Effect of flight path dispersion on airport noise

The social impact of aircraft noise is usually assessed by way of estimates of the “energy sum” of noise delivered to points on the ground. Though in such estimates one commonly supposes that the noise generating aircraft fly along specific trajectories, it has been shown that statistical dispersion about the mean flight path can be significant. The literature suggests that the effect is dominated by lateral excursions due to fluctuations in heading during departure.In this paper an additive term is presented to correct “energy sum” based noise indices for lateral flight path dispersion. Gaussian distribution of flight paths and logarithmic decay of noise level are assumed in the mathematical model. Under these conditions, the correction term depends only on the horizontal and vertical distances between the observer and the closest point on the mean flight path, both distances being normalized by the standard deviation of the lateral fluctuations.The limited data that have been reported indicate that the standard deviation tends to grow linearly with distance after liftoff. If so, the correction for a given aircraft category will tend to be constant along lines radiating outward from the lift-off point. Lateral dispersion always reduces the noise index along the ground track. This reduction decreases to either side, vanishing at some 3 to 6 degrees azimuth. For larger azimuth angles, dispersion increases noise energy-the maximum occurring at some 10 degrees. In typical airport situations this maximum increase may be as great as four decibels. Accordingly, as these results represent a lower bound for them, dispersive effects may significantly influence airport exposure.A numerical example illustrates how lateral flight path dispersion broadens and foreshortens contours of equal noise exposure.     

基于粒子群的高超声速飞行器闭环制导研究

对于高超声速飞行器的研究来说,凭借其超高的飞行速度和飞行高度,能够在短时间内飞行更远的距离。为了达到作战要求,需要规划整个飞行轨迹,而最为重要的便是上升段的制导问题。本文以X-33高超声速飞行器模型为研究对象,提出基于粒子群算法的闭环制导策略,实时修正飞行轨迹,使飞行器最终准确到达目标位置;并对该方法的可靠性进行了仿真验证。仿真结果表明,基于粒子群算法的闭环制导策略优化精度高,物理概念明确,能满足高超声速飞行器上升段的闭环制导需求。     

基于散射矩阵法的飞机壁板声学优化设计

采用散射矩阵法分析夹层板结构声学特性,并对典型的夹层板结构即飞机壁板进行声学优化,预计飞机壁板隔声特性,获得蒙皮、隔声隔热层、内饰板及它们的组合结构的声学性能。针对尾吊飞机客舱后部噪声过大问题,通过增加铺设隔热隔声层以及部分区域优化安装阻尼层等一系列被动降噪处理方法,对主要传递路径的飞机壁板结构进行优化,降低客舱后部噪声水平,并进行试验验证。试验结果表明:散射矩阵法可快速准确获得夹层结构的隔声性能,并与混响室法测试结果吻合较好;在厚度不变的前提下,改变隔热隔声层的铺设方式和材料密度对壁板隔声性能影响较小,但在蒙皮内侧粘贴阻尼层能在一定频段范围提高壁板隔声性能;将优化的壁板构型应用到飞机后舱段侧壁板,舱内噪声水平可降低约3 dB。     

基于Kriging代理模型的飞行器结构刚度气动优化设计

大飞机具有轻质大柔性特点,使得气动/结构耦合作用增强,在设计过程中需要考虑这种耦合效应,直接调用CSD/CFD方法计算周期长,无法满足工程需要.代理模型方法由于能显著提高工程优化设计的效率,已广泛应用于飞行器气动外形优化设计中.采用Kriging方法建立代理模型,通过求解EI函数最大值得到需添加的样本点以更新代理模型,提高代理模型的拟合精度,结合改进的粒子群最优化方法对大飞机的结构刚度进行了优化设计.结果表明,该优化方法能够处理复杂目标的全局优化问题,在保证升力系数及纵向稳定性能不恶化的前提下,降低飞机巡航状态的飞行阻力.      

Aircraft noise: accounting for changes in air traffic with time of day

Aircraft noise contours are estimated using model calculations and, due to their impact on land use planning, they need to be highly accurate. During night time, not only the number and dominant types of aircraft may differ from daytime but also the flight paths flown may differ. To determine to which detail these variations in flight paths need to be considered, calculations were performed exemplarily for two airports using all available radar data over 1 year, taking into account their changes over the day. The results of this approach were compared with results of a simpler approach which does not consider such changes. While both calculations yielded similar results for the day and close to the airport, differences increased with distance as well as with the period of day (day相似文献   

A multi-input multi-output adaptive feed-forward controller for vibration alleviation on a large blended wing body airliner

