Airframe Noise Prediction Research Articles

Proposing Method for Airframe Noise Prediction Benefitting Indonesian Aircraft Design

Proposing Method for Airframe Noise Prediction Benefitting Indonesian Aircraft Design

Airframe noise modeling and prediction

With the installation on the most recent aircraft of large engines with a bypass ratio of 10–12, the engine noise contribution to the overall aircraft noise was reduced, and airframe noise has now become one of the most important noise sources during the approach phase. The paper presents a review of airframe noise analytical modeling and prediction. Indeed, aircraft manufacturers need prediction tools for rapid assessment of noise exposure around airports, standards certification noise levels as defined by the International Civil Aviation Organisation and optimized operational procedures at various stage of aircraft design. At present, this kind of noise model can only be based on analytical or semi-empirical modeling. For both slats, flaps and landing gears, main noise mechanisms are presented, as well as the associated noise models used at Airbus for airframe noise prediction. These models were validated with specific noise flight tests on various Airbus aircraft dedicated specifically to airframe noise measurements. Validation cases are presented at the end of the paper for three examples.

Toward Noise Certification during Design: Airframe Noise Simulations for Full-Scale, Complete Aircraft.

An overview of a recent, NASA-sponsored effort to substantially advance simulation-based airframe noise prediction is presented. An accurate characterization of this component of aircraft noise requires a high-fidelity representation of the finer geometrical details associated with the landing gear and wing high-lift devices, such as slats and flaps, which constitute major noise sources. To achieve this ambitious goal, a systematic approach was followed to extend our current state-of-the-art computational tools to a full-scale, complete aircraft in landing configuration within a realistic flight environment. The work involved several phases: high-fidelity, large-scale, unsteady flow simulations; model-scale experiments in ground-based facilities; and farfield noise prediction for a full-scale, complete aircraft. The comprehensive aeroacoustic database generated during the course of the effort provided a wealth of relevant information for full validation and benchmarking of the advanced computational tools used in the present work. The database will also foster the development of simulation methodologies with improved predictive capabilities.

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

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.

Framework for a Landing-Gear Model and Acoustic Prediction

numbers. The initial landing-gear-model-and-acoustic-prediction predictions for dressed configurations show an increase in noise in the frequency range representative of the added landing-gear components. The landing-gear model and acoustic prediction is also compared with wind-tunnel measurements for much larger landing-gear geometry,measuredintheVirginiaPolytechnicInstituteandStateUniversityacousticwindtunnel.Predictionsshow the ability of the landing-gear model and acoustic prediction to predict the contribution of each component to the overall values. Although the landing-gear model and acoustic prediction is in an early stage of development, the present agreement between the calculations and measurements suggests the method has promise for future application in the prediction of airframe noise.

Airframe noise prediction

This presentation discusses the prediction of aircraft airframe noise, namely, the noise that is generated by non‐propulsion components of aircraft, including the leaning edge slats, the side edges of flaps and the landing gears. An overview will be given on various methodologies, ranging from empirical prediction to more physics‐based modeling to full‐blown numerical simulation. The advantages of each method will be discussed and compared with each other to reveal the most suitable application domain of each method. Detailed discussions will be given to the physics‐based modeling, such as the acoustic analogy, which is ranked in between empirical and numerical methods in various aspects, including accuracy, turn‐around time, limitations on geometry and flow conditions, and applicability/ feasibility in practical design applications. Examples will be given to demonstrate the applications of acoustic analogy in both noise prediction and noise reduction treatment design. Critical elements of the method that can and need to be improved to further mature the method will also be identified and discussed, providing potential directions for future research and development.

Overview of revolutionary aircraft for quiet communities workshop

At some time in the future, technical advances, environmental imperatives, societal expectations for mobility, and economic drivers will dictate that radically different aircraft will be built and flown. Therefore, aircraft designs will change even if low noise were not one of the environmental imperatives, and acousticians must be aware of the possible directions for aircraft design and the resulting opportunities and challenges for noise control. To address this need, the National Aeronautics and Space Administration sponsored a workshop entitled Revolutionary Aircraft for Quiet Communities in Hampton, VA, 24‐26 July 2007. Twenty‐six talks covered aircraft design, interior noise challenges, airframe noise, propulsion, and aircraft noise prediction. Revolutionary aircraft will employ dramatically improved materials, propulsion systems, and flow control technology to improve efficiency and enhance mobility. Five hours of discussion surfaced many concerns and recommendations, including the increasing need ...

Research at DLR towards airframe noise prediction and reduction

Abstract In the final approach phase airframe noise represents the ultimate aircraft noise barrier for future aircraft when equipped with quiet UHBR engines. This paper summarizes the results achieved at DLR in the development of methods and tools for airframe noise prediction and reduction. Numerous DLR internal, national and EC co-financed research projects were conducted to investigate the aerodynamic noise of wing high-lift devices and landing gears, which constitute the major airframe noise contributors. Experimental noise source studies where performed on both scaled 2D generic and complete high-lift wing models and on an A320 full-scale wing section as well as on full-scale landing gears. These tests aimed at the quantification of airframe noise levels, the identification of major aeroacoustic sources and the development of noise prediction schemes. The results from these experiments provided information on the noise generation mechanisms and radiation characteristics from slats and landing gears. Devices were developed, which promise an overall airframe noise reduction potential of up to 5 dB, relative to airframe noise levels of current aircraft. While such technologies already reach a high “technology readiness level” for landing gears, the development of noise reduction means for high-lift devices still remains in a research stage. For the development of low-noise high-lift devices for future aircraft by means of computational aeroacoustics, low-cost simulation codes were developed, validated and applied to a variety of 2D airframe noise problems.

