis; Kraus, Nina

    2013-01-01

    Purpose: To compare the ability of the auditory brainstem response to complex sounds (cABR) to predict subjective ratings of speech understanding in noise on the Speech, Spatial, and Qualities of Hearing Scale (SSQ; Gatehouse & Noble, 2004) relative to the predictive ability of the Quick Speech-in-Noise test (QuickSIN; Killion, Niquette,…

  7. Comparison of Predicted and Measured Attenuation of Turbine Noise from a Static Engine Test

    NASA Technical Reports Server (NTRS)

    Chien, Eugene W.; Ruiz, Marta; Yu, Jia; Morin, Bruce L.; Cicon, Dennis; Schwieger, Paul S.; Nark, Douglas M.

    2007-01-01

    Aircraft noise has become an increasing concern for commercial airlines. Worldwide demand for quieter aircraft is increasing, making the prediction of engine noise suppression one of the most important fields of research. The Low-Pressure Turbine (LPT) can be an important noise source during the approach condition for commercial aircraft. The National Aeronautics and Space Administration (NASA), Pratt & Whitney (P&W), and Goodrich Aerostructures (Goodrich) conducted a joint program to validate a method for predicting turbine noise attenuation. The method includes noise-source estimation, acoustic treatment impedance prediction, and in-duct noise propagation analysis. Two noise propagation prediction codes, Eversman Finite Element Method (FEM) code [1] and the CDUCT-LaRC [2] code, were used in this study to compare the predicted and the measured turbine noise attenuation from a static engine test. In this paper, the test setup, test configurations and test results are detailed in Section II. A description of the input parameters, including estimated noise modal content (in terms of acoustic potential), and acoustic treatment impedance values are provided in Section III. The prediction-to-test correlation study results are illustrated and discussed in Section IV and V for the FEM and the CDUCT-LaRC codes, respectively, and a summary of the results is presented in Section VI.

  8. Airport noise predicts song timing of European birds.

    PubMed

    Dominoni, Davide M; Greif, Stefan; Nemeth, Erwin; Brumm, Henrik

    2016-09-01

    Anthropogenic noise is of increasing concern to biologists and medical scientists. Its detrimental effects on human health have been well studied, with the high noise levels from air traffic being of particular concern. However, less is known about the effects of airport noise pollution on signal masking in wild animals. Here, we report a relationship between aircraft noise and two major features of the singing behavior of birds. We found that five of ten songbird species began singing significantly earlier in the morning in the vicinity of a major European airport than their conspecifics at a quieter control site. As birds at both sites started singing before the onset of air traffic in the morning, this suggests that the birds in the vicinity of the airport advanced their activity to gain more time for unimpaired singing before the massive plane noise set in. In addition, we found that during the day, chaffinches avoided singing during airplane takeoffs, but only when the noise exceeded a certain threshold, further suggesting that the massive noise caused by the airport can impair acoustic communication in birds. Overall, our study indicates that birds may be adjusting their mating signals and time budgets in response to aircraft noise.

  9. Airport noise predicts song timing of European birds.

    PubMed

    Dominoni, Davide M; Greif, Stefan; Nemeth, Erwin; Brumm, Henrik

    2016-09-01

    Anthropogenic noise is of increasing concern to biologists and medical scientists. Its detrimental effects on human health have been well studied, with the high noise levels from air traffic being of particular concern. However, less is known about the effects of airport noise pollution on signal masking in wild animals. Here, we report a relationship between aircraft noise and two major features of the singing behavior of birds. We found that five of ten songbird species began singing significantly earlier in the morning in the vicinity of a major European airport than their conspecifics at a quieter control site. As birds at both sites started singing before the onset of air traffic in the morning, this suggests that the birds in the vicinity of the airport advanced their activity to gain more time for unimpaired singing before the massive plane noise set in. In addition, we found that during the day, chaffinches avoided singing during airplane takeoffs, but only when the noise exceeded a certain threshold, further suggesting that the massive noise caused by the airport can impair acoustic communication in birds. Overall, our study indicates that birds may be adjusting their mating signals and time budgets in response to aircraft noise. PMID:27648232

  10. Measurements and predictions of flyover and static noise of a TF30 afterburning turbofan engine

    NASA Technical Reports Server (NTRS)

    Burcham, F. W., Jr.; Lasagna, P. L.; Oas, S. C.

    1978-01-01

    The noise of the TF30 afterburning turbofan engine in an F-111 airplane was determined from static (ground) and flyover tests. A survey was made to measure the exhaust temperature and velocity profiles for a range of power settings. Comparisons were made between predicted and measured jet mixing, internal, and shock noise. It was found that the noise produced at static conditions was dominated by jet mixing noise, and was adequately predicted by current methods. The noise produced during flyovers exhibited large contributions from internally generated noise in the forward arc. For flyovers with the engine at nonafterburning power, the internal noise, shock noise, and jet mixing noise were accurately predicted. During flyovers with afterburning power settings, however, additional internal noise believed to be due to the afterburning process was evident; its level was as much as 8 decibels above the nonafterburning internal noise. Power settings that produced exhausts with inverted velocity profiles appeared to be slightly less noisy than power settings of equal thrust that produced uniform exhaust velocity profiles both in flight and in static testing.

  11. Improved NASA-ANOPP Noise Prediction Computer Code for Advanced Subsonic Propulsion Systems

    NASA Technical Reports Server (NTRS)

    Kontos, K. B.; Janardan, B. A.; Gliebe, P. R.

    1996-01-01

    Recent experience using ANOPP to predict turbofan engine flyover noise suggests that it over-predicts overall EPNL by a significant amount. An improvement in this prediction method is desired for system optimization and assessment studies of advanced UHB engines. An assessment of the ANOPP fan inlet, fan exhaust, jet, combustor, and turbine noise prediction methods is made using static engine component noise data from the CF6-8OC2, E(3), and QCSEE turbofan engines. It is shown that the ANOPP prediction results are generally higher than the measured GE data, and that the inlet noise prediction method (Heidmann method) is the most significant source of this overprediction. Fan noise spectral comparisons show that improvements to the fan tone, broadband, and combination tone noise models are required to yield results that more closely simulate the GE data. Suggested changes that yield improved fan noise predictions but preserve the Heidmann model structure are identified and described. These changes are based on the sets of engine data mentioned, as well as some CFM56 engine data that was used to expand the combination tone noise database. It should be noted that the recommended changes are based on an analysis of engines that are limited to single stage fans with design tip relative Mach numbers greater than one.

  12. Evaluation and prediction of blade-passing frequency noise generated by a centrifugal blower

    SciTech Connect

    Ohta, Y.; Outa, E.; Tajima, K.

    1996-07-01

    The blade-passing frequency noise, abbreviated to BPF noise, of a low-specific-speed centrifugal blower is analyzed by separating the frequency response of the transmission passage and the intensity of the noise source. Frequency response has previously been evaluated by the authors using a one-dimensional linear wave model, and the results have agreed well with the experimental response in a practical range of the blower speed. In the present study, the intensity of the noise source is estimated by introducing the quasi-steady model of the blade wake impingement on the scroll surface. The effective location of the noise source is determined by analyzing the cross-correlation between measured data of the blower suction noise and pressure fluctuation on the scroll surface. Then, the surface density distribution of a dipole noise source is determined from pressure fluctuations expressed in terms of quasi-steady dynamic pressure of the traveling blade wake. Finally, the free-field noise level is predicted by integrating the density spectrum of the noise source over the effective source area. The sound pressure level of the blower suction noise is easily predicted by multiplying the free-field noise level by the frequency-response characteristics of the noise transmission passage.

  13. Image discrimination models predict detection in fixed but not random noise

    NASA Technical Reports Server (NTRS)

    Ahumada, A. J. Jr; Beard, B. L.; Watson, A. B. (Principal Investigator)

    1997-01-01

    By means of a two-interval forced-choice procedure, contrast detection thresholds for an aircraft positioned on a simulated airport runway scene were measured with fixed and random white-noise masks. The term fixed noise refers to a constant, or unchanging, noise pattern for each stimulus presentation. The random noise was either the same or different in the two intervals. Contrary to simple image discrimination model predictions, the same random noise condition produced greater masking than the fixed noise. This suggests that observers seem unable to hold a new noisy image for comparison. Also, performance appeared limited by internal process variability rather than by external noise variability, since similar masking was obtained for both random noise types.

  14. On INM's Use of Corrected Net Thrust for the Prediction of Jet Aircraft Noise

    NASA Technical Reports Server (NTRS)

    McAninch, Gerry L.; Shepherd, Kevin P.

    2011-01-01

    The Federal Aviation Administration s (FAA) Integrated Noise Model (INM) employs a prediction methodology that relies on corrected net thrust as the sole correlating parameter between aircraft and engine operating states and aircraft noise. Thus aircraft noise measured for one set of atmospheric and aircraft operating conditions is assumed to be applicable to all other conditions as long as the corrected net thrust remains constant. This hypothesis is investigated under two primary assumptions: (1) the sound field generated by the aircraft is dominated by jet noise, and (2) the sound field generated by the jet flow is adequately described by Lighthill s theory of noise generated by turbulence.

  15. [Prediction and influence factors of the ramp's noise of the entrance or exit of garages].

    PubMed

    Di, Guo-Qing; Zhang, Bang-Jun

    2005-09-01

    Some typical entrances/exits of the underground garages are chosen in urban residential areas. On the basis of the optimization of the positions of the noise sampling points and the groupings of the synchronous sampling points, by means of the acoustical analysis of the noise samples, the relation of the correlative factors, among the ramps' noise of the entrances or exits of the garages, the structure, grade, shape of the ramps, upgrade and downgrade, is studied. The prediction model of the ramp's noise influence of the entrance or exit of the garage is established through amending the noise influence of the entrance or exit of the even concrete road. PMID:16366500

  16. A prediction method for broadband shock associated noise from supersonic rectangualr jets

    NASA Technical Reports Server (NTRS)

    Tam, Christopher K. W.; Reddy, N. N.

    1993-01-01

    Braodband shock associated noise is an important aircraft noise component of the proposed high-speed civil transport (HSCT) at take-offs and landings. For noise certification purpose one would, therefore, like to be able to predict as accurately as possible the intensity, directivity and spectral content of this noise component. The purpose of this work is to develop a semi-empirical prediction method for the broadband shock associated noise from supersonic rectangular jets. The complexity and quality of the noise prediction method are to be similar to those for circular jets. In this paper only the broadband shock associated noise of jets issued from rectangular nozzles with straight side walls is considered. Since many current aircraft propulsion systems have nozzle aspect ratios (at nozzle exit) in the range of 1 to 4, the present study has been confined to nozzles with aspect ratio less than 6. In developing the prediction method the essential physics of the problem are taken into consideration. Since the braodband shock associated noise generation mechanism is the same whether the jet is circular or round the present prediction method in a number of ways is quite similar to that for axisymmetric jets. Comparisons between predictions and measurements for jets with aspect ratio up to 6 will be reported. Efforts will be concentrated on the fly-over plane. However, side line angles and other directions will also be included.

  17. A review and update of the NASA aircraft noise prediction program propeller analysis system

    NASA Technical Reports Server (NTRS)

    Golub, Robert A.; Nguyen, L. Cathy

    1989-01-01

    The National Aeronautics and Space Administration (NASA) Aircraft Noise Prediction Program (ANOPP) Propeller Analysis System (PAS) is a set of computational modules for predicting the aerodynamics, performance, and noise of propellers. The ANOPP PAS has the capability to predict noise levels for propeller aircraft certification and produce parametric scaling laws for the adjustment of measured data to reference conditions. A technical overview of the prediction techniques incorporated into the system is presented. The prediction system has been applied to predict the noise signature of a variety of propeller configurations including the effects of propeller angle of attack. A summary of these validation studies is discussed with emphasis being placed on the wind tunnel and flight test programs sponsored by the Federal Aviation Administration (FAA) for the Piper Cherokee Lance aircraft. A number of modifications and improvements have been made to the system and both DEC VAX and IBM-PC versions of the system have been added to the original CDC NOS version.

  18. Prediction of BVI noise patterns and correlation with wake interaction locations

    NASA Technical Reports Server (NTRS)

    Marcolini, Michael A.; Martin, Ruth M.; Lorber, Peter F.; Egolf, T. A.

    1992-01-01

    High resolution fluctuating airloads data were acquired during a test of a contemporary design United Technologies model rotor in the Duits-Nederlandse Windtunnel (DNW). The airloads are used as input to the noise prediction program WOPWOP, in order to predict the blade-vortex interaction (BVI) noise field on a large plane below the rotor. Trends of predicted advancing and retreating side BVI noise levels and directionality as functions of flight condition are presented. The measured airloads have been analyzed to determine the BVI locations on the blade surface, and are used to interpret the predicted BVI noise radiation patterns. Predicted BVI locations are obtained using the free wake model in CAMRAD/JA, the UTRC Generalized Forward Flight Distorted Wake Model, and the UTRC FREEWAKE analysis. These predicted BVI locations are compared with those obtained from the measured pressure data.

  19. A review and update of the NASA aircraft noise prediction program propeller analysis system

    NASA Astrophysics Data System (ADS)

    Golub, Robert A.; Nguyen, L. Cathy

    1989-04-01

    The National Aeronautics and Space Administration (NASA) Aircraft Noise Prediction Program (ANOPP) Propeller Analysis System (PAS) is a set of computational modules for predicting the aerodynamics, performance, and noise of propellers. The ANOPP PAS has the capability to predict noise levels for propeller aircraft certification and produce parametric scaling laws for the adjustment of measured data to reference conditions. A technical overview of the prediction techniques incorporated into the system is presented. The prediction system has been applied to predict the noise signature of a variety of propeller configurations including the effects of propeller angle of attack. A summary of these validation studies is discussed with emphasis being placed on the wind tunnel and flight test programs sponsored by the Federal Aviation Administration (FAA) for the Piper Cherokee Lance aircraft. A number of modifications and improvements have been made to the system and both DEC VAX and IBM-PC versions of the system have been added to the original CDC NOS version.

  20. On Noise Assessment for Blended Wing Body Aircraft

    NASA Technical Reports Server (NTRS)

    Guo, Yueping; Burley, Casey L; Thomas, Russell H.

    2014-01-01

    A system noise study is presented for the blended-wing-body (BWB) aircraft configured with advanced technologies that are projected to be available in the 2025 timeframe of the NASA N+2 definition. This system noise assessment shows that the noise levels of the baseline configuration, measured by the cumulative Effective Perceived Noise Level (EPNL), have a large margin of 34 dB to the aircraft noise regulation of Stage 4. This confirms the acoustic benefits of the BWB shielding of engine noise, as well as other projected noise reduction technologies, but the noise margins are less than previously published assessments and are short of meeting the NASA N+2 noise goal. In establishing the relevance of the acoustic assessment framework, the design of the BWB configuration, the technical approach of the noise analysis, the databases and prediction tools used in the assessment are first described and discussed. The predicted noise levels and the component decomposition are then analyzed to identify the ranking order of importance of various noise components, revealing the prominence of airframe noise, which holds up the levels at all three noise certification locations and renders engine noise reduction technologies less effective. When projected airframe component noise reduction is added to the HWB configuration, it is shown that the cumulative noise margin to Stage 4 can reach 41.6 dB, nearly at the NASA goal. These results are compared with a previous NASA assessment with a different study framework. The approaches that yield projections of such low noise levels are discussed including aggressive assumptions on future technologies, assumptions on flight profile management, engine installation, and component noise reduction technologies. It is shown that reliable predictions of component noise also play an important role in the system noise assessment. The comparisons and discussions illustrate the importance of practical feasibilities and constraints in aircraft

  1. Validation of finite element and boundary element methods for predicting structural vibration and radiated noise

    NASA Technical Reports Server (NTRS)

    Seybert, A. F.; Wu, X. F.; Oswald, Fred B.

    1992-01-01

    Analytical and experimental validation of methods to predict structural vibration and radiated noise are presented. A rectangular box excited by a mechanical shaker was used as a vibrating structure. Combined finite element method (FEM) and boundary element method (BEM) models of the apparatus were used to predict the noise radiated from the box. The FEM was used to predict the vibration, and the surface vibration was used as input to the BEM to predict the sound intensity and sound power. Vibration predicted by the FEM model was validated by experimental modal analysis. Noise predicted by the BEM was validated by sound intensity measurements. Three types of results are presented for the total radiated sound power: (1) sound power predicted by the BEM modeling using vibration data measured on the surface of the box; (2) sound power predicted by the FEM/BEM model; and (3) sound power measured by a sound intensity scan. The sound power predicted from the BEM model using measured vibration data yields an excellent prediction of radiated noise. The sound power predicted by the combined FEM/BEM model also gives a good prediction of radiated noise except for a shift of the natural frequencies that are due to limitations in the FEM model.

  2. “Buzz-saw” noise: Prediction of the rotor-alone pressure field

    NASA Astrophysics Data System (ADS)

    McAlpine, A.; Schwaller, P. J. G.; Fisher, M. J.; Tester, B. J.

    2012-10-01

    Public expectations of lower environmental noise levels, and increasingly stringent legislative limits on aircraft noise, result in noise being a critical technical issue in the development of jet engines. Noise at take-off, when the engines are at high-power operating conditions, is a key reference level for engine noise certification. "Buzz-saw" noise is the dominant fan tone noise from modern high-bypass-ratio turbofan aircraft engines during take-off. Rotor-alone tones are the key component of buzz-saw noise. The rotor-alone pressure field is cut-off at subsonic fan tip speeds; buzz-saw noise is associated with supersonic fan tip speeds, or equivalently, high power engine operating conditions. A recent series of papers has described new work concerning the prediction of buzz-saw noise. The prediction method is based on modelling the nonlinear propagation of one-dimensional sawtooth waveforms. A sawtooth waveform is a simplified representation of the rotor-alone pressure field. Previous validation of the prediction method focussed entirely on reproducing the spectral characteristics of buzz-saw noise; this was dictated at that time by the availability of spectral data only for comparison between measurement and prediction. In this paper, full validation of the method by comparing measurement and prediction of the rotor-alone pressure field is published for the first time. It is shown that results from the modelling based on a one-dimensional sawtooth waveform capture the essential features of the rotor-alone pressure field as it propagates upstream inside a hard-walled inlet duct. This verifies that predictions of the buzz-saw noise spectrum, which are in good agreement with the measured data, are based on a model which reproduces the key physics of the noise generation process. Validation results for the rotor-alone pressure field in an acoustically lined inlet duct are also shown. Comparisons of the measured and predicted rotor-alone pressure field are more

  3. The Prediction of Broadband Shock-Associated Noise from Dualstream and Rectangular Jets Using RANS CFD

    NASA Technical Reports Server (NTRS)

    Miller, Steven A.; Morris, Philip J.

    2010-01-01

    Supersonic jets operating off-design produce broadband shock-associated noise. Broadband shock-associated noise is characterized by multiple broadband peaks in the far-field and is often the dominant source of noise towards the sideline and upstream direction relative to the jet axis. It is due to large scale coherent turbulence structures in the jet shear layers interacting with the shock cell structure. A broadband shock-associated noise model recently developed by the authors predicts this noise component from solutions to the Reynolds averaged Navier-Stokes equations using a two-equation turbulence model. The broadband shock-associated noise model is applied to dualstream and rectangular nozzles operating supersonically, heated, and off-design. The dualstream jet broadband shock-associated noise predictions are conducted for cases when the core jet is supersonic and the fan jet is subsonic, the core jet is subsonic and the fan jet is supersonic, and when both jet streams operate supersonically. Rectangular jet predictions are shown for a convergent-divergent nozzle operating both over- and under-expanded for cold and heated conditions. The original model implementation has been heavily modified to make accurate predictions for the dualstream jets. It is also argued that for over-expanded jets the oblique shock wave attached to the nozzle lip contributes little to broadband shock-associated noise. All predictions are compared with experiments.

  4. A new capability for predicting helicopter rotor and propeller noise including the effect of forward motion

    NASA Technical Reports Server (NTRS)

    Farassat, F.; Brown, T. J.

    1977-01-01

    The governing equation and computing technique for the prediction of helicopter rotor and propeller noise are described. The method which gives both the acoustic pressure time history and spectrum of the noise includes the thickness and the loading noise. It was adapted to computers resulting in a new capability in noise prediction by removing many of the restrictions and limitations of previous theories. The capability results from the fact that the theory is developed entirely in the time domain. The formulation and the technique used are not limited to compact sources, steady level flight or to the far-field. In addition, the inputs to the computer program are normally available or are amenable to experimental measurements. This program can be used to study rotor and propeller noise with the aim of minimizing the radiated noise to reduce annoyance to the public. Several examples demonstrating the features and capability of the computer program are presented.

  5. Slat Noise Simulations: Status and Challenges

    NASA Technical Reports Server (NTRS)

    Choudhari, Meelan M.; Lockhard, David P.; Khorrami, Mehdi R.; Mineck, Raymond E.

    2011-01-01

    Noise radiation from the leading edge slat of a high-lift system is known to be an important component of aircraft noise during approach. NASA's Langley Research Center is engaged in a coordinated series of investigations combining high-fidelity numerical simulations and detailed wind tunnel measurements of a generic, unswept, 3-element, high-lift configuration. The goal of this effort is to provide a validated predictive capability that would enable identification of the dominant noise source mechanisms and, ultimately, help develop physics inspired concepts for reducing the far-field acoustic intensity. This paper provides a brief overview of the current status of the computational effort and describes new findings pertaining to the effects of the angle of attack on the aeroacoustics of the slat cove region. Finally, the interplay of the simulation campaign with the concurrently evolving development of a benchmark dataset for an international workshop on airframe noise is outlined.

  6. Airframe structural optimization for maximum fatigue life

    NASA Technical Reports Server (NTRS)

    Schrage, D. P.; Sareen, A. K.

    1990-01-01

    A methodology is outlined for optimization of airframe structures under dynamic constraints to maximize service life of specified fatigue-critical components. For practical airframe structures, this methodology describes the development of sensitivity analysis and computational procedures for constraints on the steady-state dynamic response displacements and stresses. Strain energy consideration is used for selection of structural members for modification. Development of a design model and its relation to an analysis model, as well as ways to reduce the dimensionality of the problem via approximation concepts, are described. This methodology is demonstrated using an elastic stick model for the MH-53J helicopter to show service life improvements of the hinge fold region.

  7. Psychoacoustic Analysis of Synthesized Jet Noise

    NASA Technical Reports Server (NTRS)

    Okcu, Selen; Rathsam, Jonathan; Rizzi, Stephen A.

    2013-01-01

    An aircraft noise synthesis capability is being developed so the annoyance caused by proposed aircraft can be assessed during the design stage. To make synthesized signals as realistic as possible, high fidelity simulation is required for source (e.g., engine noise, airframe noise), propagation and receiver effects. This psychoacoustic study tests whether the jet noise component of synthesized aircraft engine noise can be made more realistic using a low frequency oscillator (LFO) technique to simulate fluctuations in level observed in recordings. Jet noise predictions are commonly made in the frequency domain based on models of time-averaged empirical data. The synthesis process involves conversion of the frequency domain prediction into an audible pressure time history. However, because the predictions are time-invariant, the synthesized sound lacks fluctuations observed in recordings. Such fluctuations are hypothesized to be perceptually important. To introduce time-varying characteristics into jet noise synthesis, a method has been developed that modulates measured or predicted 1/3-octave band levels with a (<20Hz) LFO. The LFO characteristics are determined through analysis of laboratory jet noise recordings. For the aft emission angle, results indicate that signals synthesized using a generic LFO are perceived as more similar to recordings than those using no LFO, and signals synthesized with an angle-specific LFO are more similar to recordings than those synthesized with a generic LFO.

  8. The Uses and Abuses of the Acoustic Analogy in Helicopter Rotor Noise Prediction

    NASA Technical Reports Server (NTRS)

    Farassat, F.; Brentner, Kenneth S.

    1987-01-01

    This paper is theoretical in nature and addresses applications of the acoustic analogy in helicopter rotor noise prediction. It is argued that in many instances the acoustic analogy has not been used with care in rotor noise studies. By this it is meant that approximate or inappropriate formulations have been used. By considering various mechanisms of noise generation, such abuses are identified and the remedy is suggested. The mechanisms discussed are thickness, loading, quadrupole, and blade-vortex interaction noise. The quadrupole term of the Ffowcs Williams-Hawkings equation is written in a new form which separates the contributions of regions of high gradients such as shock surfaces. It is shown by order of magnitude studies that such regions are capable of producing noise with the same directivity as the thickness noise. The inclusion of this part of quadrupole sources in current acoustic codes is quite practical. Some of the difficulties with the use of loading noise formulations of the first author in predictions of blade-vortex interaction noise are discussed. It appears that there is a need for development of new theoretical results based on the acoustic analogy in this area. Because of the impulsive character of the blade surface pressure, a time scale of integration different from that used in loading and thickness computations must he used in a computer code for prediction of blade-vortex interaction noise.

  9. A human-hearing-related prediction tool for soundscapes and community noise

    NASA Astrophysics Data System (ADS)

    Genuit, Klaus

    2002-11-01

    There are several methods of calculation available for the prediction of the A-weighted sound-pressure level of environmental noise, which are, however, not suitable for a qualified prediction of the residents' annoyance and physiological strain. The subjectively felt noise quality does not only depend on the A-weighted sound-pressure level, but also on other psychoacoustical parameters, such as loudness, roughness, sharpness, etc. In addition to these physical and psychoacoustical aspects of noise, the so-called psychological or cognitive aspects have to be considered, too, which means that the listeners' expectations, their mental attitude, as well as the information content of the noise finally influence the noise quality perceived by the individual persons. Within the scope of a research project SVEN (Sound Quality of Vehicle Exterior Noise), which is promoted by the EC, a new tool has been developed which allows a binaural simulation and prediction of the environmental noise to evaluate the influence of different contributions by the sound events with respect to the psychoacoustical parameters, the spatial distribution, movement, and frequency. By means of this tool it is now possible to consider completely new aspects regarding the audible perception of noise when establishing a soundscape or when planning community noise.

  10. Auralization of NASA N+2 Aircraft Concepts from System Noise Predictions

    NASA Technical Reports Server (NTRS)

    Rizzi, Stephen A.; Burley, Casey L.; Thomas, Russel H.

    2016-01-01

    Auralization of aircraft flyover noise provides an auditory experience that complements integrated metrics obtained from system noise predictions. Recent efforts have focused on auralization methods development, specifically the process by which source noise information obtained from semi-empirical models, computational aeroacoustic analyses, and wind tunnel and flight test data, are used for simulated flyover noise at a receiver on the ground. The primary focus of this work, however, is to develop full vehicle auralizations in order to explore the distinguishing features of NASA's N+2 aircraft vis-à-vis current fleet reference vehicles for single-aisle and large twin-aisle classes. Some features can be seen in metric time histories associated with aircraft noise certification, e.g., tone-corrected perceived noise level used in the calculation of effective perceived noise level. Other features can be observed in sound quality metrics, e.g., loudness, sharpness, roughness, fluctuation strength and tone-to-noise ratio. A psychoacoustic annoyance model is employed to establish the relationship between sound quality metrics and noise certification metrics. Finally, the auralizations will serve as the basis for a separate psychoacoustic study aimed at assessing how well aircraft noise certification metrics predict human annoyance for these advanced vehicle concepts.

  11. Relationship between Aircraft Noise Contour Area and Noise Levels at Certification Points

    NASA Technical Reports Server (NTRS)

    Powell, Clemans A.

    2003-01-01

    The use of sound exposure level contour area reduction has been proposed as an alternative or supplemental metric of progress and success for the NASA Quiet Aircraft Technology program, which currently uses the average of predicted noise reductions at three community locations. As the program has expanded to include reductions in airframe noise as well as reduction due to optimization of operating procedures for lower noise, there is concern that the three-point methodology may not represent a fair measure of benefit to airport communities. This paper addresses several topics related to this proposal: (1) an analytical basis for a relationship between certification noise levels and noise contour areas for departure operations is developed, (2) the relationship between predicted noise contour area and the noise levels measured or predicted at the certification measurement points is examined for a wide range of commercial and business aircraft, and (3) reductions in contour area for low-noise approach scenarios are predicted and equivalent reductions in source noise are determined.

  12. Evaluation of Turbulence-Model Performance as Applied to Jet-Noise Prediction

    NASA Technical Reports Server (NTRS)

    Woodruff, S. L.; Seiner, J. M.; Hussaini, M. Y.; Erlebacher, G.

    1998-01-01

    The accurate prediction of jet noise is possible only if the jet flow field can be predicted accurately. Predictions for the mean velocity and turbulence quantities in the jet flowfield are typically the product of a Reynolds-averaged Navier-Stokes solver coupled with a turbulence model. To evaluate the effectiveness of solvers and turbulence models in predicting those quantities most important to jet noise prediction, two CFD codes and several turbulence models were applied to a jet configuration over a range of jet temperatures for which experimental data is available.

  13. Trailing edge noise prediction from measured surface pressures

    NASA Technical Reports Server (NTRS)

    Brooks, T. F.; Hodgson, T. H.

    1981-01-01

    Trailing edge (TE) noise is investigated for the case of a two-dimensional airfoil embedded in a uniform low Mach number flow, and the usefulness of several TE noise theories is examined by applying them to the measured data. The TE noise spectra and directivity are quantitatively determined for the case of a high Reynolds number and a fully turbulent boundary layer. Parameters include angle of attack, flow velocity and TE bluntness. Evanescent wave theories by Chase (1975) and Chandiramani (1974) are compared to the present results and show good agreement. Agreement of the near field pressure scatter phenomenon analysis with measurements implies that the basic assumptions used in the analysis are correct, i.e., the turbulent boundary layer (TBL) flow passes the trailing edge into the wake region. No hydrodynamic wake shedding activity is confirmed for the two-sided TBL flow, and a method incorporating the principles of the coherent output power method is used to determine the sound field. The near field edge scatter model is found to not only establish optimum sizing of edge treatment for noise control, but also to separate and identify the scattered field from the incident hydrodynamic field.

  14. Structural Qualification of Composite Airframes

    NASA Technical Reports Server (NTRS)

    Kedward, Keith T.; McCarty, John E.

    1997-01-01

    The development of fundamental approaches for predicting failure and elongation characteristics of fibrous composites are summarized in this document. The research described includes a statistical formulation for individual fiber breakage and fragmentation and clustered fiber breakage, termed macrodefects wherein the aligned composite may represent a structural component such as a reinforcing bar element, a rebar. Experimental work conducted in support of the future exploitation of aligned composite rebar elements is also described. This work discusses the experimental challenges associated with rebar tensile test evaluation and describes initial numerical analyses performed in support of the experimental program.

  15. Design of the Next Generation Aircraft Noise Prediction Program: ANOPP2

    NASA Technical Reports Server (NTRS)

    Lopes, Leonard V., Dr.; Burley, Casey L.

    2011-01-01

    The requirements, constraints, and design of NASA's next generation Aircraft NOise Prediction Program (ANOPP2) are introduced. Similar to its predecessor (ANOPP), ANOPP2 provides the U.S. Government with an independent aircraft system noise prediction capability that can be used as a stand-alone program or within larger trade studies that include performance, emissions, and fuel burn. The ANOPP2 framework is designed to facilitate the combination of acoustic approaches of varying fidelity for the analysis of noise from conventional and unconventional aircraft. ANOPP2 integrates noise prediction and propagation methods, including those found in ANOPP, into a unified system that is compatible for use within general aircraft analysis software. The design of the system is described in terms of its functionality and capability to perform predictions accounting for distributed sources, installation effects, and propagation through a non-uniform atmosphere including refraction and the influence of terrain. The philosophy of mixed fidelity noise prediction through the use of nested Ffowcs Williams and Hawkings surfaces is presented and specific issues associated with its implementation are identified. Demonstrations for a conventional twin-aisle and an unconventional hybrid wing body aircraft configuration are presented to show the feasibility and capabilities of the system. Isolated model-scale jet noise predictions are also presented using high-fidelity and reduced order models, further demonstrating ANOPP2's ability to provide predictions for model-scale test configurations.

  16. Prediction of broadband noise from large horizontal axis wind turbine generators

    NASA Technical Reports Server (NTRS)

    Grosveld, F. W.

    1984-01-01

    A method is presented for predicting the broadband noise spectra of large horizontal axis wind turbine generators. It includes contributions from such noise sources as the inflow turbulence to the rotor, the interactions between the turbulent boundary layers on the blade surfaces with their trailing edges and the wake due to a blunt trailing edge. The method is partly empirical and is based on acoustic measurements of large wind turbines and airfoil models. The predicted frequency spectra are compared with measured data from several machines including the MOD-OA, the MOD-2, the WTS-4 and the U.S. Wind-power Inc. machine. Also included is a broadband noise prediction for the proposed MOD-5B. The significance of the effects of machine size, power output, trailing edge bluntness and distance to the receiver is illustrated. Good agreement is obtained between the predicted and measured far field noise spectra.

  17. Small Engine Technology (SET) Task 23 ANOPP Noise Prediction for Small Engines, Wing Reflection Code

    NASA Technical Reports Server (NTRS)

    Lieber, Lysbeth; Brown, Daniel; Golub, Robert A. (Technical Monitor)

    2000-01-01

    The work performed under Task 23 consisted of the development and demonstration of improvements for the NASA Aircraft Noise Prediction Program (ANOPP), specifically targeted to the modeling of engine noise enhancement due to wing reflection. This report focuses on development of the model and procedure to predict the effects of wing reflection, and the demonstration of the procedure, using a representative wing/engine configuration.

  18. On the prediction of impact noise, Part IX: The noise from punch presses

    NASA Astrophysics Data System (ADS)

    Richards, E. J.; Stimpson, G. J.

