CEAS/AIAA/ICASE/NASA Langley International Forum on Aeroelasticity and Structural Dynamics 1999

These proceedings represent a collection of the latest advances in aeroelasticity and structural dynamics from the world community. Research in the areas of unsteady aerodynamics and aeroelasticity, structural modeling and optimization, active control and adaptive structures, landing dynamics, certification and qualification, and validation testing are highlighted in the collection of papers. The wide range of results will lead to advances in the prediction and control of the structural response of aircraft and spacecraft

CEAS/AIAA/ICASE/NASA Langley International Forum on Aeroelasticity and Structural Dynamics 1999

The proceedings of a workshop sponsored by the Confederation of European Aerospace Societies (CEAS), the American Institute of Aeronautics and Astronautics (AIAA), the National Aeronautics and Space Administration (NASA), Washington, D.C., and the Institute for Computer Applications in Science and Engineering (ICASE), Hampton, Virginia, and held in Williamsburg, Virginia June 22-25, 1999 represent a collection of the latest advances in aeroelasticity and structural dynamics from the world community. Research in the areas of unsteady aerodynamics and aeroelasticity, structural modeling and optimization, active control and adaptive structures, landing dynamics, certification and qualification, and validation testing are highlighted in the collection of papers. The wide range of results will lead to advances in the prediction and control of the structural response of aircraft and spacecraft

Особенности расчета бафтинговых явлений при моделировании обтекания летательного аппарата с использованием открытого пакета OpenFOAM

In this paper, the preliminary results of computational modeling of an aircraft with the airbrake deployed are presented. The calculations were performed with OpenFOAM software package. The results outlined are a part of a research project to optimise aircraft performance using a perforated airbrake. Within this stage of the project OpenFOAM software package with hybrid RANS-LES approach was tested in respect to a given configuration of the aircraft, airbrake and then has been compared with the test data. For the worst case the amplitude of the peak force acting on the tail fin can be up to 6 times higher than the average value without airbrake deployed. To reduce unsteady loads acting on the tailfin, perforation of the airbrake was proposed.Показана возможность применения открытого пакета OpenFOAM и разработанных на его основе методик расчета нестационарных вихревых течений при исследовании обтекания летательного аппарата. Представлены результаты численных расчетов аэродинамических характеристик тормозного щитка, установленного на фюзеляж перспективного маневренного самолета. Описана разработанная гибридная модель турбулентности с применением RANS и LES подходов. Проведена оценка возмущений, обусловленных наличием тормозного щитка, на килевой стабилизатор летательного аппарата. Для снижения динамических нагрузок предложен тормозной щиток с перфорацией

Unsteady aerodynamics for aeroelastic applications using the impulse response method

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2000.Also available online at the MIT Theses Online homepage .Includes bibliographical references (p. 157-163).Aeroelasticity is a critical issue in the design of aircraft and other aerospace vehicles, particularly those with highly flexible components. A reliable but efficient analysis tool is required to aid decision-making in the preliminary design phase. This thesis focuses on the unsteady aerodynamics component of the total aeroelastic system. Classically unsteady aerodynamics has been grounded on the Theodorsen function, which identifies the response of a 2-D wing section to harmonic pitch and plunge oscillations. Recently, however, the Aerodynamic Impulse Response has emerged, identifying a more fundamental aerodynamic response of a discrete-time system as that to a unit impulse. With this response, the response to any motion in the time domain can be easily predicted. This thesis examines the Aerodynamic Impulse Response method using an aerodynamic panel code, PMARC, to obtain impulse responses. The basic formulation of the method is limited to rigid-body analyses and is thus of limited use to aeroelastic studies. To this end, the method is extended to flexible-body responses by considering impulse distribution functions that are related to structural mode shapes of the body. Both linear and nonlinear responses are considered: the former uses convolution to generate arbitrary responses, the later the Volterra series. Linear results for both rigid and flexible bodies are encouraging. Predictions for a range of input motions closely match the unsteady response from PMARC for the same motion. However, for harmonic motion accuracy erodes for f [Delta] t < 0.05, limiting the frequency range over which the model is accurate. Nonlinear responses are erratic and further study is required.by Randal Edmund Guendel.S.M

Time marching analysis of flutter using computational fluid dynamics

The maturity of simulation codes for aerodynamics (CFD) and structures (CSD) now leads to high fidelity computations of single discipline problems. The problem of aircraft flutter involves the coupling of aerodynamics and structures and has led to an interest in coupling CFD and CSD codes. There is strong motivation to couple existing codes to simulate this problem to avoid developing new methods since current single discipline methods are both well established and differ in their formulation (Eulerian fluids descriptions based on finite volume methods and Lagrangian finite element methods for structures). Recent work on the sequencing of codes has addressed the time sequencing issue which can be resolved by an iterative scheme to make sure that both simulations advance simultaneously in time. The regeneration of volume grids around a deforming geometry has also received attention.A third problem involves the passing of loads and displacement information between the fluid and structural surface grids. These grids will not in general coincide and it is likely that they will not even lie on the same surface. This thesis considers this problem and evaluates several existing and proposed solutions from the point of view of geometrical considerations and time marching flutter analysis. The test cases considered are for the AGARD 445.6 wing and the MDO wing. A boundary element formulation is also considered both for the elimination of the transfer problem and also a transformation method.A successful evaluation of the influence of the transformation method on the time marching response of a wing in a transonic flow is given and is based on the decomposition of the transformation into two components inwards and outwards of the plane of the structural model's plane