Turbulent atmosphere, gusts, and manoeuvres significantly excite aircraft rigid body motions and structural vibrations, which leads to reduced ride comfort and increased structural loads. In particular BWB (Blended Wing Body) aircraft configurations, while promising a significant fuel efficiency improvement compared to wing-tube configurations, exhibit severe sensitivity to gusts. In general, a flexible aircraft represents a lightly damped structure involving a large variety of uncertainties due to fuel mass variations during flight, control system nonlinearities, aerodynamic nonlinearities, and structural nonlinearities, to name just a few. Especially at the beginning of flight testing of a newly developed aircraft type, plant models generally require a lot of verification and adjustment based on obtained flight test data, before they can be used reliably for control law design. Adaptive control already is a well-established method for many active noise and vibration control problems, and thus is proposed here for application to the problem of gust load alleviation. However, safety requirements are significantly higher for gust load alleviation systems than for most noise and vibration control systems. This paper proposes a MIMO (Multi-Input Multi-Output) adaptive feed-forward controller for the alleviation of turbulence-induced rigid body motions and structural vibrations on aircraft. The major contribution to the research field of active noise and vibration control is the presentation of a detailed stability analysis of the MIMO adaptive algorithm in order to support potential certification of this method for a safety-critical application. Finally, the proposed MIMO adaptive feed-forward vibration controller is applied to a longitudinal flight dynamics model of a large flexible BWB airliner in order to verify the derived vibration controller on a challenging control problem.     

Application of frequency-domain linearized Euler solutions to the prediction of aft fan tones and comparison with experimental measurements on model scale turbofan exhaust nozzles

Although it is widely accepted that aircraft noise needs to be further reduced, there is an equally important, on-going requirement to accurately predict the strengths of all the different aircraft noise sources, not only to ensure that a new aircraft is certifiable and can meet the ever more stringent local airport noise rules but also to prioritize and apply appropriate noise source reduction technologies at the design stage. As the bypass ratio of aircraft engines is increased - in order to reduce fuel consumption, emissions and jet mixing noise - the fan noise that radiates from the bypass exhaust nozzle is becoming one of the loudest engine sources, despite the large areas of acoustically absorptive treatment in the bypass duct. This paper addresses this ‘aft fan’ noise source, in particular the prediction of the propagation of fan noise through the bypass exhaust nozzle/jet exhaust flow and radiation out to the far-field observer. The proposed prediction method is equally applicable to fan tone and fan broadband noise (and also turbine and core noise) but here the method is validated with measured test data using simulated fan tones. The measured data had been previously acquired on two model scale turbofan engine exhausts with bypass and heated core flows typical of those found in a modern high bypass engine, but under static conditions (i.e. no flight simulation). The prediction method is based on frequency-domain solutions of the linearized Euler equations in conjunction with perfectly matched layer equations at the inlet and far-field boundaries using high-order finite differences. The discrete system of equations is inverted by the parallel sparse solver MUMPS. Far-field predictions are carried out by integrating Kirchhoff's formula in frequency domain. In addition to the acoustic modes excited and radiated, some non-acoustic waves within the cold stream-ambient shear layer are also captured by the computations at some flow and excitation frequencies. By extracting phase speed information from the near-field pressure solution, these non-acoustic waves are shown to be convective Kelvin-Helmholtz instability waves. Strouhal numbers computed along the shear layer, based on the local momentum thickness also confirm this in accordance with Michalke's instability criterion for incompressible round jets with a similar shear layer profile. Comparisons of the computed far-field results with the measured acoustic data reveal that, in general, the solver predicts the peak sound levels well when the farfield is dominated by the in-duct target mode (the target mode being the one specified to the in-duct mode generator). Calculations also show that the agreement can be considerably improved when the non-target modes are also included, despite their low in-duct levels. This is due to the fact that each duct mode has its own distinct directionality and a non-target low level mode may become dominant at angles where the higher-level target mode is directionally weak. The overall agreement between the computations and experiment strongly suggests that, at least for the range of mean flows and acoustic conditions considered, the physical aeroacoustic radiation processes are fully captured through the frequency-domain solutions to the linearized Euler equations and hence this could form the basis of a reliable aircraft noise prediction method.     

Combining a theoretical approach and practical considerations for establishing aircraft noise charge schemes

This research has developed a systematic aircraft noise charge scheme, based on noise social costs, with a view to its application in Taiwan. The paper starts with a brief review of current structures and applications of noise charges, a market-based measure, in mitigating aircraft noise worldwide. The evaluation of aircraft noise social cost is an attempt at putting noise nuisance into monetary terms. The total and average noise social cost per flight at one airport is clearly different from another, depending mainly on the size of the noise contour and the number of residents affected. This research estimates the average noise social costs at various airports, using nine Taiwanese airports as case studies. Depending on the marginal impact of a flight and the mixture of aircraft types at each airport, the noise social cost per landing and take-off is then estimated for different aircraft types. The results of this study can inform airport, airline and local administration policies for taking environmental concerns into account when setting up noise charges, revising noise insulation schemes, and developing strategies for airport expansion and airline operations.     