    1985-11-01

    The punch press is a further classical example of impact noise: the force is built up in the punch relatively slowly, and the whole machine is strained until the load on the material being punched reaches a yield and shortly afterwards a fracture level. At this stage the strain energy in the machine and its workpiece must be redistributed and this leads to vibration of the whole machine and to noise radiation. In this paper work which has been carried out at ISVR over a number of years is presented. It describes the way the Energy Accountancy Equation [1] can be modified to relate the noise radiated directly to the sum of the squares of the large rates of change of force against time, and illustrates clearly the way that noise control, with use of passive or active methods in designing the punch tooling, can be related directly to the one parameter 10 log Σ[ f( t)] max2. It is shown that noise levels can be reduced by up to 30 dB under ideal conditions by fracture pulse tailoring while still cutting metal, but that more realistically, 10 dB reductions may be obtained below those of current practice by practical tool design. An explanation is given of why large open presses are never likely to achieve the proposed factory noise levels and that the noise from double-sided presses can be controlled effectively by tooling modifications and by the addition of damping. The paper describes work carried out on passive and active cancellation systems used to arrest and springback of the press structure following workpiece material fracture and explains the practical limitations of such systems. Active techniques are limited by the difficulties obtained, with brittle hard materials, of finding a trigger and load freezing system which can operate fast enough to reduce adequately the force parameter 10 log Σ ( fmax( t)) 2. Where punching finish allows, it has been found that well-designed shear and/or cutting with low percentage clearance is superior to active cancellation

  19. Interior noise control prediction study for high-speed propeller-driven aircraft

    NASA Technical Reports Server (NTRS)

    Rennison, D. C.; Wilby, J. F.; Marsh, A. H.; Wilby, E. G.

    1979-01-01

    An analytical model was developed to predict the noise levels inside propeller-driven aircraft during cruise at M = 0.8. The model was applied to three study aircraft with fuselages of different size (wide body, narrow body and small diameter) in order to determine the noise reductions required to achieve the goal of an A-weighted sound level which does not exceed 80 dB. The model was then used to determine noise control methods which could achieve the required noise reductions. Two classes of noise control treatments were investigated: add-on treatments which can be added to existing structures, and advanced concepts which would require changes to the fuselage primary structure. Only one treatment, a double wall with limp panel, provided the required noise reductions. Weight penalties associated with the treatment were estimated for the three study aircraft.

  20. Methods for Predicting Potential Impacts of Pile-Driving Noise on Endangered Sturgeon During Bridge Construction.

    PubMed

    Krebs, Justin; Jacobs, Fred; Conway, Robert; Popper, Arthur N; Moese, Mark; Rollino, John; Racca, Roberto; Martin, Bruce; MacGillivray, Alexander

    2016-01-01

    The potential impacts of pile-driving noise on Hudson River sturgeon during construction of the New NY Bridge were predicted. Abundance data for shortnose and Atlantic sturgeon derived from fisheries sampling were combined with data about the spatial extent of pile-driving noise. This approach was used to calculate the number of sturgeon that could occur within sound level isopleths exceeding peak and cumulative noise criteria used by the National Marine Fisheries Service to determine the incidental take of sturgeon. The number of sturgeon subject to the potential onset of physiological effects during pile driving was predicted to be 35-41 fish for each species.

  1. Application of a pattern recognition technique to the prediction of tire noise

    NASA Astrophysics Data System (ADS)

    Chiu, Jinn-Tong; Tu, Fu-Yuan

    2015-08-01

    Tire treads are one of the main sources of car noise. To meet the EU's tire noise regulation ECE-R117, a new method using a pattern recognition technique is adopted in this paper to predict noise from tire tread patterns, thus facilitating the design of low-noise tires. When tires come into contact with the road surface, air pumping may occur in the grooves of tire tread patterns. Using the image of a tread pattern, a matrix is constructed by setting the patterns of tire grooves and tread blocks. The length and width of the contact patch are multiplied by weight functions. The resulting sound pressure as a function of time is subjected to a Fourier transform to simulate a 1/3-octave-band sound pressure level. A particle swarm algorithm is adopted to optimize the weighting parameters for the sound pressure in the frequency domain so that simulated values approach the measured noise level. Two sets of optimal weighting parameters associated with the length and width of the contact patch are obtained. Finally, the weight function is used to predict the tread pattern noise of tires in the same series. A comparison of the prediction and experimental results reveals that, in the 1/3-octave band of frequency (800-2000 Hz), average errors in sound pressure are within 2.5 dB. The feasibility of the proposed application of the pattern recognition technique in predicting noise from tire treads is verified.

  2. Analysis of impact/impulse noise for predicting noise induced hearing loss

    NASA Astrophysics Data System (ADS)

    Vipperman, Jeffrey S.; Prince, Mary M.; Flamm, Angela M.

    2003-04-01

    Studies indicate that the statistical properties and temporal structure of the sound signal are important in determining the extent of hearing hazard. As part of a pilot study to examine hearing conservation program effectiveness, NIOSH collected noise samples of impact noise sources in an automobile stamping plant, focusing on jobs with peak sound levels (Lpk) of greater than 120 dB. Digital tape recordings of sounds were collected using a Type I Precision Sound Level Meter and microphone connected to a DAT tape recorder. The events were archived and processed as .wav files to extract single events of interest on CD-R media and CD audio media. A preliminary analysis of sample wavelet files was conducted to characterize each event using metrics such as the number of impulses per unit time, the repetition rate or temporal pattern of these impulses, index of peakedness, crest factor, kurtosis, coefficient of kurtosis, rise time, fall time, and peak time. The spectrum, duration, and inverse of duration for each waveform were also computed. Finally, the data were evaluated with the Auditory Hazard Assessment Algorithm (AHAAH). Improvements to data collection for a future study examining different strategies for evaluating industrial noise exposure will be discussed.

  3. Perpendicular blade vortex interaction and its implications for helicopter noise prediction: Wave-number frequency spectra in a trailing vortex for BWI noise prediction

    NASA Technical Reports Server (NTRS)

    Devenport, William J.; Glegg, Stewart A. L.

    1993-01-01

    Perpendicular blade vortex interactions are a common occurrence in helicopter rotor flows. Under certain conditions they produce a substantial proportion of the acoustic noise. However, the mechanism of noise generation is not well understood. Specifically, turbulence associated with the trailing vortices shed from the blade tips appears insufficient to account for the noise generated. The hypothesis that the first perpendicular interaction experienced by a trailing vortex alters its turbulence structure in such a way as to increase the acoustic noise generated by subsequent interactions is examined. To investigate this hypothesis a two-part investigation was carried out. In the first part, experiments were performed to examine the behavior of a streamwise vortex as it passed over and downstream of a spanwise blade in incompressible flow. Blade vortex separations between +/- one eighth chord were studied for at a chord Reynolds number of 200,000. Three-component velocity and turbulence measurements were made in the flow from 4 chord lengths upstream to 15 chordlengths downstream of the blade using miniature 4-sensor hot wire probes. These measurements show that the interaction of the vortex with the blade and its wake causes the vortex core to loose circulation and diffuse much more rapidly than it otherwise would. Core radius increases and peak tangential velocity decreases with distance downstream of the blade. True turbulence levels within the core are much larger downstream than upstream of the blade. The net result is a much larger and more intense region of turbulent flow than that presented by the original vortex and thus, by implication, a greater potential for generating acoustic noise. In the second part, the turbulence measurements described above were used to derive the necessary inputs to a Blade Wake Interaction (BWI) noise prediction scheme. This resulted in significantly improved agreement between measurements and calculations of the BWI noise

  4. Reducing Propulsion Airframe Aeroacoustic Interactions With Uniquely Tailored Chevrons: 3. Jet-Flap Interaction

    NASA Technical Reports Server (NTRS)

    Thomas, Russ H.; Mengle, Vinod G.; Brunsniak, Leon; Elkoby, Ronen

    2006-01-01

    Propulsion airframe aeroacoustic (PAA) interactions, resulting from the integration of engine and airframe, lead to azimuthal asymmetries in the flow/acoustic field, e.g., due to the interaction between the exhaust jet flow and the pylon, the wing and its high-lift devices, such as, flaps and flaperons. In the first two parts of this series we have presented experimental results which show that isolated and installed nozzles with azimuthally varying chevrons (AVCs) can reduce noise more than conventional chevrons when integrated with a pylon and a wing with flaps at take-off conditions. In this paper, we present model-scale experimental results for the reduction of jet-flap interaction noise source due to these AVCs and document the PAA installation effects (difference in noise between installed and isolated nozzle configurations) at both approach and take-off conditions. It is found that the installation effects of both types of chevron nozzles, AVCs and conventional, are reversed at approach and take-off, in that there is more installed noise reduction at approach and less at take-off compared to that of the isolated nozzles. Moreover, certain AVCs give larger total installed noise benefits at both conditions compared to conventional chevrons. Phased microphone array results show that at approach conditions (large flap deflection, low jet speed and low ambient Mach number), chevrons gain more noise benefit from reducing jetflap interaction noise than they do from quieting the jet plume noise source which is already weak at these low jet speeds. In contrast, at take-off (small flap deflection, high jet speed and high ambient Mach number) chevrons reduce the dominant jet plume noise better than the reduction they create in jet-flap interaction noise source. In addition, fan AVCs with enhanced mixing near the pylon are found to reduce jet-flap interaction noise better than conventional chevrons at take-off.

  5. AH-1G flight vibration correlation using NASTRAN and the C81 rotor/airframe coupled analysis

    NASA Technical Reports Server (NTRS)

    Dompka, R. V.; Corrigan, J. J.

    1986-01-01

    Analytical results are presented bearing on the accuracy of state-of-the-art NASTRAN FEM modeling techniques and rotor/airframe coupling methods for the prediction of flight vibrations; these results have been studied by NASA and industry experts in order to ensure scientific control of the analysis/correlation exercise. The rotor loads predicted by the dynamically coupled rotor/airframe analysis showed good agreement between calculated and experimental blade loads, as did the predominant excitation frequency vibration levels predicted by NASTRAN.

  6. Airframe Technology Development for Next Generation Launch Vehicles

    NASA Technical Reports Server (NTRS)

    Glass, David E.

    2004-01-01

    The Airframe subproject within NASA's Next Generation Launch Technology (NGLT) program has the responsibility to develop airframe technology for both rocket and airbreathing vehicles for access to space. The Airframe sub-project pushes the state-of-the-art in airframe technology for low-cost, reliable, and safe space transportation. Both low and medium technology readiness level (TRL) activities are being pursued. The key technical areas being addressed include design and integration, hot and integrated structures, cryogenic tanks, and thermal protection systems. Each of the technologies in these areas are discussed in this paper.

  7. Development of a traffic noise prediction model on inland waterway of China using the FHWA.

    PubMed

    Dai, Ben-lin; He, Yu-long; Mu, Fei-hu; Xu, Ning; Wu, Zhen

    2014-06-01

    Based on the local environmental standards, vessels types and traffic conditions, an inland waterway traffic noise prediction model was developed for use in China. This model was modified from the US FHWA model by adding the ground absorption and water surface attenuation correction terms to the governing equations. The parameters that were input into the equations, including traffic flow, vessel speed, distance from the center of the inland waterway to the receiver, position and height of the barriers and buildings, location of the receiver, type of ground, percentage of soft ground cover within the segment, and water surface conditions were re-defined. The model was validated by comparing the measured noise levels obtained at 33 sampling sites from Shugang Channel, Yanhe Channel and Danjinlicaohe Channel in China with the predicted values. The deviation between the predicted and measured noise levels within the range of ±1.5dB(A) was 81.8%. The mean difference between the predicted and measured noise levels was 0.15±1.75dB(A). However, the noise levels predicted developed model are generally higher than the measured levels. Overall, the comparison has proved that the developed method is of a high precision, and that it can be applied to estimate the traffic noise exposure level on inland waterway in China.

  8. The Acoustic Analogy: A Powerful Tool in Aeroacoustics with Emphasis on Jet Noise Prediction

    NASA Technical Reports Server (NTRS)

    Farassat, F.; Doty, Michael J.; Hunter, Craig A.

    2004-01-01

    The acoustic analogy introduced by Lighthill to study jet noise is now over 50 years old. In the present paper, Lighthill s Acoustic Analogy is revisited together with a brief evaluation of the state-of-the-art of the subject and an exploration of the possibility of further improvements in jet noise prediction from analytical methods, computational fluid dynamics (CFD) predictions, and measurement techniques. Experimental Particle Image Velocimetry (PIV) data is used both to evaluate turbulent statistics from Reynolds-averaged Navier-Stokes (RANS) CFD and to propose correlation models for the Lighthill stress tensor. The NASA Langley Jet3D code is used to study the effect of these models on jet noise prediction. From the analytical investigation, a retarded time correction is shown that improves, by approximately 8 dB, the over-prediction of aft-arc jet noise by Jet3D. In experimental investigation, the PIV data agree well with the CFD mean flow predictions, with room for improvement in Reynolds stress predictions. Initial modifications, suggested by the PIV data, to the form of the Jet3D correlation model showed no noticeable improvements in jet noise prediction.

  9. Development and Validation of a Multidisciplinary Tool for Accurate and Efficient Rotorcraft Noise Prediction (MUTE)

    NASA Technical Reports Server (NTRS)

    Liu, Yi; Anusonti-Inthra, Phuriwat; Diskin, Boris

    2011-01-01

    A physics-based, systematically coupled, multidisciplinary prediction tool (MUTE) for rotorcraft noise was developed and validated with a wide range of flight configurations and conditions. MUTE is an aggregation of multidisciplinary computational tools that accurately and efficiently model the physics of the source of rotorcraft noise, and predict the noise at far-field observer locations. It uses systematic coupling approaches among multiple disciplines including Computational Fluid Dynamics (CFD), Computational Structural Dynamics (CSD), and high fidelity acoustics. Within MUTE, advanced high-order CFD tools are used around the rotor blade to predict the transonic flow (shock wave) effects, which generate the high-speed impulsive noise. Predictions of the blade-vortex interaction noise in low speed flight are also improved by using the Particle Vortex Transport Method (PVTM), which preserves the wake flow details required for blade/wake and fuselage/wake interactions. The accuracy of the source noise prediction is further improved by utilizing a coupling approach between CFD and CSD, so that the effects of key structural dynamics, elastic blade deformations, and trim solutions are correctly represented in the analysis. The blade loading information and/or the flow field parameters around the rotor blade predicted by the CFD/CSD coupling approach are used to predict the acoustic signatures at far-field observer locations with a high-fidelity noise propagation code (WOPWOP3). The predicted results from the MUTE tool for rotor blade aerodynamic loading and far-field acoustic signatures are compared and validated with a variation of experimental data sets, such as UH60-A data, DNW test data and HART II test data.

  10. Improved NASA-ANOPP Noise Prediction Computer Code for Advanced Subsonic Propulsion Systems. Volume 2; Fan Suppression Model Development

    NASA Technical Reports Server (NTRS)

    Kontos, Karen B.; Kraft, Robert E.; Gliebe, Philip R.

    1996-01-01

    The Aircraft Noise Predication Program (ANOPP) is an industry-wide tool used to predict turbofan engine flyover noise in system noise optimization studies. Its goal is to provide the best currently available methods for source noise prediction. As part of a program to improve the Heidmann fan noise model, models for fan inlet and fan exhaust noise suppression estimation that are based on simple engine and acoustic geometry inputs have been developed. The models can be used to predict sound power level suppression and sound pressure level suppression at a position specified relative to the engine inlet.

  11. Broadband Fan Noise Prediction System for Turbofan Engines. Volume 3; Validation and Test Cases

    NASA Technical Reports Server (NTRS)

    Morin, Bruce L.

    2010-01-01

    Pratt & Whitney has developed a Broadband Fan Noise Prediction System (BFaNS) for turbofan engines. This system computes the noise generated by turbulence impinging on the leading edges of the fan and fan exit guide vane, and noise generated by boundary-layer turbulence passing over the fan trailing edge. BFaNS has been validated on three fan rigs that were tested during the NASA Advanced Subsonic Technology Program (AST). The predicted noise spectra agreed well with measured data. The predicted effects of fan speed, vane count, and vane sweep also agreed well with measurements. The noise prediction system consists of two computer programs: Setup_BFaNS and BFaNS. Setup_BFaNS converts user-specified geometry and flow-field information into a BFaNS input file. From this input file, BFaNS computes the inlet and aft broadband sound power spectra generated by the fan and FEGV. The output file from BFaNS contains the inlet, aft and total sound power spectra from each noise source. This report is the third volume of a three-volume set documenting the Broadband Fan Noise Prediction System: Volume 1: Setup_BFaNS User s Manual and Developer s Guide; Volume 2: BFaNS User s Manual and Developer s Guide; and Volume 3: Validation and Test Cases. The present volume begins with an overview of the Broadband Fan Noise Prediction System, followed by validation studies that were done on three fan rigs. It concludes with recommended improvements and additional studies for BFaNS.

  12. Aviation Maintenance Technology. Airframe. A201. Airframe Structures and Non-Metallic Structural Repairs. Instructor Material.

    ERIC Educational Resources Information Center

    Oklahoma State Board of Vocational and Technical Education, Stillwater. Curriculum and Instructional Materials Center.

    This teacher's guide is designed to aid teachers in leading students through a module on airframe structures and nonmetallic structural repairs. The module contains four units that cover the following topics: (1) identifying aerodynamic and construction characteristics of aircraft structures; (2) inspecting wooden structures; (3) inspecting and…

  13. Development of an Empirical Methods for Predicting Jet Mixing Noise of Cold Flow Rectangular Jets

    NASA Technical Reports Server (NTRS)

    Russell, James W.

    1999-01-01

    This report presents an empirical method for predicting the jet mixing noise levels of cold flow rectangular jets. The report presents a detailed analysis of the methodology used in development of the prediction method. The empirical correlations used are based on narrow band acoustic data for cold flow rectangular model nozzle tests conducted in the NASA Langley Jet Noise Laboratory. There were 20 separate nozzle test operating conditions. For each operating condition 60 Hz bandwidth microphone measurements were made over a frequency range from 0 to 60,000 Hz. Measurements were performed at 16 polar directivity angles ranging from 45 degrees to 157.5 degrees. At each polar directivity angle, measurements were made at 9 azimuth directivity angles. The report shows the methods employed to remove screech tones and shock noise from the data in order to obtain the jet mixing noise component. The jet mixing noise was defined in terms of one third octave band spectral content, polar and azimuth directivity, and overall power level. Empirical correlations were performed over the range of test conditions to define each of these jet mixing noise parameters as a function of aspect ratio, jet velocity, and polar and azimuth directivity angles. The report presents the method for predicting the overall power level, the average polar directivity, the azimuth directivity and the location and shape of the spectra for jet mixing noise of cold flow rectangular jets.

  14. Auditory brainstem measures predict reading and speech-in-noise perception in school-aged children.

    PubMed

    Hornickel, Jane; Chandrasekaran, Bharath; Zecker, Steve; Kraus, Nina

    2011-01-20

    Reading and speech-in-noise perception, fundamental aspects of human communication, have been linked to neural indices of auditory brainstem function. However, how these factors interact is currently unclear. Multivariate analysis methods (structural equation modeling) were employed to delineate and quantify the relationships among factors that relate to successful reading and speech in noise perception in children. Neural measures of subcortical speech encoding that reflect the utilization of stimulus regularities, differentiation of stop consonants, and robustness of neural synchrony predicted 73% of the variance in reading scores. A different combination of neural measures, specifically, utilization of stimulus regularities, strength of encoding of lower harmonics, and the extent of noise-induced timing delays uniquely predicted 56% of the variance in speech-in-noise perception measures. The neural measures relating to reading and speech-in-noise perception were substantially non-overlapping and resulted in poor fitting models when substituted for each other, thereby suggesting distinct neural signatures for the two skills. When phonological processing and working memory measures were added to the models, brainstem measures still uniquely predicted variance in reading ability and speech-in-noise perception, highlighting the robustness of the relationship between subcortical auditory function and these skills. The current study suggests that objective neural markers may prove valuable in the assessment of reading or speech-in-noise abilities in children.

  15. Corrosion and corrosion fatigue of airframe aluminum alloys

    NASA Technical Reports Server (NTRS)

    Chen, G. S.; Gao, M.; Harlow, D. G.; Wei, R. P.

    1994-01-01

    Localized corrosion and corrosion fatigue crack nucleation and growth are recognized as degradation mechanisms that effect the durability and integrity of commercial transport aircraft. Mechanically based understanding is needed to aid the development of effective methodologies for assessing durability and integrity of airframe components. As a part of the methodology development, experiments on pitting corrosion, and on corrosion fatigue crack nucleation and early growth from these pits were conducted. Pitting was found to be associated with constituent particles in the alloys and pit growth often involved coalescence of individual particle-nucleated pits, both laterally and in depth. Fatigue cracks typically nucleated from one of the larger pits that formed by a cluster of particles. The size of pit at which fatigue crack nucleates is a function of stress level and fatigue loading frequency. The experimental results are summarized, and their implications on service performance and life prediction are discussed.

  16. Fuel efficiency through new airframe technology

    NASA Technical Reports Server (NTRS)

    Leonard, R. W.

    1982-01-01

    In its Aircraft Energy Efficiency Program, NASA has expended approximately 200 million dollars toward development and application of advanced airframe technologies to United States's commercial transports. United States manufacturers have already been given a significant boost toward early application of advanced composite materials to control surface and empennage structures and toward selected applications of active controls and advanced aerodynamic concepts. In addition, significant progress in definition and development of innovative, but realistic systems for laminar flow control over the wings of future transports has already been made.

  17. Optimal airframe synthesis for gust loads

    NASA Technical Reports Server (NTRS)

    Hajela, P.

    1986-01-01

    An optimization capability for sizing airframe structures that are subjected to a combination of deterministic and random flight loads was established. The random vibration environment introduces the need for selecting a statistical process that best describes the random loads and permits computation of the dynamic response parameters of interest. Furthermore, it requires a formulation of design constraints that would minimize the conservativeness in the design and retain computational viability. The random loads are treated as a stationary, homogeneous process with a Gaussian probability distribution. The formulation of the analysis problem, the structure of the optimization programming system and a representative numerical example are discussed.

  18. Frequency-space prediction filtering for acoustic clutter and random noise attenuation in ultrasound imaging

    NASA Astrophysics Data System (ADS)

    Shin, Junseob; Huang, Lianjie

    2016-04-01

    Frequency-space prediction filtering (FXPF), also known as FX deconvolution, is a technique originally developed for random noise attenuation in seismic imaging. FXPF attempts to reduce random noise in seismic data by modeling only real signals that appear as linear or quasilinear events in the aperture domain. In medical ultrasound imaging, channel radio frequency (RF) signals from the main lobe appear as horizontal events after receive delays are applied while acoustic clutter signals from off-axis scatterers and electronic noise do not. Therefore, FXPF is suitable for preserving only the main-lobe signals and attenuating the unwanted contributions from clutter and random noise in medical ultrasound imaging. We adapt FXPF to ultrasound imaging, and evaluate its performance using simulated data sets from a point target and an anechoic cyst. Our simulation results show that using only 5 iterations of FXPF achieves contrast-to-noise ratio (CNR) improvements of 67 % in a simulated noise-free anechoic cyst and 228 % in a simulated anechoic cyst contaminated with random noise of 15 dB signal-to-noise ratio (SNR). Our findings suggest that ultrasound imaging with FXPF attenuates contributions from both acoustic clutter and random noise and therefore, FXPF has great potential to improve ultrasound image contrast for better visualization of important anatomical structures and detection of diseased conditions.

  19. Prediction of noise levels and annoyance from aircraft run-ups at Vancouver International Airport.

    PubMed

    Scherebnyj, Katrina; Hodgson, Murray

    2007-10-01

    Annoyance complaints resulting from engine run-ups have been increasing at Vancouver International Airport for several years. To assist the Airport in managing run-up noise levels, a prediction tool based on a Green's function parabolic equation (GFPE) model has been consolidated, evaluated, and applied. It was extended to include more realistic atmospheric and ground input parameters. Measurements were made of the noise-radiation characteristics of a CRJ200 jet aircraft. The GFPE model was validated by comparing predictions with results in the literature. A sensitivity analysis showed that predicted levels are relatively insensitive to small variations in geometry and ground impedance, but relatively sensitive to variations in wind speed, atmosphere type, and aircraft heading and power setting. Predicted noise levels were compared with levels measured at noise monitoring terminals. For the four cases for which all input information was available, agreement was within 10 dBA. For events for which some information had to be estimated, predictions were within 20 dBA. The predicted annoyance corresponding to the run-up events considered ranged from 1.8% to 9.5% of people awoken, suggesting that noise complaints can be expected.

  20. A noise level prediction method based on electro-mechanical frequency response function for capacitors.

    PubMed

    Zhu, Lingyu; Ji, Shengchang; Shen, Qi; Liu, Yuan; Li, Jinyu; Liu, Hao

    2013-01-01

    The capacitors in high-voltage direct-current (HVDC) converter stations radiate a lot of audible noise which can reach higher than 100 dB. The existing noise level prediction methods are not satisfying enough. In this paper, a new noise level prediction method is proposed based on a frequency response function considering both electrical and mechanical characteristics of capacitors. The electro-mechanical frequency response function (EMFRF) is defined as the frequency domain quotient of the vibration response and the squared capacitor voltage, and it is obtained from impulse current experiment. Under given excitations, the vibration response of the capacitor tank is the product of EMFRF and the square of the given capacitor voltage in frequency domain, and the radiated audible noise is calculated by structure acoustic coupling formulas. The noise level under the same excitations is also measured in laboratory, and the results are compared with the prediction. The comparison proves that the noise prediction method is effective. PMID:24349105

  1. Comparison of Transmission Error Predictions with Noise Measurements for Several Spur and Helical Gears

    NASA Technical Reports Server (NTRS)

    Houser, Donald R.; Oswald, Fred B.; Valco, Mark J.; Drago, Raymond J.; Lenski, Joseph W., Jr.

    1994-01-01

    Measured sound power data from eight different spur, single and double helical gear designs are compared with predictions of transmission error by the Load Distribution Program. The sound power data was taken from the recent Army-funded Advanced Rotorcraft Transmission project. Tests were conducted in the NASA gear noise rig. Results of both test data and transmission error predictions are made for each harmonic of mesh frequency at several operating conditions. In general, the transmission error predictions compare favorably with the measured noise levels.

  2. Predictions of Supersonic Jet Mixing and Shock-Associated Noise Compared With Measured Far-Field Data

    NASA Technical Reports Server (NTRS)

    Dahl, Milo D.

    2010-01-01

    Codes for predicting supersonic jet mixing and broadband shock-associated noise were assessed using a database containing noise measurements of a jet issuing from a convergent nozzle. Two types of codes were used to make predictions. Fast running codes containing empirical models were used to compute both the mixing noise component and the shock-associated noise component of the jet noise spectrum. One Reynolds-averaged, Navier-Stokes-based code was used to compute only the shock-associated noise. To enable the comparisons of the predicted component spectra with data, the measured total jet noise spectra were separated into mixing noise and shock-associated noise components. Comparisons were made for 1/3-octave spectra and some power spectral densities using data from jets operating at 24 conditions covering essentially 6 fully expanded Mach numbers with 4 total temperature ratios.

  3. Prediction of the interior noise levels of high-speed propeller-driven aircraft

    NASA Technical Reports Server (NTRS)

    Rennison, D. C.; Wilby, J. F.; Wilby, E. G.

    1980-01-01

    The theoretical basis for an analytical model developed to predict the interior noise levels of high-speed propeller-driven airplanes is presented. Particular emphasis is given to modeling the transmission of discrete tones through a fuselage element into a cavity, estimates for the mean and standard deviation of the acoustic power flow, the coupling between a non-homogeneous excitation and the fuselage vibration response, and the prediction of maximum interior noise levels. The model allows for convenient examination of the various roles of the excitation and fuselage structural characteristics on the fuselage vibration response and the interior noise levels, as is required for the design of model or prototype noise control validation tests.

  4. Data analysis and noise prediction for the QF-1B experimental fan stage

    NASA Technical Reports Server (NTRS)

    Bliss, D. B.; Chandiramani, K. L.; Piersol, A. G.

    1976-01-01

    The results of a fan noise data analysis and prediction effort using experimental data obtained from tests on the QF-1B research fan are described. Surface pressure measurements were made with flush mounted sensors installed on selected rotor blades and stator vanes and noise measurements were made by microphones located at the far field. Power spectral density analysis, time history studies, and calculation of coherence functions were made. The emphasis of these studies was on the characteristics of tones in the spectra. The amplitude behavior of spectral tones was found to have a large, often predominant, random component, suggesting that turbulent processes play an important role in the generation of tonal as well as broadband noise. Inputs from the data analysis were used in a prediction method which assumes that acoustic dipoles, produced by unsteady blade and van forces, are the important source of fan noise.

  5. TFaNS Tone Fan Noise Design/Prediction System. Volume 3; Evaluation of System Codes

    NASA Technical Reports Server (NTRS)

    Topol, David A.

    1999-01-01

    TFANS is the Tone Fan Noise Design/Prediction System developed by Pratt & Whitney under contract to NASA Lewis (presently NASA Glenn). The purpose of this system is to predict tone noise emanating from a fan stage including the effects of reflection and transmission by the rotor and stator and by the duct inlet and nozzle. These effects have been added to an existing annular duct/isolated stator noise prediction capability. TFANS consists of: The codes that compute the acoustic properties (reflection and transmission coefficients) of the various elements and write them to files. Cup3D: Fan Noise Coupling Code that reads these files, solves the coupling problem, and outputs the desired noise predictions. AWAKEN: CFD/Measured Wake Postprocessor which reformats CFD wake predictions and/or measured wake data so it can be used by the system. This volume of the report evaluates TFANS versus full-scale and ADP 22" fig data using the semi-empirical wake modelling in the system. This report is divided into three volumes: Volume 1: System Description, CUP3D Technical Documentation, and Manual for Code Developers; Volume II: User's Manual, TFANS Version 1.4; Volume III: Evaluation of System Codes.

  6. Experimental validation of finite element and boundary element methods for predicting structural vibration and radiated noise

    NASA Technical Reports Server (NTRS)

    Seybert, A. F.; Wu, T. W.; Wu, X. F.

    1994-01-01

    This research report is presented in three parts. In the first part, acoustical analyses were performed on modes of vibration of the housing of a transmission of a gear test rig developed by NASA. The modes of vibration of the transmission housing were measured using experimental modal analysis. The boundary element method (BEM) was used to calculate the sound pressure and sound intensity on the surface of the housing and the radiation efficiency of each mode. The radiation efficiency of each of the transmission housing modes was then compared to theoretical results for a finite baffled plate. In the second part, analytical and experimental validation of methods to predict structural vibration and radiated noise are presented. A rectangular box excited by a mechanical shaker was used as a vibrating structure. Combined finite element method (FEM) and boundary element method (BEM) models of the apparatus were used to predict the noise level radiated from the box. The FEM was used to predict the vibration, while the BEM was used to predict the sound intensity and total radiated sound power using surface vibration as the input data. Vibration predicted by the FEM model was validated by experimental modal analysis; noise predicted by the BEM was validated by measurements of sound intensity. Three types of results are presented for the total radiated sound power: sound power predicted by the BEM model using vibration data measured on the surface of the box; sound power predicted by the FEM/BEM model; and sound power measured by an acoustic intensity scan. In the third part, the structure used in part two was modified. A rib was attached to the top plate of the structure. The FEM and BEM were then used to predict structural vibration and radiated noise respectively. The predicted vibration and radiated noise were then validated through experimentation.

  7. 14 CFR Appendix C to Part 147 - Airframe Curriculum Subjects

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 3 2014-01-01 2014-01-01 false Airframe Curriculum Subjects C Appendix C... (CONTINUED) SCHOOLS AND OTHER CERTIFICATED AGENCIES AVIATION MAINTENANCE TECHNICIAN SCHOOLS Pt. 147, App. C Appendix C to Part 147—Airframe Curriculum Subjects This appendix lists the subjects required in at...

  8. 14 CFR 65.85 - Airframe rating; additional privileges.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 2 2011-01-01 2011-01-01 false Airframe rating; additional privileges. 65.85 Section 65.85 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) AIRMEN CERTIFICATION: AIRMEN OTHER THAN FLIGHT CREWMEMBERS Mechanics § 65.85 Airframe...

  9. Development of hybrid method for the prediction of underwater propeller noise

    NASA Astrophysics Data System (ADS)

    Seol, Hanshin; Suh, Jung-Chun; Lee, Soogab

    2005-11-01

    Noise reduction and control is an important problem in the performance of underwater acoustic systems and in the habitability of the passenger ship for crew and passenger. Furthermore, sound generated by a propeller is critical in underwater detection and it is often related to the survivability of the vessel especially for military purpose. This paper presents a numerical study on the non-cavitating and blade sheet cavitation noises of the underwater propeller. A brief summary of numerical method with verification and results are presented. The noise is predicted using time-domain acoustic analogy. The flow field is analyzed with potential-based panel method, and then the time-dependent pressure and sheet cavity volume data are used as the input for Ffowcs Williams-Hawkings formulation to predict the far-field acoustics. Noise characteristics are presented according to noise sources and conditions. Through this study, the dominant noise source of the underwater propeller is analyzed, which will provide a basis for proper noise control strategies.

  10. Study on Prediction of Underwater Radiated Noise from Propeller Tip Vortex Cavitation

    NASA Astrophysics Data System (ADS)

    Yamada, Takuyoshi; Sato, Kei; Kawakita, Chiharu; Oshima, Akira

    2015-12-01

    The method to predict underwater radiated noise from tip vortex cavitation was studied. The growth of a single cavitation bubble in tip vortex was estimated by substituting the tip vortex to Rankine combined vortex. The ideal spectrum function for the sound pressure generated by a single cavitation bubble was used, also the empirical factor for the number of collapsed bubbles per unit time was introduced. The estimated noise data were compared with measured ship's ones and it was found out that this method can estimate noise data within 3dB difference.

  11. Multisensor multipulse Linear Predictive Coding (LPC) analysis in noise for medium rate speech transmission

    NASA Astrophysics Data System (ADS)

    Preuss, R. D.

    1985-12-01

    The theory of multipulse linear predictive coding (LPC) analysis is extended to include the possible presence of acoustic noise, as for a telephone near a busy road. Models are developed assuming two signals are provided: the primary signal is the output of a microphone which samples the combined acoustic fields of the noise and the speech, while the secondary signal is the output of a microphone which samples the acoustic field of the noise alone. Analysis techniques to extract the multipulse LPC parameters from these two signals are developed; these techniques are developed as approximations to maximum likelihood analysis for the given model.

  12. Development of a Jet Noise Prediction Method for Installed Jet Configurations

    NASA Technical Reports Server (NTRS)

    Hunter, Craig A.; Thomas, Russell H.