Development of Computational Aeroacoustics Tools for Airframe Noise Calculations

This paper discusses the development of computational aeroacoustics (CAA) tools for airframe noise analysis and prediction. We review recent progress in this topic, but emphasize our vision for the future development of such tools. Our intention is for this vision to drive future CAA research in directions that will accelerate widespread use of CAA for airframe noise applications. We discuss the needs for accuracy, efficiency, and easy interface with other design tools and illustrate how CAA tools may help future aircraft design. We explain what appears to be achievable in a 20-year time frame, and what goals will probably take longer. Important barrier issues include the effects of numerical dispersion and dissipation, the treatment of highly curved, irregular boundary surfaces, and grid generation. Beyond these largely numerical issues, we discuss the role of physics-based modeling, including turbulence modeling in unsteady flow computations and the importance of developing sophisticated techniques for analyzing results of computations. Numerical simulations combined with the acoustic analogy methodology to predict noise are also reviewed. Finally, we discuss how to use recent advances in measurement techniques for CAA tool validation, which is an integral part of future development.

THE PREDICTION OF AIRFRAME NOISE AND COMPARISON WITH EXPERIMENT

The success of the high bypass ratio turbofan engine in reducing the external noise of civil transport aircraft at take-off and landing, while improving the economics of air travel, has opened up the debate as to how much further it will be possible to reduce aircraft noise by the introduction of new aircraft or existing aircraft retrofitted with new engines. Irrespective of what new technology can offer in respect of further engine noise reduction for no loss of performance, it is now clear that all future aircraft will require airframe noise to be reduced on the approach, since today it is comparable with engine noise. This paper discusses the major components of airframe noise and reviews the present state of airframe noise prediction. Finally, a comparison is made between prediction and experimental data and the prospects for airframe noise reduction.

Assessment of airframe noise

A component method of airframe noise prediction is used to predict levels of operational and proposed aircraft airframe noise to assess the contribution of airframe noise to community noise levels. This is done after first evaluating the prediction method using newly acquired detailed measurements from full-scale aircraft and models. In the course of the evaluation, modeling techniques of airframe noise sources are examined with attention to scaling. Finally, when used to predict approach airframe EPNLs, the levels fell about 10 EPNdB below current noise regulations and about 5 EPNdB below proposed noise regulations.

Noise Component Method for Airframe Noise

A method was developed for predicting aerodynamic noise radiated by an airframe. Separate contributions are calculated for the clean wing, horizontal tail, vertical tail, landing gear, leading-edge slats and flaps, and trailing-edge flaps. Each noise component is predicted using scaling laws appropriate to that component, with amplitudes matched to available data. Spectra calculated by this method, the NASA Aircraft Noise Prediction Program (ANOPP) total aircraft method, and the drag element method are compared with flyover noise data for a twin-propeller lightplane, a business jet, and a jumbo jet. from high bypass ratio turbofans with extensive inlet and exhaust acoustic suppression, at approach power setting. Future certification levels must be based on what can be achieved with economically viable airframes and propulsion systems. Thus it is necessary to understand the fundamental processes of airframe noise radiation. Several methods for predicting airframe noise were examined by NASA as part of the Aircraft Noise Prediction Program (ANOPP). Two airframe noise prediction methods, the total aircraft method for aircraft in the clean con- figuration, and the drag element method for all con- figurations, were recommended2 and were subsequently programmed by NASA Aircraft Noise Prediction Office. Verification by comparisons with measured airframe noise spectra have not been published for the total aircraft method and were available for only a few cases for the drag element method. More recently, a noise component method was developed for the Federal Aviation Administration under Contract DOT-FA76WA-3821.3 The purposes of this paper are to describe that method, including recent revisions, and to evaluate the validity of these several airframe noise prediction methods by comparisons between calculated and measured flyover noise spectra. NASA ANOPP Methods Two NASA ANOPP methods for calculating airframe noise were obtained from NASA within one computer program. Option 1 of that computer program is the total aircraft noise method developed by Hardin 2 for clean air- frames. It was derived from a regression analysis of measured peak OASPL for selected aircraft flyovers. These OASPL's

Approximate Prediction of Airframe Noise

Theme IRFRAME noise from aerodynamically clean airframes A is assumed to be trailing-edge noise caused by convection of the wing turbulent boundary layer past the wing trailing edge. Resulting maximum flyover noise is predicted from an existing solution for trailing-edge noise plus estimates of turbulent boundary-layer integral scale length and turbulence intensity. Typical airplanes with retracted or well-faired landing gear but with wing-mounted engine nacelles and extensive trailing-edge flap-track shields generate about 8 dB more than this minimum trailing-edge noise. Resulting predicted acoustic intensity varies with airspeed t o the fifth power, in agreement with a linear regression analysis of flight data. ' Trailing-edge noise has been previously inferred' to be the mechanism for airframe noise because of the observed fifthpower velocity dependence. In contrast, other analyses 3.4 have assumed a lift dipole directivity associated with fluctuating-drag noise mechanisms and have predicted a sixthpower velocity dependence.