A novel algorithm for solving optimal path planning problems based on parametrization method and fuzzy aggregation

In this Letter a new approach for solving optimal path planning problems for a single rigid and free moving object in a two and three dimensional space in the presence of stationary or moving obstacles is presented. In this approach the path planning problems have some incompatible objectives such as the length of path that must be minimized, the distance between the path and obstacles that must be maximized and etc., then a multi-objective dynamic optimization problem (MODOP) is achieved. Considering the imprecise nature of decision maker's (DM) judgment, these multiple objectives are viewed as fuzzy variables. By determining intervals for the values of these fuzzy variables, flexible monotonic decreasing or increasing membership functions are determined as the degrees of satisfaction of these fuzzy variables on their intervals. Then, the optimal path planning policy is searched by maximizing the aggregated fuzzy decision values, resulting in a fuzzy multi-objective dynamic optimization problem (FMODOP). Using a suitable t-norm, the FMODOP is converted into a non-linear dynamic optimization problem (NLDOP). By using parametrization method and some calculations, the NLDOP is converted into the sequence of conventional non-linear programming problems (NLPP). It is proved that the solution of this sequence of the NLPPs tends to a Pareto optimal solution which, among other Pareto optimal solutions, has the best satisfaction of DM for the MODOP. Finally, the above procedure as a novel algorithm integrating parametrization method and fuzzy aggregation to solve the MODOP is proposed. Efficiency of our approach is confirmed by some numerical examples.     

A path model of aircraft noise annoyance

This paper describes the development and testing of a path model of aircraft noise annoyance by using noise and social survey data collected in the vicinity of Toronto International Airport. Path analysis is used to estimate the direct and indirect effects of seventeen independent variables on individual annoyance. The results show that the strongest direct effects are for speech interference, attitudes toward aircraft operations, sleep interruption and personal sensitivity to noise. The strongest indirect effects are for aircraft L_eq(24) and sensitivity. Overall the model explains 41% of the variation in the annoyance reported by the 673 survey respondents. The findings both support and extend existing statements in the literature on the antecedents of annoyance.     

Robust active noise control in the loadmaster area of a military transport aircraft

The active noise control (ANC) method is based on the superposition of a disturbance noise field with a second anti-noise field using loudspeakers and error microphones. This method can be used to reduce the noise level inside the cabin of a propeller aircraft. However, during the design process of the ANC system, extensive measurements of transfer functions are necessary to optimize the loudspeaker and microphone positions. Sometimes, the transducer positions have to be tailored according to the optimization results to achieve a sufficient noise reduction. The purpose of this paper is to introduce a controller design method for such narrow band ANC systems. The method can be seen as an extension of common transducer placement optimization procedures. In the presented method, individual weighting parameters for the loudspeakers and microphones are used. With this procedure, the tailoring of the transducer positions is replaced by adjustment of controller parameters. Moreover, the ANC system will be robust because of the fact that the uncertainties are considered during the optimization of the controller parameters. The paper describes the necessary theoretic background for the method and demonstrates the efficiency in an acoustical mock-up of a military transport aircraft.     

飞机机体表面声压及舱内降噪优化设计

本文以某型客机为研究对象,从飞行试验数据分析和声学建模两方面研究机体表面声压分布及其对舱内壁板近场辐射声压的影响。首先根据试飞数据分析了机体表面声压分布,然后利用统计能量法建立飞机客舱中后段的声学模型,以试飞数据作为声源输入,研究机体表面声压分布对客舱内部壁板附近声压分布的影响,并在此基础上提出优化设计方案,通过模型验证优化方案的有效性。试飞数据表明：机体表面声压在后应急门前方、靠近地板处最大;巡航速度升高,声压级较大区域的面积随之增加;巡航高度和发动机N1N2频率变化对机体表面声压级分布无明显影响。仿真数据表明：仅蒙皮结构无法有效降低客舱噪声;对声学降噪包进行优化能增加壁板隔声量,降低舱内声压。     

Optimal Siting of Transfer Station Locations in a Metropolitan Solid Waste Management System

System analysis for solid waste management currently receives wide attention from both economic and environmental planners because of their complexity during the coordination of various management strategies. This paper deals with the development and application of an operational solid waste management model through a hierarchical approach, in which the siting problem of transfer stations in a large scale metropolitan region is decomposed into two different levels. This analytical approach encompasses a preliminary screening procedure using the Geographical Information System (GIS) and an optimization analysis by a mixed integer programming model. Four criteria are employed in the screening of initial candidate sites and the optimization of a solid waste collection, recycling, treatment, and disposal system is used to direct waste generation to existing or proposed transfer stations, treatment plants and disposal facilities at minimum cost. A case study in Taiwan shows that the optimal siting strategies of transfer stations can successfully reduce system direct cost and generate relatively reasonable operational programs.     