    2003-01-01

    This paper describes development of the Jet3D noise prediction method and its application to heated jets with complex three-dimensional flow fields and installation effects. Noise predictions were made for four separate flow bypass ratio five nozzle configurations tested in the NASA Langley Jet Noise Laboratory. These configurations consist of a round core and fan nozzle with and without pylon, and an eight chevron core nozzle and round fan nozzle with and without pylon. Predicted SPL data were in good agreement with experimental noise measurements up to 121 inlet angle, beyond which Jet3D under predicted low frequency levels. This is due to inherent limitations in the formulation of Lighthill's Acoustic Analogy used in Jet3D, and will be corrected in ongoing development. Jet3D did an excellent job predicting full scale EPNL for nonchevron configurations, and captured the effect of the pylon, correctly predicting a reduction in EPNL. EPNL predictions for chevron configurations were not in good agreement with measured data, likely due to the lower mixing and longer potential cores in the CFD simulations of these cases.

  13. Prediction of airplane cabin noise due to engine shock cell excitation using statistical energy analysis

    NASA Astrophysics Data System (ADS)

    Marshall, Steven E.

    As part of the effort in the 1980's to design fuel efficient propulsion systems (unducted fan engines) for large commercial airplanes, procedures were developed for predicting interior noise using statistical energy analysis (SEA). Due to stable fuel process and deregulation in the airline industry, the emphasis for propulsion systems on commercial airplanes shifted to higher thrust and lower operating costs. In order to preserve and enhance the knowledge acquired using SEA to predict cabin noise for propeller airplanes, potential noise control applications for more conventional airplane configurations were investigated. The present paper records an effort to extend the experience acquired using statistical energy analysis for unducted fan engines to noise generated by turbofan engine exhaust. The technique is applied to the generic case of a large commercial airplane with twin, wing-mounted engines. Results are presented from an evaluation of the noise source based on an uncommon set of flight test data. Model construction is decribed and prediction results compared to the flight test data. It is then demonstrated how SEA is used to prioritize the transmission paths and judge the merit of the common noise suppression techniques.

  14. 2nd Generation RLV Airframe Structures and Materials

    NASA Technical Reports Server (NTRS)

    Johnson, Theodore F.

    2000-01-01

    The goals and objectives of the project summarized in this viewgraph presentation are the following: (1) Develop and demonstrate verified airframe and cryotank structural design and analysis technologies, including damage tolerance, safety, reliability, and residual strength technologies, robust nonlinear shell and cryotank analysis technologies, high-fidelity analysis and design technologies for local structural detail features and joints, and high-fidelity analysis technologies for sandwich structures; (2) Demonstrate low cost, robust materials and processing, including polymeric matrix composite (PMC) and metallic materials and processing, and refractory composite and metallic hot structures materials and processing; (3) Develop and demonstrate robust airframe structures and validated integrated airframe structural concepts, including low cost fabrication and joining, operations efficient designs and inspection techniques (non-destructive evaluation), scale-up and integrated thermal structure tests, and airframe structures IVHM; (4) Demonstrate low cost, robust repair techniques; and (5) Develop verified integrated airframe structural concepts, including integrated structural concepts.

  15. Propulsion Airframe Aeroacoustic Integration Effects for a Hybrid Wing Body Aircraft Configuration

    NASA Technical Reports Server (NTRS)

    Czech, Michael J.; Thomas, Russell H; Elkoby, Ronen

    2012-01-01

    An extensive experimental investigation was performed to study the propulsion airframe aeroacoustic effects of a high bypass ratio engine for a hybrid wing body aircraft configuration where the engine is installed above the wing. The objective was to provide an understanding of the jet noise shielding effectiveness as a function of engine gas condition and location as well as nozzle configuration. A 4.7% scale nozzle of a bypass ratio seven engine was run at characteristic cycle points under static and forward flight conditions. The effect of the pylon and its orientation on jet noise was also studied as a function of bypass ratio and cycle condition. The addition of a pylon yielded significant spectral changes lowering jet noise by up to 4 dB at high polar angles and increasing it by 2 to 3 dB at forward angles. In order to assess jet noise shielding, a planform representation of the airframe model, also at 4.7% scale was traversed such that the jet nozzle was positioned from downstream of to several diameters upstream of the airframe model trailing edge. Installations at two fan diameters upstream of the wing trailing edge provided only limited shielding in the forward arc at high frequencies for both the axisymmetric and a conventional round nozzle with pylon. This was consistent with phased array measurements suggesting that the high frequency sources are predominantly located near the nozzle exit and, consequently, are amenable to shielding. The mid to low frequency sources were observed further downstream and shielding was insignificant. Chevrons were designed and used to impact the distribution of sources with the more aggressive design showing a significant upstream migration of the sources in the mid frequency range. Furthermore, the chevrons reduced the low frequency source levels and the typical high frequency increase due to the application of chevron nozzles was successfully shielded. The pylon was further modified with a technology that injects air

  16. Measurement and prediction of broadband noise from large horizontal axis wind turbine generators

    NASA Technical Reports Server (NTRS)

    Grosveld, F. W.; Shepherd, K. P.; Hubbard, H. H.

    1995-01-01

    A method is presented for predicting the broadband noise spectra of large wind turbine generators. It includes contributions from such noise sources as the inflow turbulence to the rotor, the interactions between the turbulent boundary layers on the blade surfaces with their trailing edges and the wake due to a blunt trailing edge. The method is partly empirical and is based on acoustic measurements of large wind turbines and airfoil models. Spectra are predicted for several large machines including the proposed MOD-5B. Measured data are presented for the MOD-2, the WTS-4, the MOD-OA, and the U.S. Windpower Inc. machines. Good agreement is shown between the predicted and measured far field noise spectra.

  17. Measurement and prediction of broadband noise from large horizontal axis wind turbine generators

    NASA Astrophysics Data System (ADS)

    Grosveld, F. W.; Shepherd, K. P.; Hubbard, H. H.

    1995-05-01

    A method is presented for predicting the broadband noise spectra of large wind turbine generators. It includes contributions from such noise sources as the inflow turbulence to the rotor, the interactions between the turbulent boundary layers on the blade surfaces with their trailing edges and the wake due to a blunt trailing edge. The method is partly empirical and is based on acoustic measurements of large wind turbines and airfoil models. Spectra are predicted for several large machines including the proposed MOD-5B. Measured data are presented for the MOD-2, the WTS-4, the MOD-OA, and the U.S. Windpower Inc. machines. Good agreement is shown between the predicted and measured far field noise spectra.

  18. Supersonic jet noise prediction and noise source investigation for realistic baseline and chevron nozzles based on hybrid RANS/LES simulations

    NASA Astrophysics Data System (ADS)

    Du, Yongle

    Jet noise simulations have been performed for a military-style baseline nozzle and a chevron nozzle with design Mach numbers of Md = 1:5 operating at several off-design conditions. The objective of the current numerical study is to provide insight into the noise generation mechanisms of shock-containing supersonic hot jets and the noise reduction mechanisms of chevron nozzles. A hybrid methodology combining advanced CFD technologies and the acoustic analogy is used for supersonic jet noise simulations. Unsteady Reynolds-averaged Navier-Stokes (URANS) equations are solved to predict the turbulent noise sources in the jet flows. A modified version of the Detached Eddy Simulation (DES) approach is used to avoid excessive damping of fine scale turbulent fluctuations. A multiblock structured mesh topology is used to represent complex nozzle geometries, including the faceted inner contours and finite nozzle thickness. A block interface condition is optimized for the complex multiblock mesh topology to avoid the centerline singularity. A fourth-order Dispersion-Relation-Preserving (DRP) scheme is used for spatial discretization. To enable efficient calculations, a dual time-stepping method is used in addition to parallel computation using MPI. Both multigrid and implicit residual smoothing are used to accelerate the convergence rate of sub-iterations in the fictitious time domain. Noise predictions are made with the permeable surface Ffowcs Williams and Hawkings (FWH) solution. All the numerical methods have been implemented in the jet flow simulation code "CHOPA" and the noise prediction code "PSJFWH". The computer codes have been validated with several benchmark cases. A preliminary study has been performed for an under-expanded baseline nozzle jet with Mj = 1:56 to validate the accuracy of the jet noise simulations. The results show that grid refinement around the jet potential core and the use of a lower artificial dissipation improve the resolution of the predicted

  19. Measurements and Predictions of the Noise from Three-Stream Jets

    NASA Technical Reports Server (NTRS)

    Henderson, Brenda S.; Leib, Stewart J.; Wernet, Mark P.

    2015-01-01

    An experimental and numerical investigation of the noise produced by high-subsonic and supersonic three-stream jets was conducted. The exhaust system consisted of externally-mixed-convergent nozzles and an external plug. Bypass- and tertiary- to-core area ratios between 1.0 and 2.5, and 0.4 and 1.0, respectively, were studied. Axisymmetric and offset tertiary nozzles were investigated for heated and unheated conditions. For axisymmetric configurations, the addition of the third stream was found to reduce peak- and high-frequency acoustic levels in the peak-jet-noise direction, with greater reductions at the lower bypass-to-core area ratios. For the offset configurations, an offset duct was found to decrease acoustic levels on the thick side of the tertiary nozzle relative to those produced by the simulated two-stream jet with up to 8 dB mid-frequency noise reduction at large angles to the jet inlet axis. Noise reduction in the peak-jet-noise direction was greater for supersonic core speeds than for subsonic core speeds. The addition of a tertiary nozzle insert used to divert the third-stream jet to one side of the nozzle system provided no noise reduction. Noise predictions are presented for selected cases using a method based on an acoustic analogy with mean flow interaction effects accounted for using a Green's function, computed in terms of its coupled azimuthal modes for the offset cases, and a source model previously used for round and rectangular jets. Comparisons of the prediction results with data show that the noise model predicts the observed increase in low-frequency noise with the introduction of a third, axisymmetric stream, but not the high-frequency reduction. For an offset third stream, the model predicts the observed trend of decreased sound levels on the thick side of the jet compared with the thin side, but the predicted azimuthal variations are much less than those seen in the data. Also, the shift of the spectral peak to lower frequencies with

  20. Measurements and Predictions of the Noise from Three-Stream Jets

    NASA Technical Reports Server (NTRS)

    Henderson, Brenda S.; Leib, Stewart J.; Wernet, Mark P.

    2015-01-01

    An experimental and numerical investigation of the noise produced by high-subsonic and supersonic three-stream jets was conducted. The exhaust system consisted of externally-mixed-convergent nozzles and an external plug. Bypass- and tertiary-to-core area ratios between 1.0 and 2.5, and 0.4 and 1.0, respectively, were studied. Axisymmetric and offset tertiary nozzles were investigated for heated and unheated conditions. For axisymmetric configurations, the addition of the third stream was found to reduce peak- and high-frequency acoustic levels in the peak-jet-noise direction, with greater reductions at the lower bypass-to-core area ratios. For the offset configurations, an offset duct was found to decrease acoustic levels on the thick side of the tertiary nozzle relative to those produced by the simulated two-stream jet with up to 8 dB mid-frequency noise reduction at large angles to the jet inlet axis. Noise reduction in the peak-jet-noise direction was greater for supersonic core speeds than for subsonic core speeds. The addition of a tertiary nozzle insert used to divert the third-stream jet to one side of the nozzle system provided no noise reduction. Noise predictions are presented for selected cases using a method based on an acoustic analogy with mean flow interaction effects accounted for using a Green's function, computed in terms of its coupled azimuthal modes for the offset cases, and a source model previously used for round and rectangular jets. Comparisons of the prediction results with data show that the noise model predicts the observed increase in low-frequency noise with the introduction of a third, axisymmetric stream, but not the high-frequency reduction. For an offset third stream, the model predicts the observed trend of decreased sound levels on the thick side of the jet compared with the thin side, but the predicted azimuthal variations are much less than those seen in the data. Also, the shift of the spectral peak to lower frequencies with

  1. JT150 1/2-scale nozzle jet noise experiment and comparison with prediction

    NASA Astrophysics Data System (ADS)

    Groesbeck, D. E.; Wasserbauer, C. A.

    1983-05-01

    As part of a program to study flight effects on the exhaust noise of a full scale JT15D engine, static half scale model jet noise experiments were conducted. Acoustic data were recorded for microphone angles of 45 deg to 155 deg with jet conditions for the model scale nozzle corresponding closely to those at 55, 73 and 97 percent of corrected rated speed for the full scale engine. These data are useful for determining the relative importance of jet and core noise in the static full scale engine test data and will in turn allow for a proper evaluation of flight effects on the exhaust noise results. The model scale data are also compared with the coaxial jet noise prediction. Above 1000 Hz, the prediction is nominally 0 to 3 dB higher than the data. The arithmetic mean of the differences between the experimental OASPL and the predicted OASPL for all angles for each run ranged from 0 to -3.2 dB. The standard deviation of all the OASPL differences is 2.2 dB. The discrepancies are greatest at low primary jet velocities and appear to be due to inadequacy in the variable jet density exponent incorporated in the prediction procedure.

  2. Advanced turboprop noise prediction: Development of a code at NASA Langley based on recent theoretical results

    NASA Technical Reports Server (NTRS)

    Farassat, F.; Dunn, M. H.; Padula, S. L.

    1986-01-01

    The development of a high speed propeller noise prediction code at Langley Research Center is described. The code utilizes two recent acoustic formulations in the time domain for subsonic and supersonic sources. The structure and capabilities of the code are discussed. Grid size study for accuracy and speed of execution on a computer is also presented. The code is tested against an earlier Langley code. Considerable increase in accuracy and speed of execution are observed. Some examples of noise prediction of a high speed propeller for which acoustic test data are available are given. A brisk derivation of formulations used is given in an appendix.

  3. ANOPP programmer's reference manual for the executive System. [aircraft noise prediction program

    NASA Technical Reports Server (NTRS)

    Gillian, R. E.; Brown, C. G.; Bartlett, R. W.; Baucom, P. H.

    1977-01-01

    Documentation for the Aircraft Noise Prediction Program as of release level 01/00/00 is presented in a manual designed for programmers having a need for understanding the internal design and logical concepts of the executive system software. Emphasis is placed on providing sufficient information to modify the system for enhancements or error correction. The ANOPP executive system includes software related to operating system interface, executive control, and data base management for the Aircraft Noise Prediction Program. It is written in Fortran IV for use on CDC Cyber series of computers.

  4. Flow structure generated by perpendicular blade vortex interaction and implications for helicopter noise predictions

    NASA Technical Reports Server (NTRS)

    Devenport, William J.; Glegg, Stewart A. L.

    1994-01-01

    Activities carried out in support of research on flow structure generated by perpendicular blade vortex interaction and implications for helicopter noise prediction are summarized. Progress in the following areas is described: (1) construction of 8 inch-chord NACA 0012 full-span blade; (2) Acquisition of two full-span blades; (3) preparation for hot wire measurements; (4) related work on a modified Betz's theory; and (5) work related to helicopter noise prediction. In addition, a list of publications based on the results of prior experimentation is presented.

  5. Noise produced by turbulent flow into a rotor: Users manual for atmospheric turbulence prediction and mean flow and turbulence contraction prediction

    NASA Technical Reports Server (NTRS)

    Simonich, J. C.; Caplin, B.

    1989-01-01

    A users manual for a computer program for predicting atmospheric turbulence and mean flow and turbulence contraction as part of a noise prediction scheme for nonisotropic turbulence ingestion noise in helicopters is described. Included are descriptions of the various program modules and subroutines, their function, programming structure, and the required input and output variables. This routine is incorporated as one module of NASA's ROTONET helicopter noise prediction program.

  6. International scale implementation of the CNOSSOS-EU road traffic noise prediction model for epidemiological studies.

    PubMed

    Morley, D W; de Hoogh, K; Fecht, D; Fabbri, F; Bell, M; Goodman, P S; Elliott, P; Hodgson, S; Hansell, A L; Gulliver, J

    2015-11-01

    The EU-FP7-funded BioSHaRE project is using individual-level data pooled from several national cohort studies in Europe to investigate the relationship of road traffic noise and health. The detailed input data (land cover and traffic characteristics) required for noise exposure modelling are not always available over whole countries while data that are comparable in spatial resolution between different countries is needed for harmonised exposure assessment. Here, we assess the feasibility using the CNOSSOS-EU road traffic noise prediction model with coarser input data in terms of model performance. Starting with a model using the highest resolution datasets, we progressively introduced lower resolution data over five further model runs and compared noise level estimates to measurements. We conclude that a low resolution noise model should provide adequate performance for exposure ranking (Spearman's rank = 0.75; p < 0.001), but with relatively large errors in predicted noise levels (RMSE = 4.46 dB(A)). PMID:26232738

  7. An Assessment of Open Rotor Noise Prediction Tools

    NASA Technical Reports Server (NTRS)

    Envia, Ed

    2012-01-01

    Assess the current capability for predicting the aerodynamic and acoustic performance of open rotors. The testbed is a GE blade set called F31/A31 for which significant amount of aerodynamic and acoustic data was acquired in model scale tests. F31/A31 is a vintage 1990s design with a 12-bladed front rotor and a 10-bladed aft rotor. This blade set was tested in both low-speed regime (representative of approach and takeoff conditions) and high-speed regime (representative of climb and cruise conditions). Uninstalled as well as installed configurations were tested. The focus of this interim presentation is on a subset of the low-speed tests for which the tip speed was varied, but the blade setting angles and tunnel Mach number were held fixed.

  8. Robotic dry stripping of airframes - Phase II

    NASA Astrophysics Data System (ADS)

    Pauli, Robert A.; Wittenberg, Art M.

    1989-03-01

    This paper describes a program for the development of a dust-free closed-cycle robotic system for dry stripping of airframes, designed to insure dust-free work environment and reduce plastic-media loss, the contamination risk, and the media inventory requirement. Phase I of the program involved building a prototype of the proposed robotic arm and its dust enclosure to prove basic automation concepts, showing reasonable paint removal rate from a curved surface, and establishing that the process is dust-free and recovers plastic media in a closed-cycle fashion. This paper contains calculations on the effect of different blasting parameters in order to determine optimum values required for the completion of Phase I. Also presented is the progress achieved by the Phase II of the program, which is to prove the total concept by building the complete system and demonstrating its capability.

  9. An advanced arc track resistant airframe wire

    NASA Astrophysics Data System (ADS)

    Beatty, J.

    1995-11-01

    Tensolite, a custom cable manufacturer specializing in high temperature materials as the dielectric medium, develops an advance arc track resistant airframe wire called Tufflite 2000. Tufflite 2000 has the following advantages over the other traditional wires: lighter weight and smaller in diameter; excellent wet and dry arc track resistance; superior dynamic cut-through performance even at elevated temperatures; flight proven performance on Boeing 737 and 757 airplanes; and true 260 C performance by utilizing Nickel plated copper conductors. This paper reports the different tests performed on Tufflite 2000: accelerated aging, arc resistance (wet and dry), dynamic cut through, humidity resistance, wire-to-wire abrasion, flammability, smoke, weight, notch sensitivity, flexibility, and markability. It particularly focuses on the BSI (British Standards Institute) dry arc resistance test and BSI wet arc tracking.

  10. An advanced arc track resistant airframe wire

    NASA Technical Reports Server (NTRS)

    Beatty, J.

    1995-01-01

    Tensolite, a custom cable manufacturer specializing in high temperature materials as the dielectric medium, develops an advance arc track resistant airframe wire called Tufflite 2000. Tufflite 2000 has the following advantages over the other traditional wires: lighter weight and smaller in diameter; excellent wet and dry arc track resistance; superior dynamic cut-through performance even at elevated temperatures; flight proven performance on Boeing 737 and 757 airplanes; and true 260 C performance by utilizing Nickel plated copper conductors. This paper reports the different tests performed on Tufflite 2000: accelerated aging, arc resistance (wet and dry), dynamic cut through, humidity resistance, wire-to-wire abrasion, flammability, smoke, weight, notch sensitivity, flexibility, and markability. It particularly focuses on the BSI (British Standards Institute) dry arc resistance test and BSI wet arc tracking.

  11. Crashworthy airframe design concepts: Fabrication and testing

    NASA Technical Reports Server (NTRS)

    Cronkhite, J. D.; Berry, V. L.

    1982-01-01

    Crashworthy floor concepts applicable to general aviation aircraft metal airframe structures were investigated. Initially several energy absorbing lower fuselage structure concepts were evaluated. Full scale floor sections representative of a twin engine, general aviation airplane lower fuselage structure were designed and fabricated. The floors featured an upper high strength platform with an energy absorbing, crushable structure underneath. Eighteen floors were fabricated that incorporated five different crushable subfloor concepts. The floors were then evaluated through static and dynamic testing. Computer programs NASTRAN and KRASH were used for the static and dynamic analysis of the floor section designs. Two twin engine airplane fuselages were modified to incorporate the most promising crashworthy floor sections for test evaluation.

  12. Open Rotor Noise Prediction Methods at NASA Langley- A Technology Review

    NASA Technical Reports Server (NTRS)

    Farassat, F.; Dunn, Mark H.; Tinetti, Ana F.; Nark, Douglas M.

    2009-01-01

    Open rotors are once again under consideration for propulsion of the future airliners because of their high efficiency. The noise generated by these propulsion systems must meet the stringent noise standards of today to reduce community impact. In this paper we review the open rotor noise prediction methods available at NASA Langley. We discuss three codes called ASSPIN (Advanced Subsonic-Supersonic Propeller Induced Noise), FW - Hpds (Ffowcs Williams-Hawkings with penetrable data surface) and the FSC (Fast Scattering Code). The first two codes are in the time domain and the third code is a frequency domain code. The capabilities of these codes and the input data requirements as well as the output data are presented. Plans for further improvements of these codes are discussed. In particular, a method based on equivalent sources is outlined to get rid of spurious signals in the FW - Hpds code.

  13. Effective Jet Properties for the Prediction of Turbulent Mixing Noise Reduction by Water Injection

    NASA Technical Reports Server (NTRS)

    Kandula, Max; Lonergan, Michael J.

    2007-01-01

    A one-dimensional control volume formulation is developed for the determination of jet mixing noise reduction due to water injection. The analysis starts from the conservation of mass, momentum and energy for the control volume, and introduces the concept of effective jet parameters (jet temperature, jet velocity and jet Mach number). It is shown that the water to jet mass flow rate ratio is an important parameter characterizing the jet noise reduction on account of gas-to-droplet momentum and heat transfer. Two independent dimensionless invariant groups are postulated, and provide the necessary relations for the droplet size and droplet Reynolds number. Results are presented illustrating the effect of mass flow rate ratio on the jet mixing noise reduction for a range of jet Mach number and jet Reynolds number. Predictions from the model show satisfactory comparison with available test data on supersonic jets. The results suggest that significant noise reductions can be achieved at increased flow rate ratios.

  14. On Acoustic Source Specification for Rotor-Stator Interaction Noise Prediction

    NASA Technical Reports Server (NTRS)

    Nark, Douglas M.; Envia, Edmane; Burley, Caesy L.

    2010-01-01

    This paper describes the use of measured source data to assess the effects of acoustic source specification on rotor-stator interaction noise predictions. Specifically, the acoustic propagation and radiation portions of a recently developed coupled computational approach are used to predict tonal rotor-stator interaction noise from a benchmark configuration. In addition to the use of full measured data, randomization of source mode relative phases is also considered for specification of the acoustic source within the computational approach. Comparisons with sideline noise measurements are performed to investigate the effects of various source descriptions on both inlet and exhaust predictions. The inclusion of additional modal source content is shown to have a much greater influence on the inlet results. Reasonable agreement between predicted and measured levels is achieved for the inlet, as well as the exhaust when shear layer effects are taken into account. For the number of trials considered, phase randomized predictions follow statistical distributions similar to those found in previous statistical source investigations. The shape of the predicted directivity pattern relative to measurements also improved with phase randomization, having predicted levels generally within one standard deviation of the measured levels.

  15. Computational methods in the prediction of advanced subsonic and supersonic propeller induced noise: ASSPIN users' manual

    NASA Technical Reports Server (NTRS)

    Dunn, M. H.; Tarkenton, G. M.

    1992-01-01

    This document describes the computational aspects of propeller noise prediction in the time domain and the use of high speed propeller noise prediction program ASSPIN (Advanced Subsonic and Supersonic Propeller Induced Noise). These formulations are valid in both the near and far fields. Two formulations are utilized by ASSPIN: (1) one is used for subsonic portions of the propeller blade; and (2) the second is used for transonic and supersonic regions on the blade. Switching between the two formulations is done automatically. ASSPIN incorporates advanced blade geometry and surface pressure modelling, adaptive observer time grid strategies, and contains enhanced numerical algorithms that result in reduced computational time. In addition, the ability to treat the nonaxial inflow case has been included.

  16. Acoustic Prediction Methodology and Test Validation for an Efficient Low-Noise Hybrid Wing Body Subsonic Transport

    NASA Technical Reports Server (NTRS)

    Kawai, Ronald T. (Compiler)

    2011-01-01

    This investigation was conducted to: (1) Develop a hybrid wing body subsonic transport configuration with noise prediction methods to meet the circa 2007 NASA Subsonic Fixed Wing (SFW) N+2 noise goal of -52 dB cum relative to FAR 36 Stage 3 (-42 dB cum re: Stage 4) while achieving a -25% fuel burned compared to current transports (re :B737/B767); (2) Develop improved noise prediction methods for ANOPP2 for use in predicting FAR 36 noise; (3) Design and fabricate a wind tunnel model for testing in the LaRC 14 x 22 ft low speed wind tunnel to validate noise predictions and determine low speed aero characteristics for an efficient low noise Hybrid Wing Body configuration. A medium wide body cargo freighter was selected to represent a logical need for an initial operational capability in the 2020 time frame. The Efficient Low Noise Hybrid Wing Body (ELNHWB) configuration N2A-EXTE was evolved meeting the circa 2007 NRA N+2 fuel burn and noise goals. The noise estimates were made using improvements in jet noise shielding and noise shielding prediction methods developed by UC Irvine and MIT. From this the Quiet Ultra Integrated Efficient Test Research Aircraft #1 (QUIET-R1) 5.8% wind tunnel model was designed and fabricated.

  17. Fatigue Modeling via Mammalian Auditory System for Prediction of Noise Induced Hearing Loss.

    PubMed

    Sun, Pengfei; Qin, Jun; Campbell, Kathleen

    2015-01-01

    Noise induced hearing loss (NIHL) remains as a severe health problem worldwide. Existing noise metrics and modeling for evaluation of NIHL are limited on prediction of gradually developing NIHL (GDHL) caused by high-level occupational noise. In this study, we proposed two auditory fatigue based models, including equal velocity level (EVL) and complex velocity level (CVL), which combine the high-cycle fatigue theory with the mammalian auditory model, to predict GDHL. The mammalian auditory model is introduced by combining the transfer function of the external-middle ear and the triple-path nonlinear (TRNL) filter to obtain velocities of basilar membrane (BM) in cochlea. The high-cycle fatigue theory is based on the assumption that GDHL can be considered as a process of long-cycle mechanical fatigue failure of organ of Corti. Furthermore, a series of chinchilla experimental data are used to validate the effectiveness of the proposed fatigue models. The regression analysis results show that both proposed fatigue models have high corrections with four hearing loss indices. It indicates that the proposed models can accurately predict hearing loss in chinchilla. Results suggest that the CVL model is more accurate compared to the EVL model on prediction of the auditory risk of exposure to hazardous occupational noise.

  18. Fatigue Modeling via Mammalian Auditory System for Prediction of Noise Induced Hearing Loss.

    PubMed

    Sun, Pengfei; Qin, Jun; Campbell, Kathleen

    2015-01-01

    Noise induced hearing loss (NIHL) remains as a severe health problem worldwide. Existing noise metrics and modeling for evaluation of NIHL are limited on prediction of gradually developing NIHL (GDHL) caused by high-level occupational noise. In this study, we proposed two auditory fatigue based models, including equal velocity level (EVL) and complex velocity level (CVL), which combine the high-cycle fatigue theory with the mammalian auditory model, to predict GDHL. The mammalian auditory model is introduced by combining the transfer function of the external-middle ear and the triple-path nonlinear (TRNL) filter to obtain velocities of basilar membrane (BM) in cochlea. The high-cycle fatigue theory is based on the assumption that GDHL can be considered as a process of long-cycle mechanical fatigue failure of organ of Corti. Furthermore, a series of chinchilla experimental data are used to validate the effectiveness of the proposed fatigue models. The regression analysis results show that both proposed fatigue models have high corrections with four hearing loss indices. It indicates that the proposed models can accurately predict hearing loss in chinchilla. Results suggest that the CVL model is more accurate compared to the EVL model on prediction of the auditory risk of exposure to hazardous occupational noise. PMID:26691685

  19. Aircraft interior noise prediction using a structural-acoustic analogy in NASTRAN modal synthesis

    NASA Technical Reports Server (NTRS)

    Grosveld, Ferdinand W.; Sullivan, Brenda M.; Marulo, Francesco

    1988-01-01

    The noise induced inside a cylindrical fuselage model by shaker excitation is investigated theoretically and experimentally. The NASTRAN modal-synthesis program is used in the theoretical analysis, and the predictions are compared with experimental measurements in extensive graphs. Good general agreement is obtained, but the need for further refinements to account for acoustic-cavity damping and structural-acoustic interaction is indicated.

  20. Rotorcraft noise

    NASA Technical Reports Server (NTRS)

    Huston, R. J. (Compiler)

    1982-01-01

    The establishment of a realistic plan for NASA and the U.S. helicopter industry to develop a design-for-noise methodology, including plans for the identification and development of promising noise reduction technology was discussed. Topics included: noise reduction techniques, scaling laws, empirical noise prediction, psychoacoustics, and methods of developing and validing noise prediction methods.

  1. The Prediction of Jet Noise Ground Effects Using an Acoustic Analogy and a Tailored Green's Function

    NASA Technical Reports Server (NTRS)

    Miller, Steven A. E.

    2013-01-01

    An assessment of an acoustic analogy for the mixing noise component of jet noise in the presence of an infinite surface is presented. The reflection of jet noise by the ground changes the distribution of acoustic energy and is characterized by constructive and destructive interference patterns. The equivalent sources are modeled based on the two-point cross- correlation of the turbulent velocity fluctuations and a steady Reynolds-Averaged Navier-Stokes (RANS) solution. Propagation effects, due to reflection by the surface and refaction by the jet shear layer, are taken into account by calculating the vector Green's function of the linearized Euler equations (LEE). The vector Green's function of the LEE is written in relation to Lilley's equation; that is, approximated with matched asymptotic solutions and the Green's function of the convective Helmholtz equation. The Green's function of the convective Helmholtz equation for an infinite flat plane with impedance is the Weyl-van der Pol equation. Predictions are compared with an unheated Mach 0.95 jet produced by a nozzle with an exit diameter of 0.3302 meters. Microphones are placed at various heights and distances from the nozzle exit in the peak jet noise direction above an acoustically hard and an asphalt surface. The predictions are shown to accurately capture jet noise ground effects that are characterized by constructive and destructive interference patterns in the mid- and far-field and capture overall trends in the near-field.

  2. Predicting range performance of sampled imagers by treating aliased signal as target-dependent noise.

    PubMed

    Vollmerhausen, Richard H; Driggers, Ronald G; Wilson, David L

    2008-08-01

    This paper presents a new theory to predict the impact of sampling on target acquisition. The aliased signal that results from sampling is treated as noise. The aliased signal is different from detector noise in two ways. First, aliasing disappears as the target contrast decreases. Second, the image corruption due to aliasing gets worse with increased range. This is because sampling is constant in angle space, and targets become poorly sampled as range increases. The theory is presented, along with the results of three experiments. The match between model and experiment is excellent.

  3. Open Rotor Noise Prediction at NASA Langley - Capabilities, Research and Development

    NASA Technical Reports Server (NTRS)

    Farassat, Fereidoun

    2010-01-01

    The high fuel prices of recent years have caused the operating cost of the airlines to soar. In an effort to bring down the fuel consumption, the major aircraft engine manufacturers are now taking a fresh look at open rotors for the propulsion of future airliners. Open rotors, also known as propfans or unducted fans, can offer up to 30 per cent improvement in efficiency compared to high bypass engines of 1980 vintage currently in use in most civilian aircraft. NASA Langley researchers have contributed significantly to the development of aeroacoustic technology of open rotors. This report discusses the current noise prediction technology at Langley and reviews the input data requirements, strengths and limitations of each method as well as the associated problems in need of attention by the researchers. We present a brief history of research on the aeroacoustics of rotating blade machinery at Langley Research Center. We then discuss the available noise prediction codes for open rotors developed at NASA Langley and their capabilities. In particular, we present the two useful formulations used for the computation of noise from subsonic and supersonic surfaces. Here we discuss the open rotor noise prediction codes ASSPIN and one based on Ffowcs Williams-Hawkings equation with penetrable data surface (FW - Hpds). The scattering of sound from surfaces near the rotor are calculated using the fast scattering code (FSC) which is also discussed in this report. Plans for further improvements of these codes are given.

  4. Analysis of Acoustic Modeling and Sound Propagation in Aircraft Noise Prediction

    NASA Technical Reports Server (NTRS)

    Plotkin, Kenneth J.; Shepherd, Kevin P. (Technical Monitor)

    2006-01-01

    An analysis has been performed of measured and predicted aircraft noise levels around Denver International Airport. A detailed examination was made of 90 straight-out departures that yielded good measurements on multiple monitors. Predictions were made with INM 5, INM 6 and the simulation model NMSIM. Predictions were consistently lower than measurements, less so for the simulation model than for the integrated models. Lateral directivity ("installation effect") patterns were seen which are consistent with other recent measurements. Atmospheric absorption was determined to be a significant factor in the underprediction. Calculations of atmospheric attenuation were made over a full year of upper air data at seven locations across the United States. It was found that temperature/humidity effects could cause variations of up to +/-4 dB, depending on season, for the sites examined. It was concluded that local temperature and humidity should be accounted for in aircraft noise modeling.

  5. Mean Flow and Noise Prediction for a Separate Flow Jet With Chevron Mixers

    NASA Technical Reports Server (NTRS)

    Koch, L. Danielle; Bridges, James; Khavaran, Abbas

    2004-01-01

    Experimental and numerical results are presented here for a separate flow nozzle employing chevrons arranged in an alternating pattern on the core nozzle. Comparisons of these results demonstrate that the combination of the WIND/MGBK suite of codes can predict the noise reduction trends measured between separate flow jets with and without chevrons on the core nozzle. Mean flow predictions were validated against Particle Image Velocimetry (PIV), pressure, and temperature data, and noise predictions were validated against acoustic measurements recorded in the NASA Glenn Aeroacoustic Propulsion Lab. Comparisons are also made to results from the CRAFT code. The work presented here is part of an on-going assessment of the WIND/MGBK suite for use in designing the next generation of quiet nozzles for turbofan engines.

  6. A Noise-Filtering Method for Link Prediction in Complex Networks

    PubMed Central

    Ouyang, Bo

    2016-01-01

    Link prediction plays an important role in both finding missing links in networked systems and complementing our understanding of the evolution of networks. Much attention from the network science community are paid to figure out how to efficiently predict the missing/future links based on the observed topology. Real-world information always contain noise, which is also the case in an observed network. This problem is rarely considered in existing methods. In this paper, we treat the existence of observed links as known information. By filtering out noises in this information, the underlying regularity of the connection information is retrieved and then used to predict missing or future links. Experiments on various empirical networks show that our method performs noticeably better than baseline algorithms. PMID:26788737

  7. Landing gear noise attenuation

    NASA Technical Reports Server (NTRS)

    Moe, Jeffrey W. (Inventor); Whitmire, Julia (Inventor); Kwan, Hwa-Wan (Inventor); Abeysinghe, Amal (Inventor)

    2011-01-01

    A landing gear noise attenuator mitigates noise generated by airframe deployable landing gear. The noise attenuator can have a first position when the landing gear is in its deployed or down position, and a second position when the landing gear is in its up or stowed position. The noise attenuator may be an inflatable fairing that does not compromise limited space constraints associated with landing gear retraction and stowage. A truck fairing mounted under a truck beam can have a compliant edge to allow for non-destructive impingement of a deflected fire during certain conditions.

  8. Helicopter rotor rotational noise predictions based on measured high-frequency blade loads

    NASA Technical Reports Server (NTRS)

    Hosier, R. N.; Ramakrishnan, R.

    1974-01-01

    In tests conducted at the Langley helicopter rotor test facility, simultaneous measurements of up to 200 harmonics of the fluctuating aerodynamic blade surface pressures and far-field radiated noise were made on a full-scale nontranslating rotor system. After their characteristics were determined, the measured blade surface pressures were converted to loading coefficients and used in an existing theory to predict the far-field rotational noise. A comparison of the calculated and measured noise shows generally good agreement up to 300 to 600 Hz, depending on the discreteness of the loading spectrum. Specific attention is given to the effects of the blade loading coefficients, chordwise loading distributions, blade loading phases, and observer azimuthal position on the calculations.

  9. Predictive factors of occupational noise-induced hearing loss in Spanish workers: A prospective study

    PubMed Central

    Pelegrin, Armando Carballo; Canuet, Leonides; Rodríguez, Ángeles Arias; Morales, Maria Pilar Arévalo

    2015-01-01

    The purpose of our study was to identify the main factors associated with objective noise-induced hearing loss (NIHL), as indicated by abnormal audiometric testing, in Spanish workers exposed to occupational noise in the construction industry. We carried out a prospective study in Tenerife, Spain, using 150 employees exposed to occupational noise and 150 age-matched controls who were not working in noisy environments. The variables analyzed included sociodemographic data, noise-related factors, types of hearing protection, self-report hearing loss, and auditory-related symptoms (e.g., tinnitus, vertigo). Workers with pathological audiograms had significantly longer noise-exposure duration (16.2 ± 11.4 years) relative to those with normal audiograms (10.2 ± 7.0 years; t = 3.99, P < 0.001). The vast majority of those who never used hearing protection measures had audiometric abnormalities (94.1%). Additionally, workers using at least one of the protection devices (earplugs or earmuffs) had significantly more audiometric abnormalities than those using both protection measures simultaneously (Chi square = 16.07; P < 0.001). The logistic regression analysis indicates that the use of hearing protection measures [odds ratio (OR) = 12.30, confidence interval (CI) = 4.36-13.81, P < 0.001], and noise-exposure duration (OR = 1.35, CI = 1.08-1.99, P = 0.040) are significant predictors of NIHL. This regression model correctly predicted 78.2% of individuals with pathological audiograms. The combined use of hearing protection measures, in particular earplugs and earmuffs, associates with a lower rate of audiometric abnormalities in subjects with high occupational noise exposure. The use of hearing protection measures at work and noise-exposure duration are best predictive factors of NIHL. Auditory-related symptoms and self-report hearing loss do not represent good indicators of objective NIHL. Routine monitoring of noise levels and hearing status are of great importance as part

  10. Predictive factors of occupational noise-induced hearing loss in Spanish workers: A prospective study.

    PubMed

    Pelegrin, Armando Carballo; Canuet, Leonides; Rodríguez, Ángeles Arias; Morales, Maria Pilar Arévalo

    2015-01-01

    The purpose of our study was to identify the main factors associated with objective noise-induced hearing loss (NIHL), as indicated by abnormal audiometric testing, in Spanish workers exposed to occupational noise in the construction industry. We carried out a prospective study in Tenerife, Spain, using 150 employees exposed to occupational noise and 150 age-matched controls who were not working in noisy environments. The variables analyzed included sociodemographic data, noise-related factors, types of hearing protection, self-report hearing loss, and auditory-related symptoms (e.g., tinnitus, vertigo). Workers with pathological audiograms had significantly longer noise-exposure duration (16.2 ± 11.4 years) relative to those with normal audiograms (10.2 ± 7.0 years; t = 3.99, P < 0.001). The vast majority of those who never used hearing protection measures had audiometric abnormalities (94.1%). Additionally, workers using at least one of the protection devices (earplugs or earmuffs) had significantly more audiometric abnormalities than those using both protection measures simultaneously (Chi square = 16.07; P < 0.001). The logistic regression analysis indicates that the use of hearing protection measures [odds ratio (OR) = 12.30, confidence interval (CI) = 4.36-13.81, P < 0.001], and noise-exposure duration (OR = 1.35, CI = 1.08-1.99, P = 0.040) are significant predictors of NIHL. This regression model correctly predicted 78.2% of individuals with pathological audiograms. The combined use of hearing protection measures, in particular earplugs and earmuffs, associates with a lower rate of audiometric abnormalities in subjects with high occupational noise exposure. The use of hearing protection measures at work and noise-exposure duration are best predictive factors of NIHL. Auditory-related symptoms and self-report hearing loss do not represent good indicators of objective NIHL. Routine monitoring of noise levels and hearing status are of great importance as part

  11. Predictive factors of occupational noise-induced hearing loss in Spanish workers: A prospective study.

    PubMed

    Pelegrin, Armando Carballo; Canuet, Leonides; Rodríguez, Ángeles Arias; Morales, Maria Pilar Arévalo

    2015-01-01

    The purpose of our study was to identify the main factors associated with objective noise-induced hearing loss (NIHL), as indicated by abnormal audiometric testing, in Spanish workers exposed to occupational noise in the construction industry. We carried out a prospective study in Tenerife, Spain, using 150 employees exposed to occupational noise and 150 age-matched controls who were not working in noisy environments. The variables analyzed included sociodemographic data, noise-related factors, types of hearing protection, self-report hearing loss, and auditory-related symptoms (e.g., tinnitus, vertigo). Workers with pathological audiograms had significantly longer noise-exposure duration (16.2 ± 11.4 years) relative to those with normal audiograms (10.2 ± 7.0 years; t = 3.99, P < 0.001). The vast majority of those who never used hearing protection measures had audiometric abnormalities (94.1%). Additionally, workers using at least one of the protection devices (earplugs or earmuffs) had significantly more audiometric abnormalities than those using both protection measures simultaneously (Chi square = 16.07; P < 0.001). The logistic regression analysis indicates that the use of hearing protection measures [odds ratio (OR) = 12.30, confidence interval (CI) = 4.36-13.81, P < 0.001], and noise-exposure duration (OR = 1.35, CI = 1.08-1.99, P = 0.040) are significant predictors of NIHL. This regression model correctly predicted 78.2% of individuals with pathological audiograms. The combined use of hearing protection measures, in particular earplugs and earmuffs, associates with a lower rate of audiometric abnormalities in subjects with high occupational noise exposure. The use of hearing protection measures at work and noise-exposure duration are best predictive factors of NIHL. Auditory-related symptoms and self-report hearing loss do not represent good indicators of objective NIHL. Routine monitoring of noise levels and hearing status are of great importance as part

  12. Airframe Icing Research Gaps: NASA Perspective

    NASA Technical Reports Server (NTRS)

    Potapczuk, Mark

    2009-01-01

    qCurrent Airframe Icing Technology Gaps: Development of a full 3D ice accretion simulation model. Development of an improved simulation model for SLD conditions. CFD modeling of stall behavior for ice-contaminated wings/tails. Computational methods for simulation of stability and control parameters. Analysis of thermal ice protection system performance. Quantification of 3D ice shape geometric characteristics Development of accurate ground-based simulation of SLD conditions. Development of scaling methods for SLD conditions. Development of advanced diagnostic techniques for assessment of tunnel cloud conditions. Identification of critical ice shapes for aerodynamic performance degradation. Aerodynamic scaling issues associated with testing scale model ice shape geometries. Development of altitude scaling methods for thermal ice protections systems. Development of accurate parameter identification methods. Measurement of stability and control parameters for an ice-contaminated swept wing aircraft. Creation of control law modifications to prevent loss of control during icing encounters. 3D ice shape geometries. Collection efficiency data for ice shape geometries. SLD ice shape data, in-flight and ground-based, for simulation verification. Aerodynamic performance data for 3D geometries and various icing conditions. Stability and control parameter data for iced aircraft configurations. Thermal ice protection system data for simulation validation.

  13. Large Civil Tiltrotor (LCTR2) Interior Noise Predictions due to Turbulent Boundary Layer Excitation

    NASA Technical Reports Server (NTRS)

    Grosveld, Ferdinand W.

    2013-01-01

    The Large Civil Tiltrotor (LCTR2) is a conceptual vehicle that has a design goal to transport 90 passengers over a distance of 1800 km at a speed of 556 km/hr. In this study noise predictions were made in the notional LCTR2 cabin due to Cockburn/Robertson and Efimtsov turbulent boundary layer (TBL) excitation models. A narrowband hybrid Finite Element (FE) analysis was performed for the low frequencies (6-141 Hz) and a Statistical Energy Analysis (SEA) was conducted for the high frequency one-third octave bands (125- 8000 Hz). It is shown that the interior sound pressure level distribution in the low frequencies is governed by interactions between individual structural and acoustic modes. The spatially averaged predicted interior sound pressure levels for the low frequency hybrid FE and the high frequency SEA analyses, due to the Efimtsov turbulent boundary layer excitation, were within 1 dB in the common 125 Hz one-third octave band. The averaged interior noise levels for the LCTR2 cabin were predicted lower than the levels in a comparable Bombardier Q400 aircraft cabin during cruise flight due to the higher cruise altitude and lower Mach number of the LCTR2. LCTR2 cabin noise due to TBL excitation during cruise flight was found not unacceptable for crew or passengers when predictions were compared to an acoustic survey on a Q400 aircraft.

  14. The 136 MHz/400 MHz earth station antenna-noise temperature prediction program documentation for RAE-B

    NASA Technical Reports Server (NTRS)

    Chin, M.

    1972-01-01

    A simulation study to determine the 136 MHz and 400 MHz noise temperature of the ground network antennas which will track the RAE-B satellite during data transmission periods is described. Since the noise temperature of the antenna effectively sets the signal-to-noise ratio (SNR) of the received signal, a knowledge of SNR will be helpful in locating the optimum time windows for data transmission during low-noise periods. Antenna-noise temperatures at 136 MHz and 400 MHz will be predicted for selected earth-based ground stations which will support RAE-B. The antenna-noise temperature predictions will include the effects of galactic-brightness temperature, the sun, and the brightest radio stars. Predictions will cover the ten-month period from March 1, 1973 to December 31, 1973. The RAE-B mission will be expecially susceptible to SNR degradation during the two eclipses of the Sun occurring in this period.

  15. A survey of models for the prediction of ambient ocean noise: Circa 1995

    SciTech Connect

    Doolittle, R.

    1996-01-01

    The state of the art of model development for application to computer studies of undersea search systems utilizing acoustics is surveyed in this document. Due to the demands for surveillance of submarines operating in ocean basins, the development of noise models for application in deep oceans is fairly advanced and somewhat generic. This is due to the deep sound channel, discovered during World War II, which when present allows for long-range sound propagation with little or no interaction with the bottom. Exceptions to this channel, also well understood, are found in both the high latitudes where the sound is upward refracting and in tropical ocean areas with downward refracting sound transmission. The controlling parameter is the sound speed as a function of depth within the ocean, the sound speed profile. When independent of range, this profile may be converted to a noise-versus-depth profile with well-validated consequences for deep-ocean ambient noise. When considering ocean areas of shallow water, the littoral regions, the idea of a genenic ocean channel advisedly is abandoned. The locally unique nature of both the noise production mechanisms and of the channel carrying the sound, obviates the generic treatment. Nevertheless, idealizations of this case exist and promote the understanding if not the exact predictability of the statistics of shallow water ambient noise. Some examples of these models are given in this document.

  16. A method for predicting static-to-flight effects on coaxial jet noise

    NASA Astrophysics Data System (ADS)

    Bryce, William D.; Chinoy, Cyrus B.

    2016-08-01

    Previously-published work has provided a theoretical modelling of the jet noise from coaxial nozzle configurations in the form of component sources which can each be quantified in terms of modified single-stream jets. This modelling has been refined and extended to cover a wide range of the operating conditions of aircraft turbofan engines with separate exhaust flows, encompassing area ratios from 0.8 to 4. The objective has been to establish a basis for predicting the static-to-flight changes in the coaxial jet noise by applying single-stream flight effects to each of the sources comprising the modelling of the coaxial jet noise under static conditions. Relatively few experimental test points are available for validation although these do cover the full extent of the jet conditions and area ratios considered. The experimental results are limited in their frequency range by practical considerations but the static-to-flight changes in the third-octave SPLs are predicted to within a standard deviation of 0.4 dB although the complex effects of jet refraction and convection cause the errors to increase at low flight emission angles to the jet axis. The modelling also provides useful insights into the mechanisms involved in the generation of coaxial jet noise and has facilitated the identification of inadequacies in the experimental simulation of flight effects.

  17. An Analytical Assessment of NASA's N+1 Subsonic Fixed Wing Project Noise Goal

    NASA Technical Reports Server (NTRS)

    Berton, Jeffrey J.; Envia, Edmane; Burley, Casey L.

    2009-01-01

    The Subsonic Fixed Wing Project of NASA's Fundamental Aeronautics Program has adopted a noise reduction goal for new, subsonic, single-aisle, civil aircraft expected to replace current 737 and A320 airplanes. These so-called 'N+1' aircraft - designated in NASA vernacular as such since they will follow the current, in-service, 'N' airplanes - are hoped to achieve certification noise goal levels of 32 cumulative EPNdB under current Stage 4 noise regulations. A notional, N+1, single-aisle, twinjet transport with ultrahigh bypass ratio turbofan engines is analyzed in this study using NASA software and methods. Several advanced noise-reduction technologies are analytically applied to the propulsion system and airframe. Certification noise levels are predicted and compared with the NASA goal.

  18. An Analytical Assessment of NASA's N(+)1 Subsonic Fixed Wing Project Noise Goal

    NASA Technical Reports Server (NTRS)

    Berton, Jeffrey J.; Envia, Edmane; Burley, Casey L.

    2010-01-01

    The Subsonic Fixed Wing Project of NASA s Fundamental Aeronautics Program has adopted a noise reduction goal for new, subsonic, single-aisle, civil aircraft expected to replace current 737 and A320 airplanes. These so-called "N+1" aircraft--designated in NASA vernacular as such since they will follow the current, in-service, "N" airplanes--are hoped to achieve certification noise goal levels of 32 cumulative EPNdB under current Stage 4 noise regulations. A notional, N+1, single-aisle, twinjet transport with ultrahigh bypass ratio turbofan engines is analyzed in this study using NASA software and methods. Several advanced noise-reduction technologies are empirically applied to the propulsion system and airframe. Certification noise levels are predicted and compared with the NASA goal.

  19. A computer program to predict rotor rotational noise of a stationary rotor from blade loading coefficient

    NASA Technical Reports Server (NTRS)

    Ramakrishnan, R.; Randall, D.; Hosier, R. N.

    1976-01-01

    The programing language used is FORTRAN IV. A description of all main and subprograms is provided so that any user possessing a FORTRAN compiler and random access capability can adapt the program to his facility. Rotor blade surface-pressure spectra can be used by the program to calculate: (1) blade station loading spectra, (2) chordwise and/or spanwise integrated blade-loading spectra, and (3) far-field rotational noise spectra. Any of five standard inline functions describing the chordwise distribution of the blade loading can be chosen in order to study parametrically the acoustic predictions. The program output consists of both printed and graphic descriptions of the blade-loading coefficient spectra and far-field acoustic spectrum. The results may also be written on binary file for future processing. Examples of the application of the program along with a description of the rotational noise prediction theory on which the program is based are also provided.

  20. Users' manual for the Langley high speed propeller noise prediction program (DFP-ATP)

    NASA Technical Reports Server (NTRS)

    Dunn, M. H.; Tarkenton, G. M.

    1989-01-01

    The use of the Dunn-Farassat-Padula Advanced Technology Propeller (DFP-ATP) noise prediction program which computes the periodic acoustic pressure signature and spectrum generated by propellers moving with supersonic helical tip speeds is described. The program has the capacity of predicting noise produced by a single-rotation propeller (SRP) or a counter-rotation propeller (CRP) system with steady or unsteady blade loading. The computational method is based on two theoretical formulations developed by Farassat. One formulation is appropriate for subsonic sources, and the other for transonic or supersonic sources. Detailed descriptions of user input, program output, and two test cases are presented, as well as brief discussions of the theoretical formulations and computational algorithms employed.

  1. Signal-to-Noise Ratio Prediction and Validation for Space Shuttle GPS Flight Experiment

    NASA Technical Reports Server (NTRS)

    Hwu, Shian U.; Adkins, Antha A.; Loh, Yin-Chung; Brown, Lisa C.; Sham, Catherine C.; Kroll, Quin D.

    2002-01-01

    A deterministic method for Space Station Global Positioning System (GPS) Signal-To- Noise Ratio (SNR) predictions is proposed. The complex electromagnetic interactions between GPS antennas and surrounding Space Station structures are taken into account by computational electromagnetic technique. This computer simulator is capable of taking into account multipath effects from dynamically changed solar panels and thermal radiators. A comparison with recent collected Space Station GPS system flight experiment data is presented. The simulation results are in close agreement with flight data.

  2. The Application of a Boundary Integral Equation Method to the Prediction of Ducted Fan Engine Noise

    NASA Technical Reports Server (NTRS)

    Dunn, M. H.; Tweed, J.; Farassat, F.

    1999-01-01

    The prediction of ducted fan engine noise using a boundary integral equation method (BIEM) is considered. Governing equations for the BIEM are based on linearized acoustics and describe the scattering of incident sound by a thin, finite-length cylindrical duct in the presence of a uniform axial inflow. A classical boundary value problem (BVP) is derived that includes an axisymmetric, locally reacting liner on the duct interior. Using potential theory, the BVP is recast as a system of hypersingular boundary integral equations with subsidiary conditions. We describe the integral equation derivation and solution procedure in detail. The development of the computationally efficient ducted fan noise prediction program TBIEM3D, which implements the BIEM, and its utility in conducting parametric noise reduction studies are discussed. Unlike prediction methods based on spinning mode eigenfunction expansions, the BIEM does not require the decomposition of the interior acoustic field into its radial and axial components which, for the liner case, avoids the solution of a difficult complex eigenvalue problem. Numerical spectral studies are presented to illustrate the nexus between the eigenfunction expansion representation and BIEM results. We demonstrate BIEM liner capability by examining radiation patterns for several cases of practical interest.

  3. Interior Noise Predictions in the Preliminary Design of the Large Civil Tiltrotor (LCTR2)

    NASA Technical Reports Server (NTRS)

    Grosveld, Ferdinand W.; Cabell, Randolph H.; Boyd, David D.

    2013-01-01

    A prediction scheme was established to compute sound pressure levels in the interior of a simplified cabin model of the second generation Large Civil Tiltrotor (LCTR2) during cruise conditions, while being excited by turbulent boundary layer flow over the fuselage, or by tiltrotor blade loading and thickness noise. Finite element models of the cabin structure, interior acoustic space, and acoustically absorbent (poro-elastic) materials in the fuselage were generated and combined into a coupled structural-acoustic model. Fluctuating power spectral densities were computed according to the Efimtsov turbulent boundary layer excitation model. Noise associated with the tiltrotor blades was predicted in the time domain as fluctuating surface pressures and converted to power spectral densities at the fuselage skin finite element nodes. A hybrid finite element (FE) approach was used to compute the low frequency acoustic cabin response over the frequency range 6-141 Hz with a 1 Hz bandwidth, and the Statistical Energy Analysis (SEA) approach was used to predict the interior noise for the 125-8000 Hz one-third octave bands.

  4. An efficient and robust method for predicting helicopter rotor high-speed impulsive noise

    NASA Technical Reports Server (NTRS)

    Brentner, Kenneth S.

    1996-01-01

    A new formulation for the Ffowcs Williams-Hawkings quadrupole source, which is valid for a far-field in-plane observer, is presented. The far-field approximation is new and unique in that no further approximation of the quadrupole source strength is made and integrands with r(exp -2) and r(exp -3) dependence are retained. This paper focuses on the development of a retarded-time formulation in which time derivatives are analytically taken inside the integrals to avoid unnecessary computational work when the observer moves with the rotor. The new quadrupole formulation is similar to Farassat's thickness and loading formulation 1A. Quadrupole noise prediction is carried out in two parts: a preprocessing stage in which the previously computed flow field is integrated in the direction normal to the rotor disk, and a noise computation stage in which quadrupole surface integrals are evaluated for a particular observer position. Preliminary predictions for hover and forward flight agree well with experimental data. The method is robust and requires computer resources comparable to thickness and loading noise prediction.

  5. Measurement and prediction of noise from low-altitude military aircraft operations

    NASA Astrophysics Data System (ADS)

    Barry, Bernard F.; Payne, Richard C.; Harris, Anthony L.; Weston, Ralph J.

    1992-04-01

    In response to the rapid growth in demand for information on noise levels around military airfields in the UK, NPL developed AIRNOISE, a mathematical model for computing aircraft noise contours. Since its first applications in 1981, the model has been used to determine zones of eligibility within the MoD compensation scheme. The model has been subject to continuous development, e.g., the incorporation of Harrier V/STOL operations. We have now extended the model to include noise from high-speed, low-level operations. The model predicts not only maximum levels but the complete time-history, so that the time-onset rate can be estimated. To aid refinement and validation of the model, a special exercise has been conducted in which Tornado, Harrier, Jaguar, Hawk, F-15 and F-16 aircraft have flown straight and level at heights between about 100 and 400 feet, at various speeds and engine power settings over an array of microphones. This paper describes the trial and the results obtained. The prediction model is outlined and comparisons made between predictions and measurements.

  6. Prediction of Broadband Shock-Associated Noise Including Propagation Effects Originating NASA

    NASA Technical Reports Server (NTRS)

    Miller, Steven; Morris, Philip J.

    2012-01-01

    An acoustic analogy is developed based on the Euler equations for broadband shock-associated noise (BBSAN) that directly incorporates the vector Green s function of the linearized Euler equations and a steady Reynolds-Averaged Navier-Stokes solution (SRANS) to describe the mean flow. The vector Green s function allows the BBSAN propagation through the jet shear layer to be determined. The large-scale coherent turbulence is modeled by two-point second order velocity cross-correlations. Turbulent length and time scales are related to the turbulent kinetic energy and dissipation rate. An adjoint vector Green s function solver is implemented to determine the vector Green s function based on a locally parallel mean flow at different streamwise locations. The newly developed acoustic analogy can be simplified to one that uses the Green s function associated with the Helmholtz equation, which is consistent with a previous formulation by the authors. A large number of predictions are generated using three different nozzles over a wide range of fully-expanded jet Mach numbers and jet stagnation temperatures. These predictions are compared with experimental data from multiple jet noise experimental facilities. In addition, two models for the so-called fine-scale mixing noise are included in the comparisons. Improved BBSAN predictions are obtained relative to other models that do not include propagation effects.

  7. Open Rotor Tone Shielding Methods for System Noise Assessments Using Multiple Databases

    NASA Technical Reports Server (NTRS)

    Bahr, Christopher J.; Thomas, Russell H.; Lopes, Leonard V.; Burley, Casey L.; Van Zante, Dale E.

    2014-01-01

    Advanced aircraft designs such as the hybrid wing body, in conjunction with open rotor engines, may allow for significant improvements in the environmental impact of aviation. System noise assessments allow for the prediction of the aircraft noise of such designs while they are still in the conceptual phase. Due to significant requirements of computational methods, these predictions still rely on experimental data to account for the interaction of the open rotor tones with the hybrid wing body airframe. Recently, multiple aircraft system noise assessments have been conducted for hybrid wing body designs with open rotor engines. These assessments utilized measured benchmark data from a Propulsion Airframe Aeroacoustic interaction effects test. The measured data demonstrated airframe shielding of open rotor tonal and broadband noise with legacy F7/A7 open rotor blades. Two methods are proposed for improving the use of these data on general open rotor designs in a system noise assessment. The first, direct difference, is a simple octave band subtraction which does not account for tone distribution within the rotor acoustic signal. The second, tone matching, is a higher-fidelity process incorporating additional physical aspects of the problem, where isolated rotor tones are matched by their directivity to determine tone-by-tone shielding. A case study is conducted with the two methods to assess how well each reproduces the measured data and identify the merits of each. Both methods perform similarly for system level results and successfully approach the experimental data for the case study. The tone matching method provides additional tools for assessing the quality of the match to the data set. Additionally, a potential path to improve the tone matching method is provided.

  8. Development of Computational Aeroacoustics Code for Jet Noise and Flow Prediction

    NASA Technical Reports Server (NTRS)

    Keith, Theo G., Jr.; Hixon, Duane R.

    2002-01-01

    Accurate prediction of jet fan and exhaust plume flow and noise generation and propagation is very important in developing advanced aircraft engines that will pass current and future noise regulations. In jet fan flows as well as exhaust plumes, two major sources of noise are present: large-scale, coherent instabilities and small-scale turbulent eddies. In previous work for the NASA Glenn Research Center, three strategies have been explored in an effort to computationally predict the noise radiation from supersonic jet exhaust plumes. In order from the least expensive computationally to the most expensive computationally, these are: 1) Linearized Euler equations (LEE). 2) Very Large Eddy Simulations (VLES). 3) Large Eddy Simulations (LES). The first method solves the linearized Euler equations (LEE). These equations are obtained by linearizing about a given mean flow and the neglecting viscous effects. In this way, the noise from large-scale instabilities can be found for a given mean flow. The linearized Euler equations are computationally inexpensive, and have produced good noise results for supersonic jets where the large-scale instability noise dominates, as well as for the tone noise from a jet engine blade row. However, these linear equations do not predict the absolute magnitude of the noise; instead, only the relative magnitude is predicted. Also, the predicted disturbances do not modify the mean flow, removing a physical mechanism by which the amplitude of the disturbance may be controlled. Recent research for isolated airfoils' indicates that this may not affect the solution greatly at low frequencies. The second method addresses some of the concerns raised by the LEE method. In this approach, called Very Large Eddy Simulation (VLES), the unsteady Reynolds averaged Navier-Stokes equations are solved directly using a high-accuracy computational aeroacoustics numerical scheme. With the addition of a two-equation turbulence model and the use of a relatively

  9. Development of Computational Aeroacoustics Code for Jet Noise and Flow Prediction

    NASA Astrophysics Data System (ADS)

    Keith, Theo G., Jr.; Hixon, Duane R.

    2002-07-01

    Accurate prediction of jet fan and exhaust plume flow and noise generation and propagation is very important in developing advanced aircraft engines that will pass current and future noise regulations. In jet fan flows as well as exhaust plumes, two major sources of noise are present: large-scale, coherent instabilities and small-scale turbulent eddies. In previous work for the NASA Glenn Research Center, three strategies have been explored in an effort to computationally predict the noise radiation from supersonic jet exhaust plumes. In order from the least expensive computationally to the most expensive computationally, these are: 1) Linearized Euler equations (LEE). 2) Very Large Eddy Simulations (VLES). 3) Large Eddy Simulations (LES). The first method solves the linearized Euler equations (LEE). These equations are obtained by linearizing about a given mean flow and the neglecting viscous effects. In this way, the noise from large-scale instabilities can be found for a given mean flow. The linearized Euler equations are computationally inexpensive, and have produced good noise results for supersonic jets where the large-scale instability noise dominates, as well as for the tone noise from a jet engine blade row. However, these linear equations do not predict the absolute magnitude of the noise; instead, only the relative magnitude is predicted. Also, the predicted disturbances do not modify the mean flow, removing a physical mechanism by which the amplitude of the disturbance may be controlled. Recent research for isolated airfoils' indicates that this may not affect the solution greatly at low frequencies. The second method addresses some of the concerns raised by the LEE method. In this approach, called Very Large Eddy Simulation (VLES), the unsteady Reynolds averaged Navier-Stokes equations are solved directly using a high-accuracy computational aeroacoustics numerical scheme. With the addition of a two-equation turbulence model and the use of a relatively

  10. Applications of the predictability of the Coherent Noise Model to aftershock sequences

    NASA Astrophysics Data System (ADS)

    Christopoulos, Stavros-Richard; Sarlis, Nicholas

    2014-05-01

    A study [1] of the coherent noise model [2-4] in natural time [5-7] has shown that it exhibits predictability. Interestingly, one of the predictors suggested [1] for the coherent noise model can be generalized and applied to the case of (real) aftershock sequences. The results obtained [8] so far are beyond chance. Here, we apply this approach to several aftershock sequences of strong earthquakes with magnitudes Mw ≥6.9 in Indonesia, California and Greece, including the Mw9.2 earthquake that occurred on 26 December 2004 in Sumatra. References. [1] N. V. Sarlis and S.-R. G. Christopoulos, Predictability of the coherent-noise model and its applications, Physical Review E, 85, 051136, 2012. [2] M.E.J. Newman, Self-organized criticality, evolution and the fossil extinction record, Proc. R. Soc. London B, 263, 1605-1610, 1996. [3] M. E. J. Newman and K. Sneppen, Avalanches, scaling, and coherent noise, Phys. Rev. E, 54, 6226-6231, 1996. [4] K. Sneppen and M. Newman, Coherent noise, scale invariance and intermittency in large systems, Physica D, 110, 209 - 222. [5] P. Varotsos, N. Sarlis, and E. Skordas, Spatiotemporal complexity aspects on the interrelation between Seismic Electric Signals and seismicity, Practica of Athens Academy, 76, 294-321, 2001. [6] P.A. Varotsos, N.V. Sarlis, and E.S. Skordas, Long-range correlations in the electric signals that precede rupture, Phys. Rev. E, 66, 011902, 2002. [7] Varotsos P. A., Sarlis N. V. and Skordas E. S., Natural Time Analysis: The new view of time. Precursory Seismic Electric Signals, Earthquakes and other Complex Time-Series (Springer-Verlag, Berlin Heidelberg) 2011. [8] N. V. Sarlis and S.-R. G. Christopoulos, "Visualization of the significance of Receiver Operating Characteristics based on confidence ellipses", Computer Physics Communications, http://dx.doi.org/10.1016/j.cpc.2013.12.009

  11. A semi-analytical model for the prediction of underwater noise from offshore pile driving

    NASA Astrophysics Data System (ADS)

    Tsouvalas, A.; Metrikine, A. V.

    2013-06-01

    Underwater noise from offshore pile driving gained considerable attention in recent years mainly due to the large scale construction of offshore wind farms. The most common foundation type of a wind turbine is a monopile, upon which the wind tower rests. The pile is driven into place with the help of hydraulic hammers. During the hammering of the pile, high levels of noise are generated which are known to produce deleterious effects on both mammals and fish. In this work, a linear semi-analytical model is developed for predicting the levels of underwater noise for a wide range of system parameters. The model incorporates all major parts of the system. The hydraulic hammer is substituted by an external force, the pile is described as a thin circular cylindrical shell, the water is modelled as a compressible fluid and the water-saturated seabed is defined by distributed springs and dashpots in all directions. The solution of the coupled vibroacoustic problem is based on the representation of the response of the complete system on the modal basis of the in vacuo shell structure. The influence that the inter-modal coupling, the choice of the soil parameters and the acoustic impedance of the seabed have on the generated noise levels is studied in the frequency domain. Strong and weak points of the present model are discussed on the basis of a comparison with a set of available experimental data. The obtained results show the capability of the model to predict the underwater noise levels both qualitatively and quantitatively.

  12. Propulsion Airframe Aeroacoustic Integration Effects for a Hybrid Wing Body Aircraft Configuration

    NASA Technical Reports Server (NTRS)

    Czech, Michael J.; Thomas, Russell H.; Elkoby, Ronen

    2010-01-01

    An extensive experimental investigation was performed to study the propulsion airframe aeroacoustic effects of a high bypass ratio engine for a hybrid wing body aircraft configuration where the engine is installed above the wing. The objective was to provide an understanding of the jet noise shielding effectiveness as a function of engine gas condition and location as well as nozzle configuration. A 4.7% scale nozzle of a bypass ratio seven engine was run at characteristic cycle points under static and forward flight conditions. The effect of the pylon and its orientation on jet noise was also studied as a function of bypass ratio and cycle condition. The addition of a pylon yielded significant spectral changes lowering jet noise by up to 4dB at high polar angles and increasing it by 2 to 3dB at forward angles. In order to assess jet noise shielding, a planform representation of the airframe model, also at 4.7% scale was traversed relative to the jet nozzle from downstream to several diameters upstream of the wing trailing edge. Installations at two fan diameters upstream of the wing trailing edge provided only limited shielding in the forward arc at high frequencies for both the axisymmetric and a conventional round nozzle with pylon. This was consistent with phased array measurements suggesting that the high frequency sources are predominantly located near the nozzle exit and, consequently, are amenable to shielding. The mid to low frequencies sources were observed further downstream and shielding was insignificant. Chevrons were designed and used to impact the distribution of sources with the more aggressive design showing a significant upstream migration of the sources in the mid frequency range. Furthermore, the chevrons reduced the low frequency source levels and the typical high frequency increase due to the application of chevron nozzles was successfully shielded. The pylon was further modified with a technology that injects air through the shelf of the

  13. Integration of Propulsion-Airframe-Aeroacoustic Technologies and Design Concepts for a Quiet Blended-Wing-Body Transport

    NASA Technical Reports Server (NTRS)

    Hill, G. A.; Brown, S. A.; Geiselhart, K. A.