The effect of forward flight on the diffraction radiation of a high speed jet

This paper describes a theoretical modelling of the effect of aircraft flight on the diffractional generation of sound which occurs when shear layer turbulence convects at high speed past a trailing edge. This is relevant to the study of noise problems associated with blown flaps, powered lift and aerodynamic shielding devices. The analysis is conducted for a two-dimensional configuration at arbitrary subsonic flight velocity. It is concluded that in the absence of a Kutta condition at the trailing edge, the effect of flight results in a forward arc amplification of the diffraction radiation through a single Doppler factor on the linear acoustic pressure field. The forward arc lift in the field shape disappears when a Kutta condition is imposed. In all cases the intensity of the diffraction radiation at 90° to the flight path is diminished by forward motion of the aircraft.     

Stripe noise removal for infrared image by minimizing difference between columns

This paper introduces a novel approach to eliminate stripe noise in infrared images. The differences between bias voltages in column readout circuit of uncooled infrared sensors result in strong stripe noise which changes slowly in time. The problem can be solved by estimating the bias of each column of infrared images and correcting infrared images with the estimated biases. The bias estimation is translated into an energy optimization problem in the paper. The optimization aims to minimize difference between neighboring columns of images. Our approach can be processed on a single image, or in a recursive way in order to significantly reduce the computation in one frame time. Our approach is compared to the state-of-the-art the stripe noise removal method using realistic infrared images, and the experimental results show the effectiveness and efficiencies of our proposed approach.     

Effect of background noise levels on community annoyance from aircraft noise

A study of community annoyance caused by exposures to civil aircraft noise was carried out in 20 sites around Gimpo and Gimhae international airports to investigate the effect of background noise in terms of dose-effect relationships between aircraft noise levels and annoyance responses under real conditions. Aircraft noise levels were mainly measured using airport noise monitoring systems, B&K type 3597. Social surveys were administered to people living within 100 m of noise measurement sites. The question relating to the annoyance of aircraft noise was answered on an 11-point numerical scale. The randomly selected respondents, who were aged between 18 and 70 years, completed the questionnaire independently. In total, 753 respondents participated in social surveys. The result shows that annoyance responses in low background noise regions are much higher than those in high background noise regions, even though aircraft noise levels are the same. It can be concluded that the background noise level is one of the important factors on the estimation of community annoyance from aircraft noise exposure.     

Propeller aircraft interior noise model,part II: Scale-model and flight-test comparisons

Part I [1] of this paper contains the theory used to create a basic propeller aircraft interior noise model. The model predicts tonal levels of blade passage harmonics in the cabin of a propeller driven aircraft. Part II presents the results of validation studies based on scale-model and flight comparisons.     

Noise assessment and mitigation schemes for Hurghada airport

In recent years, concern over airport noise and its impact on surrounding communities has been spurred by a continual growth in air traffic together with urban development in close proximity to many airports around the world. This paper aims at studying the case of Hurghada airport, Egypt, with a focus on evaluating, both theoretically and practically, the airport noise and its impact on the city of Hurghada. Extensive field measurements of aircraft noise were undertaken at key locations in the city, including points lying within the premises of the Hurghada airport. The aircraft noise was also modeled using the integrated noise model (INM) in order to simulate the current and future noise levels based upon the anticipated steady increase in flight operations. Such forecasts are of particular importance for Hurghada as the number of flights is expected to grow steadily over the next decade, accompanied with an increase in urban growth for coastal resorts. Based on the actual measurements and computer simulation, noise mitigation schemes are suggested to alleviate current and future impacts.     

飞行试验中军用1553B总线的实时采集技术

针对飞行试验中飞机结构件的动态变形测量问题,提出了一种基于图像的测量方法,对其中涉及的关键技术进行了研究。采用10参数模型非线性成像模型补偿摄像机系统误差,引入摄像机动态校准算法,使摄像机标校重投影误差小于0.03pixel;采用编码标志作为测量标志,提高了图像自动识别和匹配效率;采用双像机交会测量计算测量标志位移变形量可达到0.15mm/1m。实验证明,该方法满足飞行试验中飞机结构件动态变形要求。