    2004-01-01

    This paper summarizes the results of studies undertaken to investigate revolutionary propulsion-airframe configurations that have the potential to achieve significant noise reductions over present-day commercial transport aircraft. Using a 300 passenger Blended-Wing-Body (BWB) as a baseline, several alternative low-noise propulsion-airframe-aeroacoustic (PAA) technologies and design concepts were investigated both for their potential to reduce the overall BWB noise levels, and for their impact on the weight, performance, and cost of the vehicle. Two evaluation frameworks were implemented for the assessments. The first was a Multi-Attribute Decision Making (MADM) process that used a Pugh Evaluation Matrix coupled with the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS). This process provided a qualitative evaluation of the PAA technologies and design concepts and ranked them based on how well they satisfied chosen design requirements. From the results of the evaluation, it was observed that almost all of the PAA concepts gave the BWB a noise benefit, but degraded its performance. The second evaluation framework involved both deterministic and probabilistic systems analyses that were performed on a down-selected number of BWB propulsion configurations incorporating the PAA technologies and design concepts. These configurations included embedded engines with Boundary Layer Ingesting Inlets, Distributed Exhaust Nozzles installed on podded engines, a High Aspect Ratio Rectangular Nozzle, Distributed Propulsion, and a fixed and retractable aft airframe extension. The systems analyses focused on the BWB performance impacts of each concept using the mission range as a measure of merit. Noise effects were also investigated when enough information was available for a tractable analysis. Some tentative conclusions were drawn from the results. One was that the Boundary Layer Ingesting Inlets provided improvements to the BWB's mission range, by

  14. Comparison of methods of predicting community response to impulsive and nonimpulsive noise

    NASA Technical Reports Server (NTRS)

    Fidell, Sanford; Pearsons, Karl S.

    1994-01-01

    Several scientific, regulatory, and policy-coordinating bodies have developed methods for predicting community response to sonic booms. The best known of these is the dosage-response relationship of Working Group 84 of the National Academy of Science's Committee on Hearing, Bioacoustics and Biomechanics. This dosage-response relationship between C-weighted DayNight Average Sound Level and the prevalence of annoyance with high energy impulsive sounds was derived from limited amounts of information about community response to regular, prolonged, and expected exposure to artillery and sonic booms. U.S. Army Regulation 201 adapts this approach to predictions of the acceptability of impulsive noise exposure in communities. This regulation infers equivalent degrees of effect with respect to a well known dosage-response relationship for general (nonimpulsive) transportation noise. Differences in prevalence of annoyance predicted by various relationships lead to different predictions of the compatibility of land uses with sonic boom exposure. An examination of these differences makes apparent several unresolved issues in current practice for predicting and interpreting the prevalence of annoyance due to sonic boom exposure.

  15. Comparison of methods of predicting community response to impulsive and nonimpulsive noise

    NASA Astrophysics Data System (ADS)

    Fidell, Sanford; Pearsons, Karl S.

    1994-02-01

    Several scientific, regulatory, and policy-coordinating bodies have developed methods for predicting community response to sonic booms. The best known of these is the dosage-response relationship of Working Group 84 of the National Academy of Science's Committee on Hearing, Bioacoustics and Biomechanics. This dosage-response relationship between C-weighted DayNight Average Sound Level and the prevalence of annoyance with high energy impulsive sounds was derived from limited amounts of information about community response to regular, prolonged, and expected exposure to artillery and sonic booms. U.S. Army Regulation 201 adapts this approach to predictions of the acceptability of impulsive noise exposure in communities. This regulation infers equivalent degrees of effect with respect to a well known dosage-response relationship for general (nonimpulsive) transportation noise. Differences in prevalence of annoyance predicted by various relationships lead to different predictions of the compatibility of land uses with sonic boom exposure. An examination of these differences makes apparent several unresolved issues in current practice for predicting and interpreting the prevalence of annoyance due to sonic boom exposure.

  16. The significance of parameter uncertainties for the prediction of offshore pile driving noise.

    PubMed

    Lippert, Tristan; von Estorff, Otto

    2014-11-01

    Due to the construction of offshore wind farms and its potential effect on marine wildlife, the numerical prediction of pile driving noise over long ranges has recently gained importance. In this contribution, a coupled finite element/wavenumber integration model for noise prediction is presented and validated by measurements. The ocean environment, especially the sea bottom, can only be characterized with limited accuracy in terms of input parameters for the numerical model at hand. Therefore the effect of these parameter uncertainties on the prediction of sound pressure levels (SPLs) in the water column is investigated by a probabilistic approach. In fact, a variation of the bottom material parameters by means of Monte-Carlo simulations shows significant effects on the predicted SPLs. A sensitivity analysis of the model with respect to the single quantities is performed, as well as a global variation. Based on the latter, the probability distribution of the SPLs at an exemplary receiver position is evaluated and compared to measurements. The aim of this procedure is to develop a model to reliably predict an interval for the SPLs, by quantifying the degree of uncertainty of the SPLs with the MC simulations. PMID:25373948

  17. Highly Variable Cycle Nozzle Concept: Validation of Flow and Noise Predictions

    NASA Technical Reports Server (NTRS)

    Halbig, Michael C.

    2011-01-01

    Results from experimental and numerical studies of highly Variable Cycle (HVC) exhaust model were presented. The model was designed and fabricated under a Supersonics NRA awarded to Rolls-Royce. The model had a lobed mixer for the core stream nozzle, and elliptic fan stream nozzle, and an ejector. Experiments included far-field acoustic array, phased array, and Particle Image Velocimetry (PIV) measurements. Numerical studies included flow simulations using the WIND-US code and far-field acoustic solutions using an acoustic analogy developed by Goldstein (2003) and Leib and Goldstein (2011). Far-field acoustic measurements showed increased noise levels over the round baseline nozzle when using non-static forward flight conditions. Phased array measurements showed noise sources near the ejector doors when tones were produced for small ejector door positions. Ejector door separation identified in the experiments was reproduced in the numerical flow simulations. Acoustic solutions were unable to match levels measured in the peak jet noise direction indicating additional development work is needed to predict noise from highly three-dimensional flows.

  18. SNR Loss: A new objective measure for predicting speech intelligibility of noise-suppressed speech

    PubMed Central

    Ma, Jianfen; Loizou, Philipos C.

    2010-01-01

    Most of the existing intelligibility measures do not account for the distortions present in processed speech, such as those introduced by speech-enhancement algorithms. In the present study, we propose three new objective measures that can be used for prediction of intelligibility of processed (e.g., via an enhancement algorithm) speech in noisy conditions. All three measures use a critical-band spectral representation of the clean and noise-suppressed signals and are based on the measurement of the SNR loss incurred in each critical band after the corrupted signal goes through a speech enhancement algorithm. The proposed measures are flexible in that they can provide different weights to the two types of spectral distortions introduced by enhancement algorithms, namely spectral attenuation and spectral amplification distortions. The proposed measures were evaluated with intelligibility scores obtained by normal-hearing listeners in 72 noisy conditions involving noise-suppressed speech (consonants and sentences) corrupted by four different maskers (car, babble, train and street interferences). Highest correlation (r=−0.85) with sentence recognition scores was obtained using a variant of the SNR loss measure that only included vowel/consonant transitions and weak consonant information. High correlation was maintained for all noise types, with a maximum correlation (r=−0.88) achieved in street noise conditions. PMID:21503274

  19. Design sensitivity analysis of rotorcraft airframe structures for vibration reduction

    NASA Technical Reports Server (NTRS)

    Murthy, T. Sreekanta

    1987-01-01

    Optimization of rotorcraft structures for vibration reduction was studied. The objective of this study is to develop practical computational procedures for structural optimization of airframes subject to steady-state vibration response constraints. One of the key elements of any such computational procedure is design sensitivity analysis. A method for design sensitivity analysis of airframes under vibration response constraints is presented. The mathematical formulation of the method and its implementation as a new solution sequence in MSC/NASTRAN are described. The results of the application of the method to a simple finite element stick model of the AH-1G helicopter airframe are presented and discussed. Selection of design variables that are most likely to bring about changes in the response at specified locations in the airframe is based on consideration of forced response strain energy. Sensitivity coefficients are determined for the selected design variable set. Constraints on the natural frequencies are also included in addition to the constraints on the steady-state response. Sensitivity coefficients for these constraints are determined. Results of the analysis and insights gained in applying the method to the airframe model are discussed. The general nature of future work to be conducted is described.

  20. Airframe Research and Technology for Hypersonic Airbreathing Vehicles

    NASA Technical Reports Server (NTRS)

    Glass, David E.; Merski, N. Ronald; Glass, Christopher E.

    2002-01-01

    The Hypersonics Investment Area (HIA) within NASA's Advanced Space Transportation Program (ASTP) has the responsibility to develop hypersonic airbreathing vehicles for access to space. The Airframe Research and Technology (AR and T) Project, as one of six projects in the HIA, will push the state-of-the-art in airframe and vehicle systems for low-cost, reliable, and safe space transportation. The individual technologies within the project are focused on advanced, breakthrough technologies in airframe and vehicle systems and cross-cutting activities that are the basis for improvements in these disciplines. Both low and medium technology readiness level (TRL) activities are being pursued. The key technical areas that will be addressed by the project include analysis and design tools, integrated vehicle health management (IVHM), composite (polymer, metal, and ceramic matrix) materials development, thermal/structural wall concepts, thermal protection systems, seals, leading edges, aerothermodynamics, and airframe/propulsion flowpath technology. Each of the technical areas or sub-projects within the Airframe R and T Project is described in this paper.

  1. Reducing Propulsion Airframe Aeroacoustic Interactions with Uniquely Tailored Chevrons. 2; Installed Nozzles

    NASA Technical Reports Server (NTRS)

    Mengle, Vinod G.; Elkoby, Ronen; Brusniak, Leon; Thomas, Russ H.

    2006-01-01

    Propulsion airframe aeroacoustic (PAA) interactions arise due to the manner in which an engine is installed on the airframe and lead to an asymmetry in the flow/acoustic environment, for example, for under-the-wing installations due to the pylon, the wing and the high-lift devices. In this work we study how we can affect these PAA interactions to reduce the overall jet-related installed noise by tailoring the chevron shapes on fan and core nozzles in a unique fashion to take advantage of this asymmetry. In part 1 of this trio of papers we introduced the concept of azimuthally varying chevrons (AVC) and showed how some types of AVCs can be more beneficial than the conventional chevrons when tested on "isolated" scaled nozzles inclusive of the pylon effect. In this paper, we continue to study the effect of installing these AVC nozzles under a typical scaled modern wing with high-lift devices placed in a free jet. The noise benefits of these installed nozzles, as well as their installation effects are systematically studied for several fan/core AVC combinations at typical take-off conditions with high bypass ratio. We show, for example, that the top-enhanced mixing T-fan AVC nozzle (with enhanced mixing near the pylon and less mixing away from it) when combined with conventional chevrons on the core nozzle is quieter than conventional chevrons on both nozzles, and hardly produces any high-frequency lift, just as in the isolated case; however, its installed nozzle benefit is less than its isolated nozzle benefit. This suppression of take-off noise benefit under installed conditions, compared to its isolated nozzle benefit, is seen for all other chevron nozzles. We show how these relative noise benefits are related to the relative installation effects of AVCs and baseline nozzles.

  2. Validation of an interior noise prediction model for a composite cylinder

    NASA Technical Reports Server (NTRS)

    Beyer, Todd B.; Grosveld, Ferdinand W.

    1987-01-01

    An acoustic modal analysis has been performed in the cavity of a composite cylinder model of an aircraft fuselage. The filament wound, composite shell is 12 feet long and 5.5 feet in diameter. A one-half-in. thick plywood floor is attached to the shell 69 deg from the vertical centerline through the bottom of the shell. The acoustic modal frequencies were obtained from a sound pressure level and phase survey conducted throughout the interior volume bounded by the floor, endcaps and stiffened shell, while being excited by white noise from a loudspeaker source. The measured acoustic resonance frequencies and mode shapes compare well with analytical predictions from the Propeller Aircraft Interior Noise (PAIN) model. Details of the theory and derivation of the acoustic characteristics have been included. Reverberation time measurements, using the integrated impulse technique, have been performed to determine acoustic loss factors. These measured loss factors have been input to the PAIN program in order to more accurately predict the space-averaged interior noise of the composite cylinder.

  3. Source Methodology for Turbofan Noise Prediction (SOURCE3D Technical Documentation)

    NASA Technical Reports Server (NTRS)

    Meyer, Harold D.

    1999-01-01

    This report provides the analytical documentation for the SOURCE3D Rotor Wake/Stator Interaction Code. It derives the equations for the rotor scattering coefficients and stator source vector and scattering coefficients that are needed for use in the TFANS (Theoretical Fan Noise Design/Prediction System). SOURCE3D treats the rotor and stator as isolated source elements. TFANS uses this information, along with scattering coefficients for inlet and exit elements, and provides complete noise solutions for turbofan engines. SOURCE3D is composed of a collection of FORTRAN programs that have been obtained by extending the approach of the earlier V072 Rotor Wake/Stator Interaction Code. Similar to V072, it treats the rotor and stator as a collection of blades and vanes having zero thickness and camber contained in an infinite, hardwall annular duct. SOURCE3D adds important features to the V072 capability-a rotor element, swirl flow and vorticity waves, actuator disks for flow turning, and combined rotor/actuator disk and stator/actuator disk elements. These items allow reflections from the rotor, frequency scattering, and mode trapping, thus providing more complete noise predictions than previously. The code has been thoroughly verified through comparison with D.B. Hanson's CUP2D two- dimensional code using a narrow annulus test case.

  4. Analytical prediction of break-out noise from a reactive rectangular plenum with four flexible walls.

    PubMed

    Venkatesham, B; Tiwari, Mayank; Munjal, M L

    2010-10-01

    This paper describes an analytical calculation of break-out noise from a rectangular plenum with four flexible walls by incorporating three-dimensional effects along with the acoustical and structural wave coupling phenomena. The breakout noise from rectangular plenums is important and the coupling between acoustic waves within the plenum and structural waves in the flexible plenum walls plays a critical role in prediction of the transverse transmission loss. The first step in breakout noise prediction is to calculate the inside plenum pressure field and the normal flexible plenum wall vibration by using an impedance-mobility approach, which results in a compact matrix formulation. In the impedance-mobility compact matrix (IMCM) approach, it is presumed that the coupled response can be described in terms of finite sets of the uncoupled acoustic subsystem and the structural subsystem. The flexible walls of the plenum are modeled as an unfolded plate to calculate natural frequencies and mode shapes of the uncoupled structural subsystem. The second step is to calculate the radiated sound power from the flexible walls using Kirchhoff-Helmholtz (KH) integral formulation. Analytical results are validated with finite element and boundary element (FEM-BEM) numerical models. PMID:20968352

  5. Rotor Wake/Stator Interaction Noise Prediction Code Technical Documentation and User's Manual

    NASA Technical Reports Server (NTRS)

    Topol, David A.; Mathews, Douglas C.

    2010-01-01

    This report documents the improvements and enhancements made by Pratt & Whitney to two NASA programs which together will calculate noise from a rotor wake/stator interaction. The code is a combination of subroutines from two NASA programs with many new features added by Pratt & Whitney. To do a calculation V072 first uses a semi-empirical wake prediction to calculate the rotor wake characteristics at the stator leading edge. Results from the wake model are then automatically input into a rotor wake/stator interaction analytical noise prediction routine which calculates inlet aft sound power levels for the blade-passage-frequency tones and their harmonics, along with the complex radial mode amplitudes. The code allows for a noise calculation to be performed for a compressor rotor wake/stator interaction, a fan wake/FEGV interaction, or a fan wake/core stator interaction. This report is split into two parts, the first part discusses the technical documentation of the program as improved by Pratt & Whitney. The second part is a user's manual which describes how input files are created and how the code is run.

  6. Sentence Recognition Prediction for Hearing-impaired Listeners in Stationary and Fluctuation Noise With FADE

    PubMed Central

    Schädler, Marc René; Warzybok, Anna; Meyer, Bernd T.; Brand, Thomas

    2016-01-01

    To characterize the individual patient’s hearing impairment as obtained with the matrix sentence recognition test, a simulation Framework for Auditory Discrimination Experiments (FADE) is extended here using the Attenuation and Distortion (A+D) approach by Plomp as a blueprint for setting the individual processing parameters. FADE has been shown to predict the outcome of both speech recognition tests and psychoacoustic experiments based on simulations using an automatic speech recognition system requiring only few assumptions. It builds on the closed-set matrix sentence recognition test which is advantageous for testing individual speech recognition in a way comparable across languages. Individual predictions of speech recognition thresholds in stationary and in fluctuating noise were derived using the audiogram and an estimate of the internal level uncertainty for modeling the individual Plomp curves fitted to the data with the Attenuation (A-) and Distortion (D-) parameters of the Plomp approach. The “typical” audiogram shapes from Bisgaard et al with or without a “typical” level uncertainty and the individual data were used for individual predictions. As a result, the individualization of the level uncertainty was found to be more important than the exact shape of the individual audiogram to accurately model the outcome of the German Matrix test in stationary or fluctuating noise for listeners with hearing impairment. The prediction accuracy of the individualized approach also outperforms the (modified) Speech Intelligibility Index approach which is based on the individual threshold data only. PMID:27604782

  7. Prediction of high-speed rotor noise with a Kirchhoff formula

    NASA Technical Reports Server (NTRS)

    Purcell, Timothy W.; Strawn, Roger C.; Yu, Yung H.

    1987-01-01

    A new methodology has been developed to predict the impulsive noise generated by a transonic rotor blade. The formulation uses a full-potential finite-difference method to obtain the pressure field close to the blade. A Kirchhoff integral formulation is then used to extend these finite-difference results into the far-field. This Kirchhoff formula is written in a blade-fixed coordinate system. It requires initial data across a plane at the sonic radius. This data is provided by the finite-difference solution. Acoustic pressure predictions show excellent agreement with hover experimental data for two hover cases of 0.88 and 0.90 tip Mach number, the latter of which has delocalized transonic flow. These results represent the first successful prediction technique for peak pressure amplitudes using a computational code.

  8. Predicted and measured boundary layer refraction for advanced turboprop propeller noise

    NASA Technical Reports Server (NTRS)

    Dittmar, James H.; Krejsa, Eugene A.

    1990-01-01

    Currently, boundary layer refraction presents a limitation to the measurement of forward arc propeller noise measured on an acoustic plate in the NASA Lewis 8- by 6-Foot Supersonic Wind Tunnel. The use of a validated boundary layer refraction model to adjust the data could remove this limitation. An existing boundary layer refraction model is used to predict the refraction for cases where boundary layer refraction was measured. In general, the model exhibits the same qualitative behavior as the measured refraction. However, the prediction method does not show quantitative agreement with the data. In general, it overpredicts the amount of refraction for the far forward angles at axial Mach number of 0.85 and 0.80 and underpredicts the refraction at axial Mach numbers of 0.75 and 0.70. A more complete propeller source description is suggested as a way to improve the prediction method.

  9. Predicting the Inflow Distortion Tone Noise of the NASA Glenn Advanced Noise Control Fan with a Combined Quadrupole-Dipole Model

    NASA Technical Reports Server (NTRS)

    Koch, L. Danielle

    2012-01-01

    A combined quadrupole-dipole model of fan inflow distortion tone noise has been extended to calculate tone sound power levels generated by obstructions arranged in circumferentially asymmetric locations upstream of a rotor. Trends in calculated sound power level agreed well with measurements from tests conducted in 2007 in the NASA Glenn Advanced Noise Control Fan. Calculated values of sound power levels radiated upstream were demonstrated to be sensitive to the accuracy of the modeled wakes from the cylindrical rods that were placed upstream of the fan to distort the inflow. Results indicate a continued need to obtain accurate aerodynamic predictions and measurements at the fan inlet plane as engineers work towards developing fan inflow distortion tone noise prediction tools.

  10. Emerging Community Noise Reduction Approaches

    NASA Technical Reports Server (NTRS)

    Envia, Edmane

    2012-01-01

    An overview of the current NASA research portfolio in the area of aircraft noise reduction is presented. The emphasis of the research described herein is on meeting the aggressive near- and mid-term national goals for reducing aircraft noise emissions, which NASA internal studies have shown to be feasible using noise reduction technologies currently being developed in-house or in partnership with NASA s industry and academic partners. While NASA has an active research effort in airframe noise reduction, this overview focuses on propulsion noise reduction only.

  11. Isolated Open Rotor Noise Prediction Assessment Using the F31A31 Historical Blade Set

    NASA Technical Reports Server (NTRS)

    Nark, Douglas M.; Jones, William T.; Boyd, D. Douglas, Jr.; Zawodny, Nikolas S.

    2016-01-01

    In an effort to mitigate next-generation fuel efficiency and environmental impact concerns for aviation, open rotor propulsion systems have received renewed interest. However, maintaining the high propulsive efficiency while simultaneously meeting noise goals has been one of the challenges in making open rotor propulsion a viable option. Improvements in prediction tools and design methodologies have opened the design space for next generation open rotor designs that satisfy these challenging objectives. As such, validation of aerodynamic and acoustic prediction tools has been an important aspect of open rotor research efforts. This paper describes validation efforts of a combined computational fluid dynamics and Ffowcs Williams and Hawkings equation methodology for open rotor aeroacoustic modeling. Performance and acoustic predictions were made for a benchmark open rotor blade set and compared with measurements over a range of rotor speeds and observer angles. Overall, the results indicate that the computational approach is acceptable for assessing low-noise open rotor designs. Additionally, this approach may be used to provide realistic incident source fields for acoustic shielding/scattering studies on various aircraft configurations.

  12. 14 CFR 43.7 - Persons authorized to approve aircraft, airframes, aircraft engines, propellers, appliances, or...

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ..., airframes, aircraft engines, propellers, appliances, or component parts for return to service after..., propellers, appliances, or component parts for return to service after maintenance, preventive maintenance... Administrator, may approve an aircraft, airframe, aircraft engine, propeller, appliance, or component part...

  13. 14 CFR 43.7 - Persons authorized to approve aircraft, airframes, aircraft engines, propellers, appliances, or...

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ..., airframes, aircraft engines, propellers, appliances, or component parts for return to service after..., propellers, appliances, or component parts for return to service after maintenance, preventive maintenance... Administrator, may approve an aircraft, airframe, aircraft engine, propeller, appliance, or component part...

  14. 14 CFR 43.7 - Persons authorized to approve aircraft, airframes, aircraft engines, propellers, appliances, or...

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ..., airframes, aircraft engines, propellers, appliances, or component parts for return to service after..., propellers, appliances, or component parts for return to service after maintenance, preventive maintenance... Administrator, may approve an aircraft, airframe, aircraft engine, propeller, appliance, or component part...

  15. 14 CFR 43.7 - Persons authorized to approve aircraft, airframes, aircraft engines, propellers, appliances, or...

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ..., airframes, aircraft engines, propellers, appliances, or component parts for return to service after..., propellers, appliances, or component parts for return to service after maintenance, preventive maintenance... Administrator, may approve an aircraft, airframe, aircraft engine, propeller, appliance, or component part...

  16. 14 CFR 43.7 - Persons authorized to approve aircraft, airframes, aircraft engines, propellers, appliances, or...

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ..., airframes, aircraft engines, propellers, appliances, or component parts for return to service after..., propellers, appliances, or component parts for return to service after maintenance, preventive maintenance... Administrator, may approve an aircraft, airframe, aircraft engine, propeller, appliance, or component part...

  17. Development of computer program ENMASK for prediction of residual environmental masking-noise spectra, from any three independent environmental parameters

    SciTech Connect

    Chang, Y.-S.; Liebich, R. E.; Chun, K. C.

    2000-03-31

    Residual environmental sound can mask intrusive4 (unwanted) sound. It is a factor that can affect noise impacts and must be considered both in noise-impact studies and in noise-mitigation designs. Models for quantitative prediction of sensation level (audibility) and psychological effects of intrusive noise require an input with 1/3 octave-band spectral resolution of environmental masking noise. However, the majority of published residual environmental masking-noise data are given with either octave-band frequency resolution or only single A-weighted decibel values. A model has been developed that enables estimation of 1/3 octave-band residual environmental masking-noise spectra and relates certain environmental parameters to A-weighted sound level. This model provides a correlation among three environmental conditions: measured residual A-weighted sound-pressure level, proximity to a major roadway, and population density. Cited field-study data were used to compute the most probable 1/3 octave-band sound-pressure spectrum corresponding to any selected one of these three inputs. In turn, such spectra can be used as an input to models for prediction of noise impacts. This paper discusses specific algorithms included in the newly developed computer program ENMASK. In addition, the relative audibility of the environmental masking-noise spectra at different A-weighted sound levels is discussed, which is determined by using the methodology of program ENAUDIBL.

  18. A Landing Gear Noise Reduction Study Based on Computational Simulations

    NASA Technical Reports Server (NTRS)

    Khorrami, Mehdi R.; Lockard, David P.

    2006-01-01

    Landing gear is one of the more prominent airframe noise sources. Techniques that diminish gear noise and suppress its radiation to the ground are highly desirable. Using a hybrid computational approach, this paper investigates the noise reduction potential of devices added to a simplified main landing gear model without small scale geometric details. The Ffowcs Williams and Hawkings equation is used to predict the noise at far-field observer locations from surface pressure data provided by unsteady CFD calculations. Because of the simplified nature of the model, most of the flow unsteadiness is restricted to low frequencies. The wheels, gear boxes, and oleo appear to be the primary sources of unsteadiness at these frequencies. The addition of fairings around the gear boxes and wheels, and the attachment of a splitter plate on the downstream side of the oleo significantly reduces the noise over a wide range of frequencies, but a dramatic increase in noise is observed at one frequency. The increased flow velocities, a consequence of the more streamlined bodies, appear to generate extra unsteadiness around other parts giving rise to the additional noise. Nonetheless, the calculations demonstrate the capability of the devices to improve overall landing gear noise.

  19. The Prediction of Broadband Shock-Associated Noise Including Propagation Effects

    NASA Technical Reports Server (NTRS)

    Miller, Steven; Morris, Philip J.

    2011-01-01

    An acoustic analogy is developed based on the Euler equations for broadband shock- associated noise (BBSAN) that directly incorporates the vector Green's function of the linearized Euler equations and a steady Reynolds-Averaged Navier-Stokes solution (SRANS) as the mean flow. The vector Green's function allows the BBSAN propagation through the jet shear layer to be determined. The large-scale coherent turbulence is modeled by two-point second order velocity cross-correlations. Turbulent length and time scales are related to the turbulent kinetic energy and dissipation. An adjoint vector Green's function solver is implemented to determine the vector Green's function based on a locally parallel mean flow at streamwise locations of the SRANS solution. However, the developed acoustic analogy could easily be based on any adjoint vector Green's function solver, such as one that makes no assumptions about the mean flow. The newly developed acoustic analogy can be simplified to one that uses the Green's function associated with the Helmholtz equation, which is consistent with the formulation of Morris and Miller (AIAAJ 2010). A large number of predictions are generated using three different nozzles over a wide range of fully expanded Mach numbers and jet stagnation temperatures. These predictions are compared with experimental data from multiple jet noise labs. In addition, two models for the so-called 'fine-scale' mixing noise are included in the comparisons. Improved BBSAN predictions are obtained relative to other models that do not include the propagation effects, especially in the upstream direction of the jet.

  20. Investigation of a panel code for airframe/propeller integration analyses

    NASA Technical Reports Server (NTRS)

    Miley, S. J.

    1982-01-01

    The Hess panel code was investigated as a procedure to predict the aerodynamic loading associated with propeller slipstream interference on the airframe. The slipstream was modeled as a variable onset flow to the lifting and nonlifting bodies treated by the code. Four sets of experimental data were used for comparisons with the code. The results indicate that the Hess code, in its present form, will give valid solutions for nonuniform onset flows which vary in direction only. The code presently gives incorrect solutions for flows with variations in velocity. Modifications to the code to correct this are discussed.

  1. Analytical prediction of the interior noise for cylindrical models of aircraft fuselages for prescribed exterior noise fields. Phase 1: Development and validation of preliminary analytical models

    NASA Technical Reports Server (NTRS)

    Pope, L. D.; Rennison, D. C.; Wilby, E. G.

    1980-01-01

    The basic theoretical work required to understand sound transmission into an enclosed space (that is, one closed by the transmitting structure) is developed for random pressure fields and for harmonic (tonal) excitation. The analysis is used to predict the noise reducton of unpressurized unstiffened cylinder, and also the interior response of the cylinder given a tonal (plane wave) excitation. Predictions and measurements are compared and the transmission is analyzed. In addition, results for tonal (harmonic) mechanical excitation are considered.

  2. Vortical gust boundary condition for realistic rotor wake/stator interaction noise prediction using computational aeroacoustics

    NASA Astrophysics Data System (ADS)

    Hixon, Ray; Sescu, Adrian; Sawyer, Scott

    2011-08-01

    In this work, the NASA Glenn Research Center Broadband Aeroacoustic Stator Simulation (BASS) code is extended for use in the prediction of noise produced by realistic three-dimensional rotor wakes impinging on a downstream stator row. In order to accurately simulate such a flow using a nonlinear time-accurate solver, the inflow and outflow boundary conditions must simultaneously maintain the desired mean flow, allow outgoing vortical, entropic, and acoustic waves to cleanly exit the domain, and accurately impose the desired incoming flow disturbances. This work validates a new method for the acoustics-free imposition of three-dimensional vortical disturbances using benchmark test cases.

  3. Dual-band infrared imaging to detect corrosion damage within airframes and concrete structures

    SciTech Connect

    Del Grande, N.K.; Durbin, P.F.

    1994-01-01

    We are developing dual-band infrared (DBIR) imaging and detection techniques to inspect air frames and concrete bridge decks for hidden corrosion damage. Using selective DBIR image ratios,, we enhanced surface temperature contrast and removed surface emissivity noise associated with clutter. Our surface temperature maps depicted defect sites, which heat and cool at different rates than their surroundings. Our emissivity-ratio maps tagged and removed the masking effects of surface clutter. For airframe inspections, we used time-resolved DBIR temperature, emissivity-ratio and composite thermal inertia maps to locate corrosion-thinning effects within a flash-heated Boeing 737 airframe. Emissivity-ratio maps tagged and removed clutter sites from uneven paint, dirt and surface markers. Temperature and thermal inertia maps characterized defect sites, types, sizes, thicknesses, thermal properties and material-loss effects from air frame corrosion. For concrete inspections, we mapped DBIR temperature and emissivity-ratio patterns to better interpret surrogate delamination sites within naturally-heated, concrete slabs and remove the clutter mask from sand pile-up, grease stains, rocks and other surface objects.

  4. Liner Optimization Studies Using the Ducted Fan Noise Prediction Code TBIEM3D

    NASA Technical Reports Server (NTRS)

    Dunn, M. H.; Farassat, F.

    1998-01-01

    In this paper we demonstrate the usefulness of the ducted fan noise prediction code TBIEM3D as a liner optimization design tool. Boundary conditions on the interior duct wall allow for hard walls or a locally reacting liner with axially segmented, circumferentially uniform impedance. Two liner optimization studies are considered in which farfield noise attenuation due to the presence of a liner is maximized by adjusting the liner impedance. In the first example, the dependence of optimal liner impedance on frequency and liner length is examined. Results show that both the optimal impedance and attenuation levels are significantly influenced by liner length and frequency. In the second example, TBIEM3D is used to compare radiated sound pressure levels between optimal and non-optimal liner cases at conditions designed to simulate take-off. It is shown that significant noise reduction is achieved for most of the sound field by selecting the optimal or near optimal liner impedance. Our results also indicate that there is relatively large region of the impedance plane over which optimal or near optimal liner behavior is attainable. This is an important conclusion for the designer since there are variations in liner characteristics due to manufacturing imprecisions.

  5. TBIEM3D: A Computer Program for Predicting Ducted Fan Engine Noise. Version 1.1

    NASA Technical Reports Server (NTRS)

    Dunn, M. H.

    1997-01-01

    This document describes the usage of the ducted fan noise prediction program TBIEM3D (Thin duct - Boundary Integral Equation Method - 3 Dimensional). A scattering approach is adopted in which the acoustic pressure field is split into known incident and unknown scattered parts. The scattering of fan-generated noise by a finite length circular cylinder in a uniform flow field is considered. The fan noise is modeled by a collection of spinning point thrust dipoles. The program, based on a Boundary Integral Equation Method (BIEM), calculates circumferential modal coefficients of the acoustic pressure at user-specified field locations. The duct interior can be of the hard wall type or lined. The duct liner is axisymmetric, locally reactive, and can be uniform or axially segmented. TBIEM3D is written in the FORTRAN programming language. Input to TBIEM3D is minimal and consists of geometric and kinematic parameters. Discretization and numerical parameters are determined automatically by the code. Several examples are presented to demonstrate TBIEM3D capabilities.

  6. Ambient seismic noise monitoring of a clay landslide: Toward failure prediction

    NASA Astrophysics Data System (ADS)

    Mainsant, Guénolé; Larose, Eric; Brönnimann, Cornelia; Jongmans, Denis; Michoud, Clément; Jaboyedoff, Michel

    2012-03-01

    Given that clay-rich landslides may become mobilized, leading to rapid mass movements (earthflows and debris flows), they pose critical problems in risk management worldwide. The most widely proposed mechanism leading to such flow-like movements is the increase in water pore pressure in the sliding mass, generating partial or complete liquefaction. This solid-to-liquid transition results in a dramatic reduction of mechanical rigidity in the liquefied zones, which could be detected by monitoring shear wave velocity variations. With this purpose in mind, the ambient seismic noise correlation technique has been applied to measure the variation in the seismic surface wave velocity in the Pont Bourquin landslide (Swiss Alps). This small but active composite earthslide-earthflow was equipped with continuously recording seismic sensors during spring and summer 2010. An earthslide of a few thousand cubic meters was triggered in mid-August 2010, after a rainy period. This article shows that the seismic velocity of the sliding material, measured from daily noise correlograms, decreased continuously and rapidly for several days prior to the catastrophic event. From a spectral analysis of the velocity decrease, it was possible to determine the location of the change at the base of the sliding layer. These results demonstrate that ambient seismic noise can be used to detect rigidity variations before failure and could potentially be used to predict landslides.

  7. Propulsion Airframe Aeroacoustics Technology Evaluation and Selection Using a Multi-Attribute Decision Making Process and Non-Deterministic Design

    NASA Technical Reports Server (NTRS)

    Burg, Cecile M.; Hill, Geoffrey A.; Brown, Sherilyn A.; Geiselhart, Karl A.

    2004-01-01

    The Systems Analysis Branch at NASA Langley Research Center has investigated revolutionary Propulsion Airframe Aeroacoustics (PAA) technologies and configurations for a Blended-Wing-Body (BWB) type aircraft as part of its research for NASA s Quiet Aircraft Technology (QAT) Project. Within the context of the long-term NASA goal of reducing the perceived aircraft noise level by a factor of 4 relative to 1997 state of the art, major configuration changes in the propulsion airframe integration system were explored with noise as a primary design consideration. An initial down-select and assessment of candidate PAA technologies for the BWB was performed using a Multi-Attribute Decision Making (MADM) process consisting of organized brainstorming and decision-making tools. The assessments focused on what effect the PAA technologies had on both the overall noise level of the BWB and what effect they had on other major design considerations such as weight, performance and cost. A probabilistic systems analysis of the PAA configurations that presented the best noise reductions with the least negative impact on the system was then performed. Detailed results from the MADM study and the probabilistic systems analysis will be published in the near future.

  8. Development of nonlinear acoustic propagation analysis tool toward realization of loud noise environment prediction in aeronautics

    NASA Astrophysics Data System (ADS)

    Kanamori, Masashi; Takahashi, Takashi; Aoyama, Takashi

    2015-10-01

    Shown in this paper is an introduction of a prediction tool for the propagation of loud noise with the application to the aeronautics in mind. The tool, named SPnoise, is based on HOWARD approach, which can express almost exact multidimensionality of the diffraction effect at the cost of back scattering. This paper argues, in particular, the prediction of the effect of atmospheric turbulence on sonic boom as one of the important issues in aeronautics. Thanks to the simple and efficient modeling of the atmospheric turbulence, SPnoise successfully re-creates the feature of the effect, which often emerges in the region just behind the front and rear shock waves in the sonic boom signature.

  9. Development of nonlinear acoustic propagation analysis tool toward realization of loud noise environment prediction in aeronautics

    SciTech Connect

    Kanamori, Masashi Takahashi, Takashi Aoyama, Takashi

    2015-10-28

    Shown in this paper is an introduction of a prediction tool for the propagation of loud noise with the application to the aeronautics in mind. The tool, named SPnoise, is based on HOWARD approach, which can express almost exact multidimensionality of the diffraction effect at the cost of back scattering. This paper argues, in particular, the prediction of the effect of atmospheric turbulence on sonic boom as one of the important issues in aeronautics. Thanks to the simple and efficient modeling of the atmospheric turbulence, SPnoise successfully re-creates the feature of the effect, which often emerges in the region just behind the front and rear shock waves in the sonic boom signature.

  10. Broadband Fan Noise Prediction System for Turbofan Engines. Volume 1; Setup_BFaNS User's Manual and Developer's Guide

    NASA Technical Reports Server (NTRS)

    Morin, Bruce L.

    2010-01-01

    Pratt & Whitney has developed a Broadband Fan Noise Prediction System (BFaNS) for turbofan engines. This system computes the noise generated by turbulence impinging on the leading edges of the fan and fan exit guide vane, and noise generated by boundary-layer turbulence passing over the fan trailing edge. BFaNS has been validated on three fan rigs that were tested during the NASA Advanced Subsonic Technology Program (AST). The predicted noise spectra agreed well with measured data. The predicted effects of fan speed, vane count, and vane sweep also agreed well with measurements. The noise prediction system consists of two computer programs: Setup_BFaNS and BFaNS. Setup_BFaNS converts user-specified geometry and flow-field information into a BFaNS input file. From this input file, BFaNS computes the inlet and aft broadband sound power spectra generated by the fan and FEGV. The output file from BFaNS contains the inlet, aft and total sound power spectra from each noise source. This report is the first volume of a three-volume set documenting the Broadband Fan Noise Prediction System: Volume 1: Setup_BFaNS User s Manual and Developer s Guide; Volume 2: BFaNS User's Manual and Developer s Guide; and Volume 3: Validation and Test Cases. The present volume begins with an overview of the Broadband Fan Noise Prediction System, followed by step-by-step instructions for installing and running Setup_BFaNS. It concludes with technical documentation of the Setup_BFaNS computer program.

  11. Broadband Fan Noise Prediction System for Turbofan Engines. Volume 2; BFaNS User's Manual and Developer's Guide

    NASA Technical Reports Server (NTRS)

    Morin, Bruce L.

    2010-01-01

    Pratt & Whitney has developed a Broadband Fan Noise Prediction System (BFaNS) for turbofan engines. This system computes the noise generated by turbulence impinging on the leading edges of the fan and fan exit guide vane, and noise generated by boundary-layer turbulence passing over the fan trailing edge. BFaNS has been validated on three fan rigs that were tested during the NASA Advanced Subsonic Technology Program (AST). The predicted noise spectra agreed well with measured data. The predicted effects of fan speed, vane count, and vane sweep also agreed well with measurements. The noise prediction system consists of two computer programs: Setup_BFaNS and BFaNS. Setup_BFaNS converts user-specified geometry and flow-field information into a BFaNS input file. From this input file, BFaNS computes the inlet and aft broadband sound power spectra generated by the fan and FEGV. The output file from BFaNS contains the inlet, aft and total sound power spectra from each noise source. This report is the second volume of a three-volume set documenting the Broadband Fan Noise Prediction System: Volume 1: Setup_BFaNS User s Manual and Developer s Guide; Volume 2: BFaNS User s Manual and Developer s Guide; and Volume 3: Validation and Test Cases. The present volume begins with an overview of the Broadband Fan Noise Prediction System, followed by step-by-step instructions for installing and running BFaNS. It concludes with technical documentation of the BFaNS computer program.

  12. Acoustic Noise Prediction of the Amine Swingbed ISS ExPRESS Rack Payload

    NASA Technical Reports Server (NTRS)

    Welsh, David; Smith, Holly; Wang, Shuo

    2010-01-01

    Acoustics plays a vital role in maintaining the health, safety, and comfort of crew members aboard the International Space Station (ISS). In order to maintain this livable and workable environment, acoustic requirements have been established to ensure that ISS hardware and payload developers account for the acoustic emissions of their equipment and develop acoustic mitigations as necessary. These requirements are verified by an acoustic emissions test of the integrated hardware. The Amine Swingbed ExPRESS (Expedite the PRocessing of ExperimentS to Space) rack payload creates a unique challenge to the developers in that the payload hardware is transported to the ISS in phases, making an acoustic emissions test on the integrated flight hardware impossible. In addition, the payload incorporates a high back pressure fan and a diaphragm vacuum pump, which are recognized as significant and complex noise sources. In order to accurately predict the acoustic emissions of the integrated payload, the individual acoustic noise sources and paths are first characterized. These characterizations are conducted though a series of acoustic emissions tests on the individual payload components. Secondly, the individual acoustic noise sources and paths are incorporated into a virtual model of the integrated hardware. The virtual model is constructed with the use of hybrid method utilizing the Finite Element Acoustic (FEA) and Statistical Energy Analysis (SEA) techniques, which predict the overall acoustic emissions. Finally, the acoustic model is validated though an acoustic characterization test performed on an acoustically similar mock-up of the flight unit. The results of the validated acoustic model are then used to assess the acoustic emissions of the flight unit and define further acoustic mitigation efforts.

  13. Computation of interactional aerodynamics for noise prediction of heavy lift rotorcraft

    NASA Astrophysics Data System (ADS)

    Hennes, Christopher C.

    Many computational tools are used when developing a modern helicopter. As the design space is narrowed, more accurate and time-intensive tools are brought to bear. These tools are used to determine the effect of a design decision on the performance, handling, stability and efficiency of the aircraft. One notable parameter left out of this process is acoustics. This is due in part to the difficulty in making useful acoustics calculations that reveal the differences between various design configurations. This thesis presents a new approach designed to bridge the gap in prediction capability between fast but low-fidelity Lagrangian particle methods, and slow but high-fidelity Eulerian computational fluid dynamics simulations. A multi-pronged approach is presented. First, a simple flow solver using well-understood and tested flow solution methodologies is developed specifically to handle bodies in arbitrary motion. To this basic flow solver two new technologies are added. The first is an Immersed Boundary technique designed to be tolerant of geometric degeneracies and low-resolution grids. This new technique allows easy inclusion of complex fuselage geometries at minimal computational cost, improving the ability of a solver to capture the complex interactional aerodynamic effects expected in modern rotorcraft design. The second new technique is an extension of a concept from flow visualization where the motion of tip vortices are tracked through the solution using massless particles convecting with the local flow. In this extension of that concept, the particles maintain knowledge of the expected and actual vortex strength. As a post-processing step, when the acoustic calculations are made, these particles are used to augment the loading noise calculation and reproduce the highly-impulsive character of blade-vortex interaction noise. In combination these new techniques yield a significant improvement to the state of the art in rotorcraft blade-vortex interaction noise

  14. Computational Structures Technology for Airframes and Propulsion Systems

    NASA Technical Reports Server (NTRS)

    Noor, Ahmed K. (Compiler); Housner, Jerrold M. (Compiler); Starnes, James H., Jr. (Compiler); Hopkins, Dale A. (Compiler); Chamis, Christos C. (Compiler)

    1992-01-01

    This conference publication contains the presentations and discussions from the joint University of Virginia (UVA)/NASA Workshops. The presentations included NASA Headquarters perspectives on High Speed Civil Transport (HSCT), goals and objectives of the UVA Center for Computational Structures Technology (CST), NASA and Air Force CST activities, CST activities for airframes and propulsion systems in industry, and CST activities at Sandia National Laboratory.

  15. Airframe technology for aircraft energy efficiency. [economic factors

    NASA Technical Reports Server (NTRS)

    James, R. L., Jr.; Maddalon, D. V.

    1984-01-01

    The economic factors that resulted in the implementation of the aircraft energy efficiency program (ACEE) are reviewed and airframe technology elements including content, progress, applications, and future direction are discussed. The program includes the development of laminar flow systems, advanced aerodynamics, active controls, and composite structures.

  16. Design of an integrated airframe/propulsion control system architecture

    NASA Technical Reports Server (NTRS)

    Cohen, Gerald C.; Lee, C. William; Strickland, Michael J.; Torkelson, Thomas C.

    1990-01-01

    The design of an integrated airframe/propulsion control system architecture is described. The design is based on a prevalidation methodology that uses both reliability and performance. A detailed account is given for the testing associated with a subset of the architecture and concludes with general observations of applying the methodology to the architecture.

  17. Novel inlet-airframe integration methodology for hypersonic waverider vehicles

    NASA Astrophysics Data System (ADS)

    Ding, Feng; Liu, Jun; Shen, Chi-bing; Huang, Wei

    2015-06-01

    With the aim of integrating a ramjet or scramjet with an airframe, a novel inlet-airframe integration methodology for the hypersonic waverider vehicle is proposed. For this newly proposed design concept and for the specified flight conditions, not only the forebody of the vehicle but also its engine cowl and wings can ride on the bow shock wave, causing the bow shock wave to remain attached to the leading edge for the entire length of the vehicle. Thus, this integrated vehicle can take full advantage of the waverider's high lift-to-drag ratio characteristics and the ideal pre-compression surface for the engine. In this work, a novel inlet-airframe integrated axisymmetric basic flow model that accounts for both external and internal flows is first designed using the method of characteristics and the streamline tracing technique. Subsequently, the design of the inlet-airframe integrated waverider vehicle is generated from the integrated axisymmetric basic flow model using the streamline tracing technique. Then, the design methodologies of both the integrated axisymmetric basic flow model and the integrated waverider vehicle are verified by a computational numerical method. Finally, the viscous effects and performance of both the integrated axisymmetric basic flow model and the integrated waverider vehicle are analysed under the design condition using the numerical computation. The obtained results show that the proposed approach is effective in designing the integrated hypersonic waverider vehicle.

  18. The estimation technique of the airframe design for manufacturability

    NASA Astrophysics Data System (ADS)

    Govorkov, A.; Zhilyaev, A.

    2016-04-01

    This paper discusses the method of quantitative estimation of a design for manufacturability of the parts of the airframe. The method is based on the interaction of individual indicators considering the weighting factor. The authors of the paper introduce the algorithm of the design for manufacturability of parts based on its 3D model

  19. Aviation Maintenance Technology. Airframe. A204. Aircraft Welding. Instructor Material.

    ERIC Educational Resources Information Center

    Oklahoma State Board of Vocational and Technical Education, Stillwater. Curriculum and Instructional Materials Center.

    This teacher's guide is designed to aid teachers in leading students through a module on aircraft welding on airframes. The module contains four units that cover the following topics: (1) gas welding and cutting; (2) brazing and soldering; (3) shielded metal arc welding; and (4) gas tungsten arc welding. Each unit follows a standardized format…

  20. IMPAC: An Integrated Methodology for Propulsion and Airframe Control

    NASA Technical Reports Server (NTRS)

    Garg, Sanjay; Ouzts, Peter J.; Lorenzo, Carl F.; Mattern, Duane L.

    1991-01-01

    The National Aeronautics and Space Administration is actively involved in the development of enabling technologies that will lead towards aircraft with new/enhanced maneuver capabilities such as Short Take-Off Vertical Landing (STOVL) and high angle of attack performance. Because of the high degree of dynamic coupling between the airframe and propulsion systems of these types of aircraft, one key technology is the integration of the flight and propulsion control. The NASA Lewis Research Center approach to developing Integrated Flight Propulsion Control (IFPC) technologies is an in-house research program referred to as IMPAC (Integrated Methodology for Propulsion and Airframe Control). The goals of IMPAC are to develop a viable alternative to the existing integrated control design methodologies that will allow for improved system performance and simplicity of control law synthesis and implementation, and to demonstrate the applicability of the methodology to a supersonic STOVL fighter aircraft. Based on some preliminary control design studies that included evaluation of the existing methodologies, the IFPC design methodology that is emerging at the Lewis Research Center consists of considering the airframe and propulsion system as one integrated system for an initial centralized controller design and then partitioning the centralized controller into separate airframe and propulsion system subcontrollers to ease implementation and to set meaningful design requirements for detailed subsystem control design and evaluation. An overview of IMPAC is provided and detailed discussion of the various important design and evaluation steps in the methodology are included.

  1. The Usability of Noise Level from Rock Cutting for the Prediction of Physico-Mechanical Properties of Rocks

    NASA Astrophysics Data System (ADS)

    Delibalta, M. S.; Kahraman, S.; Comakli, R.

    2015-11-01

    Because the indirect tests are easier and cheaper than the direct tests, the prediction of rock properties from the indirect testing methods is important especially for the preliminary investigations. In this study, the predictability of the physico-mechanical rock properties from the noise level measured during cutting rock with diamond saw was investigated. Noise measurement test, uniaxial compressive strength (UCS) test, Brazilian tensile strength (BTS) test, point load strength (Is) test, density test, and porosity test were carried out on 54 different rock types in the laboratory. The results were statistically analyzed to derive estimation equations. Strong correlations between the noise level and the mechanical rock properties were found. The relations follow power functions. Increasing rock strength increases the noise level. Density and porosity also correlated strongly with the noise level. The relations follow linear functions. Increasing density increases the noise level while increasing porosity decreases the noise level. The developed equations are valid for the rocks with a compressive strength below 150 MPa. Concluding remark is that the physico-mechanical rock properties can reliably be estimated from the noise level measured during cutting the rock with diamond saw.

  2. Assessment of Radiated Fan Noise Prediction Capabilities Using Static Engine Test Data

    NASA Technical Reports Server (NTRS)

    Nark, Douglas M.

    2011-01-01

    This paper describes further assessment of the CDUCT-LaRC code via comparison with static engine test data. In an effort to improve confidence in the use of CDUCT-LaRC for liner optimization studies addressing realistic three-dimensional geometries, inlet radiated fan noise predictions were performed at 54% and 87% engine speed settings. Predictions were then compared with far-field measurements to assess the approach and implementation. The particular configurations were chosen to exercise the three-dimensional capability of CDUCT-LaRC and it s applicability to realistic configurations and conditions. At the 54% engine speed setting, the predictions capture the general directivity and acoustic treatment effects quite well. Comparisons of the predicted and measured directivity at the 87% power setting were more problematic. This was likely due in part to the difficulties in source specification and possibly the nonlinear nature of buzz-saw tones at this engine operating condition. Overall, the approach captured the basic trends and provided a conservative estimate of liner effects from which relative performance metrics could be inferred.

  3. Assessment of Geometry and In-Flow Effects on Contra-Rotating Open Rotor Broadband Noise Predictions

    NASA Technical Reports Server (NTRS)

    Zawodny, Nikolas S.; Nark, Douglas M.; Boyd, D. Douglas, Jr.

    2015-01-01

    Application of previously formulated semi-analytical models for the prediction of broadband noise due to turbulent rotor wake interactions and rotor blade trailing edges is performed on the historical baseline F31/A31 contra-rotating open rotor configuration. Simplified two-dimensional blade element analysis is performed on cambered NACA 4-digit airfoil profiles, which are meant to serve as substitutes for the actual rotor blade sectional geometries. Rotor in-flow effects such as induced axial and tangential velocities are incorporated into the noise prediction models based on supporting computational fluid dynamics (CFD) results and simplified in-flow velocity models. Emphasis is placed on the development of simplified rotor in-flow models for the purpose of performing accurate noise predictions independent of CFD information. The broadband predictions are found to compare favorably with experimental acoustic results.

  4. The Effects of Noise on Speech Recognition in Cochlear Implant Subjects: Predictions and Analysis Using Acoustic Models

    NASA Astrophysics Data System (ADS)

    Remus, Jeremiah J.; Collins, Leslie M.

    2005-12-01

    Cochlear implants can provide partial restoration of hearing, even with limited spectral resolution and loss of fine temporal structure, to severely deafened individuals. Studies have indicated that background noise has significant deleterious effects on the speech recognition performance of cochlear implant patients. This study investigates the effects of noise on speech recognition using acoustic models of two cochlear implant speech processors and several predictive signal-processing-based analyses. The results of a listening test for vowel and consonant recognition in noise are presented and analyzed using the rate of phonemic feature transmission for each acoustic model. Three methods for predicting patterns of consonant and vowel confusion that are based on signal processing techniques calculating a quantitative difference between speech tokens are developed and tested using the listening test results. Results of the listening test and confusion predictions are discussed in terms of comparisons between acoustic models and confusion prediction performance.

  5. Large Eddy Simulation of Airfoil Self-Noise at High Reynolds Number

    NASA Astrophysics Data System (ADS)

    Kocheemoolayil, Joseph; Lele, Sanjiva

    2015-11-01

    The trailing edge noise section (Category 1) of the Benchmark Problems for Airframe Noise Computations (BANC) workshop features five canonical problems. No first-principles based approach free of empiricism and tunable coefficients has successfully predicted trailing edge noise for the five configurations to date. Our simulations predict trailing edge noise accurately for all five configurations. The simulation database is described in detail, highlighting efforts undertaken to validate the results through systematic comparison with dedicated experiments and establish insensitivity to grid resolution, domain size, alleatory uncertainties such as the tripping mechanism used to force transition to turbulence and epistemic uncertainties such as models for unresolved near-wall turbulence. Ongoing efforts to extend the predictive capability to non-canonical configurations featuring flow separation are summarized. A novel, large-span calculation that predicts the flow past a wind turbine airfoil in deep stall with unprecedented accuracy is presented. The simulations predict airfoil noise in the near-stall regime accurately. While the post-stall noise predictions leave room for improvement, significant uncertainties in the experiment might preclude a fair comparison in this regime. We thank Cascade Technologies Inc. for providing access to the CharLES toolkit - a massively-parallel, unstructured large eddy simulation framework.

  6. TFaNS Tone Fan Noise Design/Prediction System. Volume 2; User's Manual; 1.4

    NASA Technical Reports Server (NTRS)

    Topol, David A.; Eversman, Walter

    1999-01-01

    TFaNS is the Tone Fan Noise Design/Prediction System developed by Pratt & Whitney under contract to NASA Lewis (presently NASA Glenn). The purpose of this system is to predict tone noise emanating from a fan stage including the effects of reflection and transmission by the rotor and stator and by the duct inlet and nozzle. These effects have been added to an existing annular duct/isolated stator noise prediction capability. TFaNS consists of: the codes that compute the acoustic properties (reflection and transmission coefficients) of the various elements and write them to files. CUP3D: Fan Noise Coupling Code that reads these files, solves the coupling problem, and outputs the desired noise predictions. AWAKEN: CFD/Measured Wake Postprocessor which reformats CFD wake predictions and/or measured wake data so it can be used by the system. This volume of the report provides information on code input and file structure essential for potential users of TFANS. This report is divided into three volumes: Volume 1. System Description, CUP3D Technical Documentation, and Manual for Code Developers; Volume 2. User's Manual, TFANS Vers. 1.4; Volume 3. Evaluation of System Codes.

  7. Prediction of the spectrum of atmospheric microburst noise in the range 2-20 Hz - Preliminary results

    NASA Technical Reports Server (NTRS)

    Hardin, Jay C.; Pope, D. Stuart

    1989-01-01

    An engineering estimate of the spectrum of atmospheric microburst noise radiation in the range 2-20 Hz is developed. This prediction is obtained via a marriage of standard aeroacoustic theory with a numerical computation of the relevant fluid dynamics. The 'computational aeroacoustics' technique applied here to the interpretation of atmospheric noise measurements is illustrative of a methodology that can now be employed in a wide class of problems.

  8. Effects of Physiological Internal Noise on Model Predictions of Concurrent Vowel Identification for Normal-Hearing Listeners.

    PubMed

    Hedrick, Mark S; Moon, Il Joon; Woo, Jihwan; Won, Jong Ho

    2016-01-01

    Previous studies have shown that concurrent vowel identification improves with increasing temporal onset asynchrony of the vowels, even if the vowels have the same fundamental frequency. The current study investigated the possible underlying neural processing involved in concurrent vowel perception. The individual vowel stimuli from a previously published study were used as inputs for a phenomenological auditory-nerve (AN) model. Spectrotemporal representations of simulated neural excitation patterns were constructed (i.e., neurograms) and then matched quantitatively with the neurograms of the single vowels using the Neurogram Similarity Index Measure (NSIM). A novel computational decision model was used to predict concurrent vowel identification. To facilitate optimum matches between the model predictions and the behavioral human data, internal noise was added at either neurogram generation or neurogram matching using the NSIM procedure. The best fit to the behavioral data was achieved with a signal-to-noise ratio (SNR) of 8 dB for internal noise added at the neurogram but with a much smaller amount of internal noise (SNR of 60 dB) for internal noise added at the level of the NSIM computations. The results suggest that accurate modeling of concurrent vowel data from listeners with normal hearing may partly depend on internal noise and where internal noise is hypothesized to occur during the concurrent vowel identification process. PMID:26866811

  9. Information-bearing acoustic change outperforms duration in predicting intelligibility of full-spectrum and noise-vocoded sentences.

    PubMed

    Stilp, Christian E

    2014-03-01

    Recent research has demonstrated a strong relationship between information-bearing acoustic changes in the speech signal and speech intelligibility. The availability of information-bearing acoustic changes reliably predicts intelligibility of full-spectrum [Stilp and Kluender (2010). Proc. Natl. Acad. Sci. U.S.A. 107(27), 12387-12392] and noise-vocoded sentences amid noise interruption [Stilp et al. (2013). J. Acoust. Soc. Am. 133(2), EL136-EL141]. However, other research reports that proportion of signal duration preserved also predicts intelligibility of noise-interrupted speech. These factors have only ever been investigated independently, obscuring whether one better explains speech perception. The present experiments manipulated both factors to answer this question. A broad range of sentence durations (160-480 ms) containing high or low information-bearing acoustic changes were replaced by speech-shaped noise in noise-vocoded (Experiment 1) and full-spectrum sentences (Experiment 2). Sentence intelligibility worsened with increasing noise replacement, but in both experiments, information-bearing acoustic change was a statistically superior predictor of performance. Perception relied more heavily on information-bearing acoustic changes in poorer listening conditions (in spectrally degraded sentences and amid increasing noise replacement). Highly linear relationships between measures of information and performance suggest that exploiting information-bearing acoustic change is a shared principle underlying perception of acoustically rich and degraded speech. Results demonstrate the explanatory power of information-theoretic approaches for speech perception.

  10. Effects of Physiological Internal Noise on Model Predictions of Concurrent Vowel Identification for Normal-Hearing Listeners

    PubMed Central

    Woo, Jihwan; Won, Jong Ho

    2016-01-01

    Previous studies have shown that concurrent vowel identification improves with increasing temporal onset asynchrony of the vowels, even if the vowels have the same fundamental frequency. The current study investigated the possible underlying neural processing involved in concurrent vowel perception. The individual vowel stimuli from a previously published study were used as inputs for a phenomenological auditory-nerve (AN) model. Spectrotemporal representations of simulated neural excitation patterns were constructed (i.e., neurograms) and then matched quantitatively with the neurograms of the single vowels using the Neurogram Similarity Index Measure (NSIM). A novel computational decision model was used to predict concurrent vowel identification. To facilitate optimum matches between the model predictions and the behavioral human data, internal noise was added at either neurogram generation or neurogram matching using the NSIM procedure. The best fit to the behavioral data was achieved with a signal-to-noise ratio (SNR) of 8 dB for internal noise added at the neurogram but with a much smaller amount of internal noise (SNR of 60 dB) for internal noise added at the level of the NSIM computations. The results suggest that accurate modeling of concurrent vowel data from listeners with normal hearing may partly depend on internal noise and where internal noise is hypothesized to occur during the concurrent vowel identification process. PMID:26866811

  11. Effects of Physiological Internal Noise on Model Predictions of Concurrent Vowel Identification for Normal-Hearing Listeners.

    PubMed

    Hedrick, Mark S; Moon, Il Joon; Woo, Jihwan; Won, Jong Ho

    2016-01-01

    Previous studies have shown that concurrent vowel identification improves with increasing temporal onset asynchrony of the vowels, even if the vowels have the same fundamental frequency. The current study investigated the possible underlying neural processing involved in concurrent vowel perception. The individual vowel stimuli from a previously published study were used as inputs for a phenomenological auditory-nerve (AN) model. Spectrotemporal representations of simulated neural excitation patterns were constructed (i.e., neurograms) and then matched quantitatively with the neurograms of the single vowels using the Neurogram Similarity Index Measure (NSIM). A novel computational decision model was used to predict concurrent vowel identification. To facilitate optimum matches between the model predictions and the behavioral human data, internal noise was added at either neurogram generation or neurogram matching using the NSIM procedure. The best fit to the behavioral data was achieved with a signal-to-noise ratio (SNR) of 8 dB for internal noise added at the neurogram but with a much smaller amount of internal noise (SNR of 60 dB) for internal noise added at the level of the NSIM computations. The results suggest that accurate modeling of concurrent vowel data from listeners with normal hearing may partly depend on internal noise and where internal noise is hypothesized to occur during the concurrent vowel identification process.

  12. A moving medium formulation for prediction of propeller noise at incidence

    NASA Astrophysics Data System (ADS)

    Ghorbaniasl, Ghader; Lacor, Chris

    2012-01-01

    This paper presents a time domain formulation for the sound field radiated by moving bodies in a uniform steady flow with arbitrary orientation. The aim is to provide a formulation for prediction of noise from body so that effects of crossflow on a propeller can be modeled in the time domain. An established theory of noise generation by a moving source is combined with the moving medium Green's function for derivation of the formulation. A formula with Doppler factor is developed because it is more easily interpreted and is more helpful in examining the physic of systems. Based on the technique presented, the source of asymmetry of the sound field can be explained in terms of physics of a moving source. It is shown that the derived formulation can be interpreted as an extension of formulation 1 and 1A of Farassat based on the Ffowcs Williams and Hawkings (FW-H) equation for moving medium problems. Computational results for a stationary monopole and dipole point source in moving medium, a rotating point force in crossflow, a model of helicopter blade at incidence and a propeller case with subsonic tips at incidence verify the formulation.

  13. Large-eddy simulation for the prediction of supersonic rectangular jet noise

    NASA Astrophysics Data System (ADS)

    Nichols, Joseph W.; Ham, Frank E.; Lele, Sanjiva K.; Bridges, James E.

    2011-11-01

    We investigate the noise from isothermal and heated under-expanded supersonic turbulent jets issuing from a rectangular nozzle of aspect ratio 4:1 using high-fidelity unstructured large-eddy simulation (LES) and acoustic projection based on the Ffowcs-Williams Hawkings (FWH) equations. The nozzle/flow interaction is directly included by simulating the flow in and around the nozzle in addition to the jet plume downstream. A grid resolution study is performed and results are shown for unstructured meshes containing up to 300 million control volumes, generated by a massively parallel code scaled to as many as 65,536 processors. Validated against laboratory measurements using a nozzle of precisely the same geometry, we find that mesh isotropy is a key factor in determining the quality of the far-field aeroacoustic predictions. The full flow fields produced by the simulation, in conjunction with particle image velocimetry (PIV) data measured from experiment, allow for a detailed examination of the interaction of large-scale coherent flow features and the resultant far-field noise, and its subsequent modification in the presence of heating. Supported by NASA grant NNX07AC94A and PSAAP, with computational resources from a DoD HPCMP CAP-2 project.

  14. Noise prediction of a subsonic turbulent round jet using the lattice-Boltzmann method

    PubMed Central

    Lew, Phoi-Tack; Mongeau, Luc; Lyrintzis, Anastasios

    2010-01-01

    The lattice-Boltzmann method (LBM) was used to study the far-field noise generated from a Mach, Mj=0.4, unheated turbulent axisymmetric jet. A commercial code based on the LBM kernel was used to simulate the turbulent flow exhausting from a pipe which is 10 jet radii in length. Near-field flow results such as jet centerline velocity decay rates and turbulence intensities were in agreement with experimental results and results from comparable LES studies. The predicted far field sound pressure levels were within 2 dB from published experimental results. Weak unphysical tones were present at high frequency in the computed radiated sound pressure spectra. These tones are believed to be due to spurious sound wave reflections at boundaries between regions of varying voxel resolution. These “VR tones” did not appear to bias the underlying broadband noise spectrum, and they did not affect the overall levels significantly. The LBM appears to be a viable approach, comparable in accuracy to large eddy simulations, for the problem considered. The main advantages of this approach over Navier–Stokes based finite difference schemes may be a reduced computational cost, ease of including the nozzle in the computational domain, and ease of investigating nozzles with complex shapes. PMID:20815448

  15. Prediction of far-field wind turbine noise propagation with parabolic equation.

    PubMed

    Lee, Seongkyu; Lee, Dongjai; Honhoff, Saskia

    2016-08-01

    Sound propagation of wind farms is typically simulated by the use of engineering tools that are neglecting some atmospheric conditions and terrain effects. Wind and temperature profiles, however, can affect the propagation of sound and thus the perceived sound in the far field. A better understanding and application of those effects would allow a more optimized farm operation towards meeting noise regulations and optimizing energy yield. This paper presents the parabolic equation (PE) model development for accurate wind turbine noise propagation. The model is validated against analytic solutions for a uniform sound speed profile, benchmark problems for nonuniform sound speed profiles, and field sound test data for real environmental acoustics. It is shown that PE provides good agreement with the measured data, except upwind propagation cases in which turbulence scattering is important. Finally, the PE model uses computational fluid dynamics results as input to accurately predict sound propagation for complex flows such as wake flows. It is demonstrated that wake flows significantly modify the sound propagation characteristics.

  16. The Prediction of Ducted Fan Engine Noise Via a Boundary Integral Equation Method

    NASA Technical Reports Server (NTRS)

    Farassat, F.; Dunn, M. H.; Tweed, J.

    1996-01-01

    A computationally efficient Boundary Integral Equation Method (BIEM) for the prediction of ducted fan engine noise is presented. The key features of the BIEM are its versatility and the ability to compute rapidly any portion of the sound field without the need to compute the entire field. Governing equations for the BIEM are based on the assumptions that all acoustic processes are linear, generate spinning modes, and occur in a uniform flow field. An exterior boundary value problem (BVP) is defined that describes the scattering of incident sound by an engine duct with arbitrary profile. Boundary conditions on the duct walls are derived that allow for passive noise control treatment. The BVP is recast as a system of hypersingular boundary integral equations for the unknown duct surface quantities. BIEM solution methodology is demonstrated for the scattering of incident sound by a thin cylindrical duct with hard walls. Numerical studies are conducted for various engine parameters and continuous portions of the total pressure field are computed. Radiation and duct propagation results obtained are in agreement with the classical results of spinning mode theory for infinite ducts.

  17. Prediction of far-field wind turbine noise propagation with parabolic equation.

    PubMed

    Lee, Seongkyu; Lee, Dongjai; Honhoff, Saskia

    2016-08-01

    Sound propagation of wind farms is typically simulated by the use of engineering tools that are neglecting some atmospheric conditions and terrain effects. Wind and temperature profiles, however, can affect the propagation of sound and thus the perceived sound in the far field. A better understanding and application of those effects would allow a more optimized farm operation towards meeting noise regulations and optimizing energy yield. This paper presents the parabolic equation (PE) model development for accurate wind turbine noise propagation. The model is validated against analytic solutions for a uniform sound speed profile, benchmark problems for nonuniform sound speed profiles, and field sound test data for real environmental acoustics. It is shown that PE provides good agreement with the measured data, except upwind propagation cases in which turbulence scattering is important. Finally, the PE model uses computational fluid dynamics results as input to accurately predict sound propagation for complex flows such as wake flows. It is demonstrated that wake flows significantly modify the sound propagation characteristics. PMID:27586709

  18. A reduced-scale railway noise barrier's insertion loss and absorption coefficients: comparison of field measurements and predictions

    NASA Astrophysics Data System (ADS)

    Busch, T. A.; Nugent, R. E.

    2003-10-01

    In situ testing determined the insertion loss ( IL) and absorption coefficients of a candidate absorptive noise barrier (soundwall) to abate railway noise for residents of Anaheim, CA. A 4000 m barrier is proposed south of the tracks, but residential areas to the north have expressed concerns that barrier reflections will increase their noise exposure. To address these concerns, a 3.66 m high by 14.6 m long demonstration barrier was built in the parking lot of Edison Field, Anaheim, as part of a public open house, thereby allowing for acoustical measurements. Insertion loss ( IL) was measured in third-octave bands assuming 1/2-scale construction. The IL for three, scaled railway noise sub-sources (rail/wheel interface, locomotive, and train horn) was measured at six, scaled distances. The highest total, A-weighted IL, after corrections for finite-barrier and point-source speaker effects was 22 dB(A) for rail/wheel noise, 18 dB(A) for locomotive noise, and 20 dB(A) for train horn noise. These results can be compared favourably to IL predictions made using algorithms from the US Federal Rail Administration (FRA) noise assessment guidelines. For the actual barrier installation, shielded residential receivers located south of the project are expected to see their future noise exposures reduced from an unmitigated 78 CNEL to 65 CNEL. Absorption coefficients were measured using time delay spectrometry. At lower frequencies, measured absorption coefficients were notably less than the reverberation room results advertised in the manufacturer's literature, but generally conformed with impedance tube results. At higher frequencies the correspondence between measured absorption coefficients and reverberation room results was much improved. For the actual barrier installation, unshielded residential receivers to the north are expected to experience noise exposure increases of less than 1 dB(A). This factor of increase is consistent with a finding of no impact when assessed

  19. Combustion noise

    NASA Technical Reports Server (NTRS)

    Strahle, W. C.

    1977-01-01

    A review of the subject of combustion generated noise is presented. Combustion noise is an important noise source in industrial furnaces and process heaters, turbopropulsion and gas turbine systems, flaring operations, Diesel engines, and rocket engines. The state-of-the-art in combustion noise importance, understanding, prediction and scaling is presented for these systems. The fundamentals and available theories of combustion noise are given. Controversies in the field are discussed and recommendations for future research are made.

  20. The Prediction of Noise Scattered by a Wing/Ducted Fan Configuration

    NASA Technical Reports Server (NTRS)

    Tweed, John; Dunn, Mark H.

    1999-01-01

    In this proof of concept research, a computational method was developed for predicting the sound field created by the scattering of ducted fan engine noise by a blended wing-body (BWB). It was assumed that all acoustic processes were linear and time harmonic with excitation frequency co. Inflow effects were neglected and no penetration boundary conditions were applied to the engine nacelle and BWB surfaces. A scattering approach was adopted in which the total acoustic field is written as the sum of known incident (from the engine duct) and unknown scattered parts. We further assume that the incident field is independent of the scattered field. Application of the above conditions to the equations of linearized acoustics yields the Helmholtz equation (reduced wave equation) for the scattered pressure with Neumann boundary conditions.

  1. Correlation of AH-1G airframe flight vibration data with a coupled rotor-fuselage analysis

    NASA Technical Reports Server (NTRS)

    Sangha, K.; Shamie, J.

    1990-01-01

    The formulation and features of the Rotor-Airframe Comprehensive Analysis Program (RACAP) is described. The analysis employs a frequency domain, transfer matrix approach for the blade structural model, a time domain wake or momentum theory aerodynamic model, and impedance matching for rotor-fuselage coupling. The analysis is applied to the AH-1G helicopter, and a correlation study is conducted on fuselage vibration predictions. The purpose of the study is to evaluate the state-of-the-art in helicopter fuselage vibration prediction technology. The fuselage vibration predicted using RACAP are fairly good in the vertical direction and somewhat deficient in the lateral/longitudinal directions. Some of these deficiencies are traced to the fuselage finite element model.

  2. A coherent model for predicting noise reduction in long enclosures with impedance discontinuities

    NASA Astrophysics Data System (ADS)

    Lam, P. M.; Li, K. M.

    2007-01-01

    A theoretical model has been developed for the prediction of sound propagation in a rectangular long enclosure with impedance discontinuities. Based on the image-source method, the boundaries are assumed to be geometrically reflective. An infinite number of image sources are generated by multiple reflections. The sound pressure of each image is obtained by an approximate analytical solution, known as the Weyl-van der Pol formula. The total sound field is then calculated by summation of the contribution from all images. The phase information of each image and the phase change upon reflection are included in the model. A single change of impedance in a two-dimensional duct is focused on as the fundamental problem of the current study. The diffraction effect at the impedance discontinuity is proved to be insignificant, and it is ignored in the formulation. On the assumption that the diffraction effect is not important, the investigation is moved on to a rectangular long enclosure. Measurements are conducted in two model tunnels to validate the proposed prediction model. The predictions are found to give good approximations of the experimental results. The theoretical model serves as the first attempt to optimize the position and pattern of sound absorption materials in a long enclosure, such as an underground railway station or a building corridor, for the reduction of noise and improvement of sound quality.

  3. A Rapid Distortion Theory modified turbulence spectra for semi-analytical airfoil noise prediction

    NASA Astrophysics Data System (ADS)

    Santana, Leandro D.; Christophe, Julien; Schram, Christophe; Desmet, Wim

    2016-11-01

    This paper proposes an implementation of the Rapid Distortion Theory, for the prediction of the noise resulting from the interaction of an airfoil with incoming turbulence. In the framework of the semi-analytical modeling strategy known as Amiet's theory, this interaction mechanism is treated in a linearized form where the airfoil thickness, camber and angle of attack are assumed negligible, leading to a frozen turbulence description of the incident gust. Important semi-analytical developments have been proposed in the literature to improve the modeling of the gust-airfoil interaction accounting for parallel and skewed gusts, non-rectangular linearized airfoil shapes or blade tip effects. This work is rather focused on the investigation of the distortion of turbulence that occurs in the vicinity of the airfoil leading edge, compared with Rapid Distortion Theory, where main results are briefly reminded in this paper. The main contribution of this work is a detailed experimental investigation of the evolution of turbulent quantities relevant to noise production, performed in the close vicinity of the airfoil leading edge subjected to grid turbulence, by means of stereoscopic Particle Image Velocimetry measurements. The results indicate that the distortion effects are concentrated in a narrow region close to the stagnation point of the leading edge, with dimension of the order of its radius of curvature. Additionally, it is shown that the turbulence intensity grows significantly as the flow approaches the airfoil leading-edge. Based on those results, a modified turbulence spectrum is proposed to describe the incoming turbulence in Amiet's theory. The sound predictions show a significantly better match with acoustic measurements than using the original turbulence model.

  4. PROPOSAL OF PREDICTIVE EQUATIONS FOR THE SOUND PRESSURE SPECTRUM LEVEL OF THE BLAST NOISE IN THE TUNNEL

    NASA Astrophysics Data System (ADS)

    Ishida, Shigeki; Kakigi, Hiroya; Shinji, Masato

    The noise reduction effect of a sound insulation door installed in a tunnel under construction can be analyzed practically by the numerical analysis using the SEA method. However there was a problem that the prediction analysis is quite difficult at the planning stage because there was not the predictive technique of the sound pressure spectrum level(SPSL) of blast noise to be necessary as input data. In this Study, We analyzed relationship between gunpowder quantity and frequency domain damping characteristic of the sound pressure level in the tunnel based on field measurement results. And based on this analysis, we propose a predictive equation for the SPSL of the blast noise in the tunnel, and discuss its applicability.

  5. Methods and Tools for Monitoring and Prediction of the Large-Scale Environmental Impact of Railway Noise

    NASA Astrophysics Data System (ADS)

    ELBERS, F. B. J.

    2000-03-01

    Due to environmental impact regulations there is a demand for methods and tools to determine noise reception levels near railway lines. Currently, a wide variety of methods and tools is available. Fast computers now enable us to develop powerful tools that combine simplified prediction methods with GIS systems. These new systems allow the study of noise reception levels and environmental impact on a large-scale (complete network, national or international), while more detailed and labour-intensive methods and tools are used when demanded by law. This paper presents a brief overview of the noise prediction methods and tools used in the Netherlands. The focus is on the advantages and restrictions of the different methods. Finally, the paper gives an overview of the actual advantages and restrictions of the recently extended Gerano method Gerano98 (Geographic Railway Noise). Gerano was originally based on the “basic Dutch calculation rules for railway noise”. Gerano98 was extended using simplified prediction schemes for the most relevant parts of the “detailed Dutch calculation rules for railway noise”. This most recent calculation method, combined with geographic input features, provides the possibility of determining noise impact and the noise measures to be taken on both the medium and large scale. Examples of the application of the methods and tools to specific (medium- and large-scale) projects are provided. The medium-scale project presents the results of a selection of the prefered line between Amsterdam and Zwolle. The large-scale project (the complete Dutch railway network) shows the results of the comparison of noise measures at source with noise barriers or housing insulation. For both projects the applicability and the usefulness of the methods in these situations is discussed. In conclusion four developments of the Gerano concept are described which have recently been finished or will be so in the near future.

  6. Advanced general aviation comparative engine/airframe integration study

    NASA Technical Reports Server (NTRS)

    Huggins, G. L.; Ellis, D. R.

    1981-01-01

    The NASA Advanced Aviation Comparative Engine/Airframe Integration Study was initiated to help determine which of four promising concepts for new general aviation engines for the 1990's should be considered for further research funding. The engine concepts included rotary, diesel, spark ignition, and turboprop powerplants; a conventional state-of-the-art piston engine was used as a baseline for the comparison. Computer simulations of the performance of single and twin engine pressurized aircraft designs were used to determine how the various characteristics of each engine interacted in the design process. Comparisons were made of how each engine performed relative to the others when integrated into an airframe and required to fly a transportation mission.

  7. Impact of Noise on a Dynamical System: Prediction and Uncertainties from a Swarm-Optimized Neural Network.

    PubMed

    López-Caraballo, C H; Lazzús, J A; Salfate, I; Rojas, P; Rivera, M; Palma-Chilla, L

    2015-01-01

    An artificial neural network (ANN) based on particle swarm optimization (PSO) was developed for the time series prediction. The hybrid ANN+PSO algorithm was applied on Mackey-Glass chaotic time series in the short-term x(t + 6). The performance prediction was evaluated and compared with other studies available in the literature. Also, we presented properties of the dynamical system via the study of chaotic behaviour obtained from the predicted time series. Next, the hybrid ANN+PSO algorithm was complemented with a Gaussian stochastic procedure (called stochastic hybrid ANN+PSO) in order to obtain a new estimator of the predictions, which also allowed us to compute the uncertainties of predictions for noisy Mackey-Glass chaotic time series. Thus, we studied the impact of noise for several cases with a white noise level (σ(N)) from 0.01 to 0.1. PMID:26351449

  8. Impact of Noise on a Dynamical System: Prediction and Uncertainties from a Swarm-Optimized Neural Network

    PubMed Central

    López-Caraballo, C. H.; Lazzús, J. A.; Salfate, I.; Rojas, P.; Rivera, M.; Palma-Chilla, L.

    2015-01-01

    An artificial neural network (ANN) based on particle swarm optimization (PSO) was developed for the time series prediction. The hybrid ANN+PSO algorithm was applied on Mackey-Glass chaotic time series in the short-term x(t + 6). The performance prediction was evaluated and compared with other studies available in the literature. Also, we presented properties of the dynamical system via the study of chaotic behaviour obtained from the predicted time series. Next, the hybrid ANN+PSO algorithm was complemented with a Gaussian stochastic procedure (called stochastic hybrid ANN+PSO) in order to obtain a new estimator of the predictions, which also allowed us to compute the uncertainties of predictions for noisy Mackey-Glass chaotic time series. Thus, we studied the impact of noise for several cases with a white noise level (σN) from 0.01 to 0.1. PMID:26351449

  9. Advanced general aviation engine/airframe integration study

    NASA Technical Reports Server (NTRS)

    Zmroczek, L. A.

    1982-01-01

    A comparison of the in-airframe performance and efficiency of the advanced engine concepts is presented. The results indicate that the proposed advanced engines can significantly improve the performance and economy of general aviation airplanes. The engine found to be most promising is the highly advanced version of a rotary combustion (Wankel) engine. The low weight and fuel consumption of this engine, as well as its small size, make it suited for aircraft use.

  10. Avionics and airframe options: current usage and future plans.

    PubMed

    Mayfield, T; Cady, G

    1994-01-01

    The 1994 Avionics and Airframe Survey was sent to 178 chief or lead pilots of helicopter emergency medical services (HEMS) programs in October 1993, and 100 (56%) were returned. Sixty-four programs (64%) reported that they operate one helicopter exclusively for EMS, 24 (24%) operate two, and 12 (12%) reported using three or more aircraft. Interestingly, the reported percentage of programs with two or more exclusive helicopters continues to rise, increasing by 5.6% to 36%.

  11. Design of an integrated airframe/propulsion control system architecture

    NASA Technical Reports Server (NTRS)

    Cohen, Gerald C.; Lee, C. William; Strickland, Michael J.

    1990-01-01

    The design of an integrated airframe/propulsion control system architecture is described. The design is based on a prevalidation methodology that used both reliability and performance tools. An account is given of the motivation for the final design and problems associated with both reliability and performance modeling. The appendices contain a listing of the code for both the reliability and performance model used in the design.

  12. Analysis of small crack behavior for airframe applications

    NASA Technical Reports Server (NTRS)

    Mcclung, R. C.; Chan, K. S.; Hudak, S. J., Jr.; Davidson, D. L.

    1994-01-01

    The small fatigue crack problem is critically reviewed from the perspective of airframe applications. Different types of small cracks-microstructural, mechanical, and chemical-are carefully defined and relevant mechanisms identified. Appropriate analysis techniques, including both rigorous scientific and practical engineering treatments, are briefly described. Important materials data issues are addressed, including increased scatter in small crack data and recommended small crack test methods. Key problems requiring further study are highlighted.

  13. NASA Airframe Icing Research Overview Past and Current

    NASA Technical Reports Server (NTRS)

    Potapczuk, Mark

    2009-01-01

    This slide presentation reviews the past and current research that NASA has done in the area of airframe icing. Both the history experimental efforts and model development to understand the process and problem of ice formation are reviewed. This has resulted in the development of new experimental methods, advanced icing simulation software, flight dynamics and experimental databases that have an impact on design, testing, construction and certification and qualification of the aircraft and its sub-systems.

  14. Computational Aeroelastic Modeling of Airframes and TurboMachinery: Progress and Challenges

    NASA Technical Reports Server (NTRS)

    Bartels, R. E.; Sayma, A. I.

    2006-01-01

    Computational analyses such as computational fluid dynamics and computational structural dynamics have made major advances toward maturity as engineering tools. Computational aeroelasticity is the integration of these disciplines. As computational aeroelasticity matures it too finds an increasing role in the design and analysis of aerospace vehicles. This paper presents a survey of the current state of computational aeroelasticity with a discussion of recent research, success and continuing challenges in its progressive integration into multidisciplinary aerospace design. This paper approaches computational aeroelasticity from the perspective of the two main areas of application: airframe and turbomachinery design. An overview will be presented of the different prediction methods used for each field of application. Differing levels of nonlinear modeling will be discussed with insight into accuracy versus complexity and computational requirements. Subjects will include current advanced methods (linear and nonlinear), nonlinear flow models, use of order reduction techniques and future trends in incorporating structural nonlinearity. Examples in which computational aeroelasticity is currently being integrated into the design of airframes and turbomachinery will be presented.

  15. Experimental Analysis of Flow over a Highly Maneuverable Airframe

    NASA Astrophysics Data System (ADS)

    Spirnak, Jonathan; Benson, Michael; van Poppel, Bret; Elkins, Christopher; Eaton, John; Team HMA Team

    2015-11-01

    One way to reduce the collateral damage in war is by increasing the accuracy of indirect fire weapons. The Army Research Laboratory is currently developing a Highly Maneuverable Airframe (HMA) consisting of four deflecting canards to provide in-flight maneuverability while fins maintain short duration aerodynamic stability. An experiment was conducted using Magnetic Resonance Velocimetry (MRV) techniques to gather three dimensional, three-component velocity data for fluid flow over a scaled down HMA model. Tests were performed at an angle of attack of 2.3° and canard deflection angles of 0° and 2°. The resulting data serve to both validate computational fluid dynamics (CFD) simulations and understand the flow over this complex geometry. Particular interest is given to the development of the tip and inboard vortices that originate at the canard/body junction and the canard tips to determine their effects on airframe stability. Results show the development of a strong tip vortex and four weaker inboard vortices off each canard. Although the weaker inboard vortices dissipate rapidly downstream of the canard trailing edges, the stronger tip vortices persist until reaching the fins approximately six chord lengths downstream of the canard trailing edges. Team HMA designed and built the water channel and airframe for this experiment.

  16. Fluidic actuators for active flow control on airframe

    NASA Astrophysics Data System (ADS)

    Schueller, M.; Weigel, P.; Lipowski, M.; Meyer, M.; Schlösser, P.; Bauer, M.

    2016-04-01

    One objective of the European Projects AFLoNext and Clean Sky 2 is to apply Active Flow Control (AFC) on the airframe in critical aerodynamic areas such as the engine/wing junction or the outer wing region for being able to locally improve the aerodynamics in certain flight conditions. At the engine/wing junction, AFC is applied to alleviate or even eliminate flow separation at low speeds and high angle of attacks likely to be associated with the integration of underwing- mounted Ultra High Bypass Ratio (UHBR) engines and the necessary slat-cut-outs. At the outer wing region, AFC can be used to allow more aggressive future wing designs with improved performance. A relevant part of the work on AFC concepts for airframe application is the development of suitable actuators. Fluidic Actuated Flow Control (FAFC) has been introduced as a Flow Control Technology that influences the boundary layer by actively blowing air through slots or holes out of the aircraft skin. FAFC actuators can be classified by their Net Mass Flux and accordingly divided into ZNMF (Zero Net Mass Flux) and NZNMF (Non Zero Net-Mass-Flux) actuators. In the frame of both projects, both types of the FAFC actuator concepts are addressed. In this paper, the objectives of AFC on the airframe is presented and the actuators that are used within the project are discussed.

  17. Validation of finite element computations for the quantitative prediction of underwater noise from impact pile driving.

    PubMed

    Zampolli, Mario; Nijhof, Marten J J; de Jong, Christ A F; Ainslie, Michael A; Jansen, Erwin H W; Quesson, Benoit A J

    2013-01-01

    The acoustic radiation from a pile being driven into the sediment by a sequence of hammer strikes is studied with a linear, axisymmetric, structural acoustic frequency domain finite element model. Each hammer strike results in an impulsive sound that is emitted from the pile and then propagated in the shallow water waveguide. Measurements from accelerometers mounted on the head of a test pile and from hydrophones deployed in the water are used to validate the model results. Transfer functions between the force input at the top of the anvil and field quantities, such as acceleration components in the structure or pressure in the fluid, are computed with the model. These transfer functions are validated using accelerometer or hydrophone measurements to infer the structural forcing. A modeled hammer forcing pulse is used in the successive step to produce quantitative predictions of sound exposure at the hydrophones. The comparison between the model and the measurements shows that, although several simplifying assumptions were made, useful predictions of noise levels based on linear structural acoustic models are possible. In the final part of the paper, the model is used to characterize the pile as an acoustic radiator by analyzing the flow of acoustic energy.

  18. Validation of finite element computations for the quantitative prediction of underwater noise from impact pile driving.

    PubMed

    Zampolli, Mario; Nijhof, Marten J J; de Jong, Christ A F; Ainslie, Michael A; Jansen, Erwin H W; Quesson, Benoit A J

    2013-01-01

    The acoustic radiation from a pile being driven into the sediment by a sequence of hammer strikes is studied with a linear, axisymmetric, structural acoustic frequency domain finite element model. Each hammer strike results in an impulsive sound that is emitted from the pile and then propagated in the shallow water waveguide. Measurements from accelerometers mounted on the head of a test pile and from hydrophones deployed in the water are used to validate the model results. Transfer functions between the force input at the top of the anvil and field quantities, such as acceleration components in the structure or pressure in the fluid, are computed with the model. These transfer functions are validated using accelerometer or hydrophone measurements to infer the structural forcing. A modeled hammer forcing pulse is used in the successive step to produce quantitative predictions of sound exposure at the hydrophones. The comparison between the model and the measurements shows that, although several simplifying assumptions were made, useful predictions of noise levels based on linear structural acoustic models are possible. In the final part of the paper, the model is used to characterize the pile as an acoustic radiator by analyzing the flow of acoustic energy. PMID:23297884

  19. A method for predicting DCT-based denoising efficiency for grayscale images corrupted by AWGN and additive spatially correlated noise

    NASA Astrophysics Data System (ADS)

    Rubel, Aleksey S.; Lukin, Vladimir V.; Egiazarian, Karen O.

    2015-03-01

    Results of denoising based on discrete cosine transform for a wide class of images corrupted by additive noise are obtained. Three types of noise are analyzed: additive white Gaussian noise and additive spatially correlated Gaussian noise with middle and high correlation levels. TID2013 image database and some additional images are taken as test images. Conventional DCT filter and BM3D are used as denoising techniques. Denoising efficiency is described by PSNR and PSNR-HVS-M metrics. Within hard-thresholding denoising mechanism, DCT-spectrum coefficient statistics are used to characterize images and, subsequently, denoising efficiency for them. Results of denoising efficiency are fitted for such statistics and efficient approximations are obtained. It is shown that the obtained approximations provide high accuracy of prediction of denoising efficiency.

  20. Propulsion system noise reduction

    NASA Technical Reports Server (NTRS)

    Feiler, C. E.; Heidelberg, L. J.; Karchmer, A. M.; Lansing, D. L.; Miller, B. A.; Rice, E. J.

    1975-01-01

    The progress in propulsion system noise reduction is reviewed. The noise technology areas discussed include: fan noise; advances in suppression including conventional acoustic treatment, high Mach number inlets, and wing shielding; engine core noise; flap noise from both under-the-wing and over-the-wing powered-lift systems; supersonic jet noise suppression; and the NASA program in noise prediction.

  1. Predictions of Taylor's power law, density dependence and pink noise from a neutrally modeled time series.

    PubMed

    Keil, Petr; Herben, Tomás; Rosindell, James; Storch, David

    2010-07-01

    There has recently been increasing interest in neutral models of biodiversity and their ability to reproduce the patterns observed in nature, such as species abundance distributions. Here we investigate the ability of a neutral model to predict phenomena observed in single-population time series, a study complementary to most existing work that concentrates on snapshots in time of the whole community. We consider tests for density dependence, the dominant frequencies of population fluctuation (spectral density) and a relationship between the mean and variance of a fluctuating population (Taylor's power law). We simulated an archipelago model of a set of interconnected local communities with variable mortality rate, migration rate, speciation rate, size of local community and number of local communities. Our spectral analysis showed 'pink noise': a departure from a standard random walk dynamics in favor of the higher frequency fluctuations which is partly consistent with empirical data. We detected density dependence in local community time series but not in metacommunity time series. The slope of the Taylor's power law in the model was similar to the slopes observed in natural populations, but the fit to the power law was worse. Our observations of pink noise and density dependence can be attributed to the presence of an upper limit to community sizes and to the effect of migration which distorts temporal autocorrelation in local time series. We conclude that some of the phenomena observed in natural time series can emerge from neutral processes, as a result of random zero-sum birth, death and migration. This suggests the neutral model would be a parsimonious null model for future studies of time series data.

  2. Tone Noise Predictions for a Spacecraft Cabin Ventilation Fan Ingesting Distorted Inflow and the Challenges of Validation

    NASA Technical Reports Server (NTRS)

    Koch, L. Danielle; Shook, Tony D.; Astler, Douglas T.; Bittinger, Samantha A.

    2011-01-01

    A fan tone noise prediction code has been developed at NASA Glenn Research Center that is capable of estimating duct mode sound power levels for a fan ingesting distorted inflow. This code was used to predict the circumferential and radial mode sound power levels in the inlet and exhaust duct of an axial spacecraft cabin ventilation fan. Noise predictions at fan design rotational speed were generated. Three fan inflow conditions were studied: an undistorted inflow, a circumferentially symmetric inflow distortion pattern (cylindrical rods inserted radially into the flowpath at 15deg, 135deg, and 255deg), and a circumferentially asymmetric inflow distortion pattern (rods located at 15deg, 52deg and 173deg). Noise predictions indicate that tones are produced for the distorted inflow cases that are not present when the fan operates with an undistorted inflow. Experimental data are needed to validate these acoustic predictions, as well as the aerodynamic performance predictions. Given the aerodynamic design of the spacecraft cabin ventilation fan, a mechanical and electrical conceptual design study was conducted. Design features of a fan suitable for obtaining detailed acoustic and aerodynamic measurements needed to validate predictions are discussed.

  3. Tone Noise Predictions for a Spacecraft Cabin Ventilation Fan Ingesting Distorted Inflow and the Challenges of Validation

    NASA Technical Reports Server (NTRS)

    Koch, L. Danielle; Shook, Tony D.; Astler, Douglas T.; Bittinger, Samantha A.

    2012-01-01

    A fan tone noise prediction code has been developed at NASA Glenn Research Center that is capable of estimating duct mode sound power levels for a fan ingesting distorted inflow. This code was used to predict the circumferential and radial mode sound power levels in the inlet and exhaust duct of an axial spacecraft cabin ventilation fan. Noise predictions at fan design rotational speed were generated. Three fan inflow conditions were studied: an undistorted inflow, a circumferentially symmetric inflow distortion pattern (cylindrical rods inserted radially into the flowpath at 15deg, 135deg, and 255deg), and a circumferentially asymmetric inflow distortion pattern (rods located at 15deg, 52deg and 173deg). Noise predictions indicate that tones are produced for the distorted inflow cases that are not present when the fan operates with an undistorted inflow. Experimental data are needed to validate these acoustic predictions, as well as the aerodynamic performance predictions. Given the aerodynamic design of the spacecraft cabin ventilation fan, a mechanical and electrical conceptual design study was conducted. Design features of a fan suitable for obtaining detailed acoustic and aerodynamic measurements needed to validate predictions are discussed.

  4. Slat tonal noise mechanisms in a two-dimensional multi-element airfoil configuration

    NASA Astrophysics Data System (ADS)

    Olson, Susan Denise

    Airframe noise from commercial aircraft rivals engine noise in the landing phase of flight. Unsteady flow around the leading edge slat of the high-lift system contributes significantly to airframe noise. This research experimentally investigated tonal noise sources arising from the unsteady flow around the leading edge slat from a flow physics standpoint. Using this approach, efficient acoustic control strategies naturally follow. This study resolved two types of acoustic tones, trailing edge vortex shedding noise and acoustic resonance, originating from the slat component of a two-dimensional, three-element airfoil model. The latter noise mechanism had not been documented until the current study. Sharpening the slat trailing edge reduced the overall sound pressure level from the shedding noise by 12dB. The reduction in radiated acoustic pressure was directly proportional to the reduction in the strength of the vortex shedding. The acoustic power was conceptually related to the strength of the global instability in the wake. The onset of the slat aeroacoustic resonance corresponded to the formation of a separation bubble on the upper surface of the slat. The peak acoustic frequency matched the frequency of large-scale structures ejected from the separation bubble. A feedback loop between the near-wake region and the separation point sustained the resonance. A model based on a phase matching condition between the acoustic waves and the generation of the separated shear layer instability waves successfully predicted the acoustic frequencies. The acoustic tone followed the modal variation closest to the subharmonic of the natural instability frequency, which caused the discontinuous jumps in frequency with increasing velocity.

  5. Elastomeric Structural Attachment Concepts for Aircraft Flap Noise Reduction - Challenges and Approaches to Hyperelastic Structural Modeling and Analysis

    NASA Technical Reports Server (NTRS)

    Sreekantamurthy, Thammaiah; Turner, Travis L.; Moore, James B.; Su, Ji

    2014-01-01

    Airframe noise is a significant part of the overall noise of transport aircraft during the approach and landing phases of flight. Airframe noise reduction is currently emphasized under the Environmentally Responsible Aviation (ERA) and Fixed Wing (FW) Project goals of NASA. A promising concept for trailing-edge-flap noise reduction is a flexible structural element or link that connects the side edges of the deployable flap to the adjacent main-wing structure. The proposed solution is distinguished by minimization of the span-wise extent of the structural link, thereby minimizing the aerodynamic load on the link structure at the expense of increased deformation requirement. Development of such a flexible structural link necessitated application of hyperelastic materials, atypical structural configurations and novel interface hardware. The resulting highly-deformable structural concept was termed the FLEXible Side Edge Link (FLEXSEL) concept. Prediction of atypical elastomeric deformation responses from detailed structural analysis was essential for evaluating feasible concepts that met the design constraints. The focus of this paper is to describe the many challenges encountered with hyperelastic finite element modeling and the nonlinear structural analysis of evolving FLEXSEL concepts. Detailed herein is the nonlinear analysis of FLEXSEL concepts that emerged during the project which include solid-section, foamcore, hollow, extended-span and pre-stressed concepts. Coupon-level analysis performed on elastomeric interface joints, which form a part of the FLEXSEL topology development, are also presented.

  6. Evaluation of the Tone Fan Noise Design/Prediction System (TFaNS) at the NASA Glenn Research Center

    NASA Technical Reports Server (NTRS)

    Koch, L. Danielle

    1999-01-01

    Version 1.4 of TFaNS, the Tone Fan Noise Design/Prediction System. has recently been evaluated at the NASA Glenn Research Center. Data from tests of the Allison Ultra High Bypass Fan (UHBF) were used to compare to predicted farfield directivities for the radial stator configuration. There was good agreement between measured and predicted directivities at low fan speeds when rotor effects were neglected in the TFaNS calculations. At higher fan speeds, TFaNS is shown to be useful in predicting overall trends rather than absolute sound pressure levels.

  7. System Noise Assessment and the Potential for a Low Noise Hybrid Wing Body Aircraft with Open Rotor Propulsion

    NASA Technical Reports Server (NTRS)

    Thomas, Russell H.; Burley, Casey L.; Lopes, Leonard V.; Bahr, Christopher J.; Gern, Frank H.; VanZante, Dale E.

    2014-01-01

    An aircraft system noise assessment was conducted for a hybrid wing body freighter aircraft concept configured with three open rotor engines. The primary objective of the study was to determine the aircraft system level noise given the significant impact of installation effects including shielding the open rotor noise by the airframe. The aircraft was designed to carry a payload of 100,000 lbs on a 6,500 nautical mile mission. An experimental database was used to establish the propulsion airframe aeroacoustic installation effects including those from shielding by the airframe planform, interactions with the control surfaces, and additional noise reduction technologies. A second objective of the study applied the impacts of projected low noise airframe technology and a projection of advanced low noise rotors appropriate for the NASA N+2 2025 timeframe. With the projection of low noise rotors and installation effects, the aircraft system level was 26.0 EPNLdB below Stage 4 level with the engine installed at 1.0 rotor diameters upstream of the trailing edge. Moving the engine to 1.5 rotor diameters brought the system level noise to 30.8 EPNLdB below Stage 4. At these locations on the airframe, the integrated level of installation effects including shielding can be as much as 20 EPNLdB cumulative in addition to lower engine source noise from advanced low noise rotors. And finally, an additional set of technology effects were identified and the potential impact at the system level was estimated for noise only without assessing the impact on aircraft performance. If these additional effects were to be included it is estimated that the potential aircraft system noise could reach as low as 38.0 EPNLdB cumulative below Stage 4.

  8. TFaNS-Tone Fan Noise Design/Prediction System: Users' Manual TFaNS Version 1.5

    NASA Technical Reports Server (NTRS)

    Topol, David A.; Huff, Dennis L. (Technical Monitor)

    2003-01-01

    TFaNS is the Tone Fan Noise Design/Prediction System developed by Pratt & Whitney under contract to NASA Glenn. The purpose of this system is to predict tone noise emanating from a fan stage including the effects of reflection and transmission by the rotor and stator and by the duct inlet and nozzle. The first version of this design system was developed under a previous NASA contract. Several improvements have been made to TFaNS. This users' manual shows how to run this new system. TFaNS consists of the codes that compute the acoustic properties (reflection and transmission coefficients) of the various elements and writes them to files, CUP3D Fan Noise Coupling Code that reads these files, solves the coupling problem, and outputs the desired noise predictions, and AWAKEN CFD/Measured Wake Postprocessor which reformats CFD wake predictions and/or measured wake data so they can be used by the system. This report provides information on code input and file structure essential for potential users of TFaNS.

  9. Acoustic Prediction State of the Art Assessment

    NASA Technical Reports Server (NTRS)

    Dahl, Milo D.

    2007-01-01

    The acoustic assessment task for both the Subsonic Fixed Wing and the Supersonic projects under NASA s Fundamental Aeronautics Program was designed to assess the current state-of-the-art in noise prediction capability and to establish baselines for gauging future progress. The documentation of our current capabilities included quantifying the differences between predictions of noise from computer codes and measurements of noise from experimental tests. Quantifying the accuracy of both the computed and experimental results further enhanced the credibility of the assessment. This presentation gives sample results from codes representative of NASA s capabilities in aircraft noise prediction both for systems and components. These include semi-empirical, statistical, analytical, and numerical codes. System level results are shown for both aircraft and engines. Component level results are shown for a landing gear prototype, for fan broadband noise, for jet noise from a subsonic round nozzle, and for propulsion airframe aeroacoustic interactions. Additional results are shown for modeling of the acoustic behavior of duct acoustic lining and the attenuation of sound in lined ducts with flow.

  10. Advanced method and processing technology for complicated shape airframe part forming

    NASA Technical Reports Server (NTRS)

    Miodushevsky, P. V.; Rajevskaya, G. A.

    1994-01-01

    Slow deformation modes of forming give considerably higher residual fatigue life of the airframe part. It has experimentally proven that fatigue life of complicated shape integral airframe panels made of high strength aluminum alloys is significantly increased after creep deformation process. To implement the slow deformation mode forming methods, universal automated equipment was developed. Multichannel forming systems provide high accuracy of airframe part shape eliminating residual stresses and spring effect. Forming process multizone control technology was developed and experimentally proved that static/fatigue properties of formed airframe parts are increased.

  11. Measurement of Trailing Edge Noise Using Directional Array and Coherent Output Power Methods

    NASA Technical Reports Server (NTRS)

    Hutcheson, Florence V.; Brooks, Thomas F.

    2002-01-01

    The use of a directional (or phased) array of microphones for the measurement of trailing edge (TE) noise is described and tested. The capabilities of this method arc evaluated via measurements of TE noise from a NACA 63-215 airfoil model and from a cylindrical rod. This TE noise measurement approach is compared to one that is based on thc cross spectral analysis of output signals from a pair of microphones placed on opposite sides of an airframe model (COP method). Advantages and limitations of both methods arc examined. It is shown that the microphone array can accurately measures TE noise and captures its two-dimensional characteristic over a large frequency range for any TE configuration as long as noise contamination from extraneous sources is within bounds. The COP method is shown to also accurately measure TE noise but over a more limited frequency range that narrows for increased TE thickness. Finally, the applicability and generality of an airfoil self-noise prediction method was evaluated via comparison to the experimental data obtained using the COP and array measurement methods. The predicted and experimental results are shown to agree over large frequency ranges.

  12. Aircraft noise prediction program propeller analysis system IBM-PC version user's manual version 2.0

    NASA Technical Reports Server (NTRS)

    Nolan, Sandra K.

    1988-01-01

    The IBM-PC version of the Aircraft Noise Prediction Program (ANOPP) Propeller Analysis System (PAS) is a set of computational programs for predicting the aerodynamics, performance, and noise of propellers. The ANOPP-PAS is a subset of a larger version of ANOPP which can be executed on CDC or VAX computers. This manual provides a description of the IBM-PC version of the ANOPP-PAS and its prediction capabilities, and instructions on how to use the system on an IBM-XT or IBM-AT personal computer. Sections within the manual document installation, system design, ANOPP-PAS usage, data entry preprocessors, and ANOPP-PAS functional modules and procedures. Appendices to the manual include a glossary of ANOPP terms and information on error diagnostics and recovery techniques.

  13. FAA/NASA International Symposium on Advanced Structural Integrity Methods for Airframe Durability and Damage Tolerance

    NASA Technical Reports Server (NTRS)

    Harris, Charles E. (Editor)

    1994-01-01

    International technical experts in durability and damage tolerance of metallic airframe structures were assembled to present and discuss recent research findings and the development of advanced design and analysis methods, structural concepts, and advanced materials. The symposium focused on the dissemination of new knowledge and the peer-review of progress on the development of advanced methodologies. Papers were presented on: structural concepts for enhanced durability, damage tolerance, and maintainability; new metallic alloys and processing technology; fatigue crack initiation and small crack effects; fatigue crack growth models; fracture mechanics failure, criteria for ductile materials; structural mechanics methodology for residual strength and life prediction; development of flight load spectra for design and testing; and advanced approaches to resist corrosion and environmentally assisted fatigue.

  14. Ground Shake Test of the Boeing Model 360 Helicopter Airframe

    NASA Technical Reports Server (NTRS)

    Reed, D. A.; Gabel, R.

    1989-01-01

    Boeing Helicopters, together with other U.S. Helicopter manufacturers, is engaged in a finite element applications program designed to emplace in the U.S. a superior capability to utilize finite element analysis models in support of helicopter airframe structurel design. This program was given the acronym DAMVIBS (Design Analysis Methods for VIBrationS). The test plan is reviewed and results are presented for a shake test of the Boeing Model 360 helicopter. Results of the test will serve as the basis for validation of a finite element vibration model of the helicopter.

  15. Study of hypersonic propulsion/airframe integration technology

    NASA Technical Reports Server (NTRS)

    Hartill, W. R.; Goebel, T. P.; Vancamp, V. V.

    1978-01-01

    An assessment is done of current and potential ground facilities, and analysis and flight test techniques for establishing a hypersonic propulsion/airframe integration technology base. A mach 6 cruise prototype aircraft incorporating integrated Scramjet engines was considered the baseline configuration, and the assessment focused on the aerodynamic and configuration aspects of the integration technology. The study describes the key technology milestones that must be met to permit a decision on development of a prototype vehicle, and defines risk levels for these milestones. Capabilities and limitations of analysis techniques, current and potential ground test facilities, and flight test techniques are described in terms of the milestones and risk levels.

  16. IMPAC - An integrated methodology for propulsion and airframe control

    NASA Technical Reports Server (NTRS)

    Garg, Sanjay; Ouzts, Peter J.; Lorenzo, Carl F.; Mattern, Duane L.

    1991-01-01

    The NASA Lewis Research Center approach to developing integrated flight propulsion control (IFPC) technologies is an in-house research program referred to as IMPAC-Integrated Methodology for Propulsion and Airframe Control. The goals of IMPAC are to develop a viable alternative to the existing integrated control design methodologies that will allow for improved system performance and simplicity of control law synthesis and implementation, and to demonstrate the applicability of the methodology to a supersonic STOVL fighter aircraft. An overview of IMPAC is presented, including a detailed discussion of the various important design and evaluation steps in the methodology.

  17. Raspberry, not a car: context predictability and a phonological advantage in early and late learners’ processing of speech in noise

    PubMed Central

    Gor, Kira

    2014-01-01

    Second language learners perform worse than native speakers under adverse listening conditions, such as speech in noise (SPIN). No data are available on heritage language speakers’ (early naturalistic interrupted learners’) ability to perceive SPIN. The current study fills this gap and investigates the perception of Russian speech in multi-talker babble noise by the matched groups of high- and low-proficiency heritage speakers (HSs) and late second language learners of Russian who were native speakers of English. The study includes a control group of Russian native speakers. It manipulates the noise level (high and low), and context cloze probability (high and low). The results of the SPIN task are compared to the tasks testing the control of phonology, AXB discrimination and picture-word discrimination, and lexical knowledge, a word translation task, in the same participants. The increased phonological sensitivity of HSs interacted with their ability to rely on top–down processing in sentence integration, use contextual cues, and build expectancies in the high-noise/high-context condition in a bootstrapping fashion. HSs outperformed oral proficiency-matched late second language learners on SPIN task and two tests of phonological sensitivity. The outcomes of the SPIN experiment support both the early naturalistic advantage and the role of proficiency in HSs. HSs’ ability to take advantage of the high-predictability context in the high-noise condition was mitigated by their level of proficiency. Only high-proficiency HSs, but not any other non-native group, took advantage of the high-predictability context that became available with better phonological processing skills in high-noise. The study thus confirms high-proficiency (but not low-proficiency) HSs’ nativelike ability to combine bottom–up and top–down cues in processing SPIN. PMID:25566130

  18. Structure-borne low-frequency noise from multi-span bridges: A prediction method and spatial distribution

    NASA Astrophysics Data System (ADS)

    Song, X. D.; Wu, D. J.; Li, Q.; Botteldooren, D.

    2016-04-01

    Structure-borne noise from railway bridges at far-field points is an important indicator in environmental noise assessment. However, studies that predict structure-borne noise tend to model only single-span bridges, thus ignoring the sound pressure radiating from adjacent spans. To simulate the noise radiating from multi-span bridges induced by moving vehicles, the vibrations of a multi-span bridge are first obtained from a three-dimensional (3D) vehicle-track-bridge dynamic interaction simulation using the mode superposition method. A procedure based on the 2.5-dimensional (2.5D) boundary element method (BEM) is then presented to promote the efficiency of acoustical computation compared with the 3D BEM. The simulated results obtained from both the single-span and multi-span bridge models are compared with the measured results. The sound predictions calculated from the single-span model are accurate only for a minority of near-field points. In contrast, the sound pressures calculated from the multi-span bridge model match the measured results in both the time and frequency domains for all of the near-field and far-field points. The number of bridge spans required in the noise simulation is then recommended related to the distance between the track center and the field points of interest. The spatial distribution of multi-span structure-borne noise is also studied. The variation in sound pressure levels is insignificant along the length of the bridge, which validates the finding that the sound test section can be selected at an arbitrary plane perpendicular to the multi-span bridge.

  19. Hybrid de-noising approach for fiber optic gyroscopes combining improved empirical mode decomposition and forward linear prediction algorithms.

    PubMed

    Shen, Chong; Cao, Huiliang; Li, Jie; Tang, Jun; Zhang, Xiaoming; Shi, Yunbo; Yang, Wei; Liu, Jun

    2016-03-01

    A noise reduction algorithm based on an improved empirical mode decomposition (EMD) and forward linear prediction (FLP) is proposed for the fiber optic gyroscope (FOG). Referred to as the EMD-FLP algorithm, it was developed to decompose the FOG outputs into a number of intrinsic mode functions (IMFs) after which mode manipulations are performed to select noise-only IMFs, mixed IMFs, and residual IMFs. The FLP algorithm is then employed to process the mixed IMFs, from which the refined IMFs components are reconstructed to produce the final de-noising results. This hybrid approach is applied to, and verified using, both simulated signals and experimental FOG outputs. The results from the applications show that the method eliminates noise more effectively than the conventional EMD or FLP methods and decreases the standard deviations of the FOG outputs after de-noising from 0.17 to 0.026 under sweep frequency vibration and from 0.22 to 0.024 under fixed frequency vibration. PMID:27036770

  20. A three-dimensional vibroacoustic model for the prediction of underwater noise from offshore pile driving

    NASA Astrophysics Data System (ADS)

    Tsouvalas, A.; Metrikine, A. V.

    2014-04-01

    Steel monopiles are nowadays widely used as foundations for a large number of offshore structures. The installation procedure commonly involves a pile driving process which can last up to several hours depending upon pile dimensions, soil conditions and input energy of the hydraulic hammer. In impact pile driving, a hydraulic hammer delivers a series of hammer blows at the head of the pile that drive the pile into the sediment. Each hammer strike results in pile vibrations that emit strong impulsive sounds into the water column which can be harmful for the marine ecosystem. With today's increasing concern regarding the environmental impact of such operations, engineering tools which will be able to provide reliable predictions of the underwater noise levels are required. In this study, a linear semi-analytical formulation of the coupled vibroacoustics of a complete pile-water-soil interaction model is addressed. The pile is described by a high order thin shell theory whereas both water and soil are modelled as three-dimensional continua. Results obtained with the developed model indicate that the near-field response in the water column consists mainly of pressure conical waves generated by the supersonic compressional waves in the pile excited by the impact hammer. The soil response is dominated by shear waves with almost vertical polarization. The Scholte waves are also generated at the water-seabed interface which can produce pressure fluctuations in the water column that are particularly significant close to the sea floor. The effects of soil elasticity and pile size are thoroughly investigated and their influence on the generated pressure levels is highlighted. The results are also compared with those ones of a similar model in which the soil is treated as an equivalent acoustic fluid. It is shown that the latter approximation can yield inaccurate results at low frequencies especially for harder soil sediments.

  1. A structured population modeling framework for quantifying and predicting gene expression noise in flow cytometry data.

    PubMed

    Flores, Kevin B

    2013-07-01

    We formulated a structured population model with distributed parameters to identify mechanisms that contribute to gene expression noise in time-dependent flow cytometry data. The model was validated using cell population-level gene expression data from two experiments with synthetically engineered eukaryotic cells. Our model captures the qualitative noise features of both experiments and accurately fit the data from the first experiment. Our results suggest that cellular switching between high and low expression states and transcriptional re-initiation are important factors needed to accurately describe gene expression noise with a structured population model.

  2. Prediction and analysis of infra and low-frequency noise of upwind horizontal axis wind turbine using statistical wind speed model

    SciTech Connect

    Lee, Gwang-Se; Cheong, Cheolung

    2014-12-15

    Despite increasing concern about low-frequency noise of modern large horizontal-axis wind turbines (HAWTs), few studies have focused on its origin or its prediction methods. In this paper, infra- and low-frequency (the ILF) wind turbine noise are closely examined and an efficient method is developed for its prediction. Although most previous studies have assumed that the ILF noise consists primarily of blade passing frequency (BPF) noise components, these tonal noise components are seldom identified in the measured noise spectrum, except for the case of downwind wind turbines. In reality, since modern HAWTs are very large, during rotation, a single blade of the turbine experiences inflow with variation in wind speed in time as well as in space, breaking periodic perturbations of the BPF. Consequently, this transforms acoustic contributions at the BPF harmonics into broadband noise components. In this study, the ILF noise of wind turbines is predicted by combining Lowson’s acoustic analogy with the stochastic wind model, which is employed to reproduce realistic wind speed conditions. In order to predict the effects of these wind conditions on pressure variation on the blade surface, unsteadiness in the incident wind speed is incorporated into the XFOIL code by varying incident flow velocities on each blade section, which depend on the azimuthal locations of the rotating blade. The calculated surface pressure distribution is subsequently used to predict acoustic pressure at an observing location by using Lowson’s analogy. These predictions are compared with measured data, which ensures that the present method can reproduce the broadband characteristics of the measured low-frequency noise spectrum. Further investigations are carried out to characterize the IFL noise in terms of pressure loading on blade surface, narrow-band noise spectrum and noise maps around the turbine.

  3. Prediction and analysis of infra and low-frequency noise of upwind horizontal axis wind turbine using statistical wind speed model

    NASA Astrophysics Data System (ADS)

    Lee, Gwang-Se; Cheong, Cheolung

    2014-12-01

    Despite increasing concern about low-frequency noise of modern large horizontal-axis wind turbines (HAWTs), few studies have focused on its origin or its prediction methods. In this paper, infra- and low-frequency (the ILF) wind turbine noise are closely examined and an efficient method is developed for its prediction. Although most previous studies have assumed that the ILF noise consists primarily of blade passing frequency (BPF) noise components, these tonal noise components are seldom identified in the measured noise spectrum, except for the case of downwind wind turbines. In reality, since modern HAWTs are very large, during rotation, a single blade of the turbine experiences inflow with variation in wind speed in time as well as in space, breaking periodic perturbations of the BPF. Consequently, this transforms acoustic contributions at the BPF harmonics into broadband noise components. In this study, the ILF noise of wind turbines is predicted by combining Lowson's acoustic analogy with the stochastic wind model, which is employed to reproduce realistic wind speed conditions. In order to predict the effects of these wind conditions on pressure variation on the blade surface, unsteadiness in the incident wind speed is incorporated into the XFOIL code by varying incident flow velocities on each blade section, which depend on the azimuthal locations of the rotating blade. The calculated surface pressure distribution is subsequently used to predict acoustic pressure at an observing location by using Lowson's analogy. These predictions are compared with measured data, which ensures that the present method can reproduce the broadband characteristics of the measured low-frequency noise spectrum. Further investigations are carried out to characterize the IFL noise in terms of pressure loading on blade surface, narrow-band noise spectrum and noise maps around the turbine.

  4. Noise produced by turbulent flow into a rotor: Theory manual for atmospheric turbulence prediction and mean flow and turbulence contraction prediction

    NASA Technical Reports Server (NTRS)

    Simonich, J. C.

    1989-01-01

    Prediction of helicopter main rotor noise due to ingestion of atmospheric turbulence was analyzed. The analysis combines several different models that describe the fluid mechanics of the turbulence and the ingestion process. Two models, atmospheric turbulence, and mean flow and turbulence contraction were covered. The third model, covered in a separate report, describes the rotor acoustic mode. The method incorporates the atmospheric turbulence model and a rapid distortion turbulence contraction description to determine the statistics of the anisotropic turbulence at the rotor plane. The analytical basis for a module was provided which was incorporated in NASA's ROTONET helicopter noise prediction program. The mean flow and turbulence statistics associated with the atmospheric boundary layer were modeled including effects of atmospheric stability length, wind speed, and altitude. The turbulence distortion process is modeled as a deformation of vortex filaments (which represent the turbulence field) by a mean flow field due to the rotor inflow.

  5. Thermal imager fixed pattern noise prediction using a characterization of the infrared detector

    NASA Astrophysics Data System (ADS)

    Mariani, Paolo; Zatti, Stefano; Giunti, Claudio; Sozzi, Barbara; Guadagnoli, Emanuele; Porta, Antonio

    2014-12-01

    Cooled infrared detectors are typically characterized by well-known electro-optical parameters: responsivity, noise equivalent temperature difference, shot noise, 1/f noise, and so on. Particularly important for staring arrays is also the residual fixed pattern noise (FPN) that can be obtained after the application of the nonuniformity correction (NUC) algorithm. A direct measure of this parameter is usually hard to define because the residual FPN strongly depends, other than on the detector, on the choice of the NUC algorithm and the operative scenario. We introduce three measurable parameters: instability, nonlinearity, and a residual after a polynomial fitting of the detector response curve, and we demonstrate how they are related to the residual FPN after the application of an NUC (the relationship with three common correction algorithms is discussed). A comparison with experimental data is also presented and discussed.

  6. Insights into Airframe Aerodynamics and Rotor-on-Wing Interactions from a 0.25-Scale Tiltrotor Wind Tunnel Model

    NASA Technical Reports Server (NTRS)

    Young, L. A.; Lillie, D.; McCluer, M.; Yamauchi, G. K.; Derby, M. R.

    2001-01-01

    A recent experimental investigation into tiltrotor aerodynamics and acoustics has resulted in the acquisition of a set of data related to tiltrotor airframe aerodynamics and rotor and wing interactional aerodynamics. This work was conducted in the National Full-scale Aerodynamics Complex's (NFAC) 40-by-80 Foot Wind Tunnel, at NASA Ames Research Center, on the Full-Span Tilt Rotor Aeroacoustic Model (TRAM). The full-span TRAM wind tunnel test stand is nominally based on a quarter-scale representation of the V-22 aircraft. The data acquired will enable the refinement of analytical tools for the prediction of tiltrotor aeromechanics and aeroacoustics.

  7. Investigation on the use of optimization techniques for helicopter airframe vibrations design studies

    NASA Technical Reports Server (NTRS)

    Sreekanta Murthy, T.

    1992-01-01

    Results of the investigation of formal nonlinear programming-based numerical optimization techniques of helicopter airframe vibration reduction are summarized. The objective and constraint function and the sensitivity expressions used in the formulation of airframe vibration optimization problems are presented and discussed. Implementation of a new computational procedure based on MSC/NASTRAN and CONMIN in a computer program system called DYNOPT for optimizing airframes subject to strength, frequency, dynamic response, and dynamic stress constraints is described. An optimization methodology is proposed which is thought to provide a new way of applying formal optimization techniques during the various phases of the airframe design process. Numerical results obtained from the application of the DYNOPT optimization code to a helicopter airframe are discussed.

  8. Predicting stochastic systems by noise sampling, and application to the El Niño-Southern Oscillation.

    PubMed

    Chekroun, Mickaël David; Kondrashov, Dmitri; Ghil, Michael

    2011-07-19

    Interannual and interdecadal prediction are major challenges of climate dynamics. In this article we develop a prediction method for climate processes that exhibit low-frequency variability (LFV). The method constructs a nonlinear stochastic model from past observations and estimates a path of the "weather" noise that drives this model over previous finite-time windows. The method has two steps: (i) select noise samples--or "snippets"--from the past noise, which have forced the system during short-time intervals that resemble the LFV phase just preceding the currently observed state; and (ii) use these snippets to drive the system from the current state into the future. The method is placed in the framework of pathwise linear-response theory and is then applied to an El Niño-Southern Oscillation (ENSO) model derived by the empirical model reduction (EMR) methodology; this nonlinear model has 40 coupled, slow, and fast variables. The domain of validity of this forecasting procedure depends on the nature of the system's pathwise response; it is shown numerically that the ENSO model's response is linear on interannual time scales. As a result, the method's skill at a 6- to 16-month lead is highly competitive when compared with currently used dynamic and statistic prediction methods for the Niño-3 index and the global sea surface temperature field. PMID:21730171

  9. Influences of word predictability and type of masker noise on intelligibility of sung text in live concerts.

    PubMed

    Heinrich, Antje; Knight, Sarah; Hawkins, Sarah

    2015-10-01

    Vocal music is often intended to convey meaning, but how effectively this is achieved is poorly understood. This study systematically assessed the influence of three non-phonetic factors on the intelligibility of sung words in six public concerts in different venues: word predictability from sentence context, type of masker noise (spoken babble, sung vowels, [∫(w)]), and signal-to-noise ratio (SNR). Stimuli were sung live by a professional a cappella ensemble with one male singing target sentences and five others (two female) producing the masker sounds. The concert audiences (N = 319) reported the final word of each sentence using a handheld voting device, from four phonetically- and semantically-controlled written alternatives projected onto a screen after the sentence was sung. Although overall accuracy differed between performances, intelligibility patterns were robust across concerts. They included predicted main effects of masker noise type ([∫(w)] masking least disruptive, babble most), SNR (high > low), semantic predictability (high > low), listener age (young > old), and listener language status (native > non-native), and some strong interactions. These results suggest that, despite acoustic differences between sung and spoken words and the unusual and varied experimental venues, key findings from traditional speech research apply to sung words, given appropriate musical composition. PMID:26520319

  10. Prediction of Turbulence-Generated Noise in Unheated Jets. Part 1; JeNo Technical Manual (Version 1.0)

    NASA Technical Reports Server (NTRS)

    Khavaran, Abbas; Bridges, James; Georgiadis, Nicholas

    2005-01-01

    The model-based approach, used by the JeNo code to predict jet noise spectral directivity, is described. A linearized form of Lilley's equation governs the non-causal Green s function of interest, with the non-linear terms on the right hand side identified as the source. A Reynolds-averaged Navier-Stokes (RANS) solution yields the required mean flow for the solution of the propagation Green s function in a locally parallel flow. The RANS solution also produces time- and length-scales needed to model the non-compact source, the turbulent velocity correlation tensor, with exponential temporal and spatial functions. It is shown that while an exact non-causal Green s function accurately predicts the observed shift in the location of the spectrum peak with angle as well as the angularity of sound at low to moderate Mach numbers, the polar directivity of radiated sound is not entirely captured by this Green s function at high subsonic and supersonic acoustic Mach numbers. Results presented for unheated jets in the Mach number range of 0.51 to 1.8 suggest that near the peak radiation angle of high-speed jets, a different source/Green s function convolution integral may be required in order to capture the peak observed directivity of jet noise. A sample Mach 0.90 heated jet is also discussed that highlights the requirements for a comprehensive jet noise prediction model.

  11. Aircraft noise-induced awakenings are more reasonably predicted from relative than from absolute sound exposure levels.

    PubMed

    Fidell, Sanford; Tabachnick, Barbara; Mestre, Vincent; Fidell, Linda

    2013-11-01

    Assessment of aircraft noise-induced sleep disturbance is problematic for several reasons. Current assessment methods are based on sparse evidence and limited understandings; predictions of awakening prevalence rates based on indoor absolute sound exposure levels (SELs) fail to account for appreciable amounts of variance in dosage-response relationships and are not freely generalizable from airport to airport; and predicted awakening rates do not differ significantly from zero over a wide range of SELs. Even in conjunction with additional predictors, such as time of night and assumed individual differences in "sensitivity to awakening," nominally SEL-based predictions of awakening rates remain of limited utility and are easily misapplied and misinterpreted. Probabilities of awakening are more closely related to SELs scaled in units of standard deviates of local distributions of aircraft SELs, than to absolute sound levels. Self-selection of residential populations for tolerance of nighttime noise and habituation to airport noise environments offer more parsimonious and useful explanations for differences in awakening rates at disparate airports than assumed individual differences in sensitivity to awakening.

  12. Influences of word predictability and type of masker noise on intelligibility of sung text in live concerts.

    PubMed

    Heinrich, Antje; Knight, Sarah; Hawkins, Sarah

    2015-10-01

    Vocal music is often intended to convey meaning, but how effectively this is achieved is poorly understood. This study systematically assessed the influence of three non-phonetic factors on the intelligibility of sung words in six public concerts in different venues: word predictability from sentence context, type of masker noise (spoken babble, sung vowels, [∫(w)]), and signal-to-noise ratio (SNR). Stimuli were sung live by a professional a cappella ensemble with one male singing target sentences and five others (two female) producing the masker sounds. The concert audiences (N = 319) reported the final word of each sentence using a handheld voting device, from four phonetically- and semantically-controlled written alternatives projected onto a screen after the sentence was sung. Although overall accuracy differed between performances, intelligibility patterns were robust across concerts. They included predicted main effects of masker noise type ([∫(w)] masking least disruptive, babble most), SNR (high > low), semantic predictability (high > low), listener age (young > old), and listener language status (native > non-native), and some strong interactions. These results suggest that, despite acoustic differences between sung and spoken words and the unusual and varied experimental venues, key findings from traditional speech research apply to sung words, given appropriate musical composition.

  13. State of the Art in Beta Titanium Alloys for Airframe Applications

    NASA Astrophysics Data System (ADS)

    Cotton, James D.; Briggs, Robert D.; Boyer, Rodney R.; Tamirisakandala, Sesh; Russo, Patrick; Shchetnikov, Nikolay; Fanning, John C.

    2015-06-01

    Beta titanium alloys were recognized as a distinct materials class in the 1950s, and following the introduction of Ti-13V-11Cr-3Al in the early 1960s, intensive research occurred for decades thereafter. By the 1980s, dozens of compositions had been explored and sufficient work had been accomplished to warrant the first major conference in 1983. Metallurgists of the time recognized beta alloys as highly versatile and capable of remarkable property development at much lower component weights than steels, coupled with excellent corrosion resistance. Although alloys such as Ti-15V-3Al-3Sn-3Cr, Ti-10V-2Fe-3Al and Ti-3AI-8V-6Cr-4Mo-4Zr (Beta C) were commercialized into well-known airframe systems by the 1980s, Ti-13V-11Cr-3Al was largely discarded following extensive employment on the SR-71 Blackbird. The 1990s saw the implementation of specialty beta alloys such as Beta 21S and Alloy C, in large part for their chemical and oxidation resistance. It was also predicted that by the 1990s, cost would be the major limitation on expansion into new applications. This turned out to be true and is part of the reason for some stagnation in commercialization of new such compositions over the past two decades, despite a good understanding of the relationships among chemistry, processing, and performance and some very attractive offerings. Since then, only a single additional metastable beta alloy, Ti-5Al-5V-5Mo-3Cr-0.5Fe, has been commercialized in aerospace, although low volumes of other chemistries have found a place in the biomedical implant market. This article examines the evolution of this important class of materials and the current status in airframe applications. It speculates on challenges for expanding their use.

  14. Time-domain inflow boundary condition for turbulence-airfoil interaction noise prediction using synthetic turbulence modeling

    NASA Astrophysics Data System (ADS)

    Kim, Daehwan; Heo, Seung; Cheong, Cheolung

    2015-03-01

    The present paper deals with development of the synthetic turbulence inflow boundary condition (STIBC) to predict inflow broadband noise generated by interaction between turbulence and an airfoil/a cascade of airfoils in the time-domain. The STIBC is derived by combining inflow boundary conditions that have been successfully applied in external and internal computational aeroacoustics (CAA) simulations with a synthetic turbulence model. The random particle mesh (RPM) method based on a digital filter is used as the synthetic turbulence model. Gaussian and Liepmann spectra are used to define the filters for turbulence energy spectra. The linearized Euler equations are used as governing equations to evaluate the suitability of the STIBC in time-domain CAA simulations. First, the velocity correlations and energy spectra of the synthesized turbulent velocities are compared with analytic ones. The comparison results reveal that the STIBC can reproduce a turbulent velocity field satisfying the required statistical characteristics of turbulence. Particularly, the Liepmann filter representing a non-Gaussian filter is shown to be effectively described by superposing the Gaussian filters. Each Gaussian filter has a different turbulent kinetic energy and integral length scale. Second, two inflow noise problems are numerically solved using the STIBC: the turbulence-airfoil interaction and the turbulence-a cascade of airfoils interaction problems. The power spectrum of noise due to an isolated flat plate airfoil interacting with incident turbulence is predicted, and its result is successfully validated against Amiet's analytic model (Amiet, 1975) [4]. The prediction results of the upstream and downstream acoustic power spectra from a cascade of flat plates are then compared with Cheong's analytic model (Cheong et al., 2006) [30]. These comparisons are also in excellent agreement. On the basis of these illustrative computation results, the STIBC is expected to be applied to

  15. Unsteady Fast Random Particle Mesh method for efficient prediction of tonal and broadband noises of a centrifugal fan unit

    NASA Astrophysics Data System (ADS)

    Heo, Seung; Cheong, Cheolung; Kim, Taehoon

    2015-09-01

    In this study, efficient numerical method is proposed for predicting tonal and broadband noises of a centrifugal fan unit. The proposed method is based on Hybrid Computational Aero-Acoustic (H-CAA) techniques combined with Unsteady Fast Random Particle Mesh (U-FRPM) method. The U-FRPM method is developed by extending the FRPM method proposed by Ewert et al. and is utilized to synthesize turbulence flow field from unsteady RANS solutions. The H-CAA technique combined with U-FRPM method is applied to predict broadband as well as tonal noises of a centrifugal fan unit in a household refrigerator. Firstly, unsteady flow field driven by a rotating fan is computed by solving the RANS equations with Computational Fluid Dynamic (CFD) techniques. Main source regions around the rotating fan are identified by examining the computed flow fields. Then, turbulence flow fields in the main source regions are synthesized by applying the U-FRPM method. The acoustic analogy is applied to model acoustic sources in the main source regions. Finally, the centrifugal fan noise is predicted by feeding the modeled acoustic sources into an acoustic solver based on the Boundary Element Method (BEM). The sound spectral levels predicted using the current numerical method show good agreements with the measured spectra at the Blade Pass Frequencies (BPFs) as well as in the high frequency range. On the more, the present method enables quantitative assessment of relative contributions of identified source regions to the sound field by comparing predicted sound pressure spectrum due to modeled sources.

  16. The NASA/industry Design Analysis Methods for Vibrations (DAMVIBS) program: Boeing Helicopters airframe finite element modeling

    NASA Technical Reports Server (NTRS)

    Gabel, R.; Lang, P.; Reed, D.

    1993-01-01

    Mathematical models based on the finite element method of structural analysis, as embodied in the NASTRAN computer code, are routinely used by the helicopter industry to calculate airframe static internal loads used for sizing structural members. Historically, less reliance has been placed on the vibration predictions based on these models. Beginning in the early 1980's NASA's Langley Research Center initiated an industry wide program with the objective of engendering the needed trust in vibration predictions using these models and establishing a body of modeling guides which would enable confident future prediction of airframe vibration as part of the regular design process. Emphasis in this paper is placed on the successful modeling of the Army/Boeing CH-47D which showed reasonable correlation with test data. A principal finding indicates that improved dynamic analysis requires greater attention to detail and perhaps a finer mesh, especially the mass distribution, than the usual stress model. Post program modeling efforts show improved correlation placing key modal frequencies in the b/rev range with 4 percent of the test frequencies.

  17. An Integrated Low-Speed Performance and Noise Prediction Methodology for Subsonic Aircraft

    NASA Technical Reports Server (NTRS)

    Olson, E. D.; Mavris, D. N.

    2000-01-01

    An integrated methodology has been assembled to compute the engine performance, takeoff and landing trajectories, and community noise levels for a subsonic commercial aircraft. Where feasible, physics-based noise analysis methods have been used to make the results more applicable to newer, revolutionary designs and to allow for a more direct evaluation of new technologies. The methodology is intended to be used with approximation methods and risk analysis techniques to allow for the analysis of a greater number of variable combinations while retaining the advantages of physics-based analysis. Details of the methodology are described and limited results are presented for a representative subsonic commercial aircraft.

  18. Open Rotor Noise Shielding by Blended-Wing-Body Aircraft

    NASA Technical Reports Server (NTRS)

    Guo, Yueping; Czech, Michael J.; Thomas, Russell H.

    2015-01-01

    This paper presents an analysis of open rotor noise shielding by Blended Wing Body (BWB) aircraft by using model scale test data acquired in the Boeing Low Speed Aeroacoustic Facility (LSAF) with a legacy F7/A7 rotor model and a simplified BWB platform. The objective of the analysis is the understanding of the shielding features of the BWB and the method of application of the shielding data for noise studies of BWB aircraft with open rotor propulsion. By studying the directivity patterns of individual tones, it is shown that though the tonal energy distribution and the spectral content of the wind tunnel test model, and thus its total noise, may differ from those of more advanced rotor designs, the individual tones follow directivity patterns that characterize far field radiations of modern open rotors, ensuring the validity of the use of this shielding data. Thus, open rotor tonal noise shielding should be categorized into front rotor tones, aft rotor tones and interaction tones, not only because of the different directivities of the three groups of tones, but also due to the differences in their source locations and coherence features, which make the respective shielding characteristics of the three groups of tones distinctly different from each other. To reveal the parametric trends of the BWB shielding effects, results are presented with variations in frequency, far field emission angle, rotor operational condition, engine installation geometry, and local airframe features. These results prepare the way for the development of parametric models for the shielding effects in prediction tools.

  19. Bibliography on propulsion airframe integration technologies for high-speed civil transport applications, 1980-1991

    NASA Technical Reports Server (NTRS)

    Anderson, David J.; Mizukami, Masashi

    1993-01-01

    NASA has initiated the High Speed Research (HSR) program with the goal to develop technologies for a new generation, economically viable, environmentally acceptable, supersonic transport (SST) called the High Speed Civil Transport (HSCT). A significant part of this effort is expected to be in multidisciplinary systems integration, such as in propulsion airframe integration (PAI). In order to assimilate the knowledge database on PAI for SST type aircraft, a bibliography on this subject was compiled. The bibliography with over 1200 entries, full abstracts, and indexes. Related topics are also covered, such as the following: engine inlets, engine cycles, nozzles, existing supersonic cruise aircraft, noise issues, computational fluid dynamics, aerodynamics, and external interference. All identified documents from 1980 through early 1991 are included; this covers the latter part of the NASA Supersonic Cruise Research (SCR) program and the beginnings of the HSR program. In addition, some pre-1980 documents of significant merit or reference value are also included. The references were retrieved via a computerized literature search using the NASA RECON database system.

  20. Rotor noise

    NASA Astrophysics Data System (ADS)

    Schmitz, F. H.

    1991-08-01

    The physical characteristics and sources of rotorcraft noise as they exist today are presented. Emphasis is on helicopter-like vehicles, that is, on rotorcraft in nonaxial flight. The mechanisms of rotor noise are reviewed in a simple physical manner for the most dominant sources of rotorcraft noise. With simple models, the characteristic time- and frequency-domain features of these noise sources are presented for idealized cases. Full-scale data on several rotorcraft are then reviewed to allow for the easy identification of the type and extent of the radiating noise. Methods and limitations of using scaled models to test for several noise sources are subsequently presented. Theoretical prediction methods are then discussed and compared with experimental data taken under very controlled conditions. Finally, some promising noise reduction technology is reviewed.