Modeling and control of the aeroelastic response of highly flexible active wings

Thesis (E.A.A. and S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2000.Includes bibliographical references (p. 143-149).by Miguel Ortega-Morales.E.A.A.and S.M

Inverse determination of aircraft loading using artificial neural network analysis of structural response data with statistical methods

An artificial Neural Network (ANN) system has been developed that can analyse aircraft flight data to provide a reconstruction of the aerodynamic loads experienced by the aircraft during flight, including manoeuvre, buffet and distributed loading. For this research data was taken from the International Follow-On Structural Test Project (IFOSTP) F/A-18 fatigue test conducted by the Royal Australian Air Force and Canadian Forces. This fatigue test involved the simultaneous application of both manouevre and buffet loads using airbag actuators and shakers. The applied loads were representative of the actual loads experienced by an FA/18 during flight tests. Following an evaluation of different ANN types an Ellman network with three linear layers was selected. The Elman back-propagation network was tested with various parameters and structures. The network was trained using the MATLAB &#039;traingdx&#039; function with is a gradient descent with momentum and adaptive learning rate back-propagation algorithm. The ANN was able to provide a good approximation of the actual manoeuvre or buffet loads at the location where the training loads data were recorded even for input values which differ from the training input values. In further tests the ability to estimate distributed loading at locations not included in the training data was also demonstrated. The ANN was then modified to incorporate various methods for the calculation and prediction of output error and reliability Used in combination and in appropriate circumstances, the addition of these capabilities significantly increase the reliability, accuracy and therefore usefulness of the ANN system&#039;s ability to estimate aircraft loading.To demonstrate the ANN system&#039;s usefulness as a fatigue monitoring tool it was combined with a formulae for crack growth analysis. Results inficate the ANN system may be a useful fatigue monitoring tool enabling real time monitoring of aircraft critical components using existing strain gauge sensors

Optimization and integration of an electric ducted fan propulsion system

Rastući trend u pogledu istraživanja vezana za električni pogon nije zaobi- šao vazduhoplovnu granu industrije. Poslednjih godina, veliki broj svetskih kompanija i istraživačkih centara pokušava da razvije “zelen” pogon letelica. Takođe, ubrzanim razvojem električnih energetskih komponenti (elektromotori sa stalnim magnetima, litijum-polimerne baterije, mosfet tranzistori i sl.) stvorila se velika zastupljenost električnih vazduhoplovnih pogona u oblasti malih bespilotnih letelica. U skladu sa ovim trendom predmet istraživanja ove disertacije predstavljaju elektroventilatorski sistemi propulzora. U okviru istraživanja izvršen je detaljan pregled literature vezane za ventilatorske propulzore nakon čega su predstavljeni matematički modeli pojedinih komponen- ti sistema propulzora. Takođe su predstavljene i metode parametrizacije geomet- rijskog oblika propulzora B splajnovima i CST metodom kao i metaheuristički metodi optimizacije: genetski algoritmi i metod roja čestica. Pomoću definisanih modela i metoda razvijena je metodologija optimizaci- je elektroventilatorskog sistema propulzora koja je predstavljena kroz tri poje- dinačna primera kao i kroz integrisani primer optimizacije i integracije pro- pulzora na malu bespilotnu VTOL letelicu. Optimizacijom postojećeg propulzo- ra ukazano je na mogućnost poboljšanja njegovih performansi za određeni režim rada a razvijena je i metodologija za višekriterijumsku optimizaciju propulzora pogonjenim električnim pogonom za čije potrebe je stvorena i baza komercijalno dostupnih komponenata.The growing trend in terms of electric drive research did not bypass the aerospace industry. In recent years, a large number of world companies and research centers have been trying to develop a “green” aircraft propulsion system. Also, with the rapid development of electric power components (permanent magnet motors, lithium-polymer batteries, MOSFET transistors etc.) there is a large representation of electric aircraft propulsion in the field of small UAVs. In line with this trend the subject of research of this dissertation are electric ducted fan propulsion systems. Within the research a detailed review of literature considering fan propulsion systems is done after which the mathematical models of the propulsion system individual components are presented. Also, the methods for geometric shape parameterization via B-Splines and CST as well as the metaheuristic optimization methods: genetic algorithms and particle swarm optimization are presented. Using the defined methods and models an electric ducted fan optimization methodology is developed which is presented through three individual examples as well as an integral example of a small VTOL aircraft propulsion system optimization and integration. By the optimization of an existing propulsor the possibility of improving its performance for a certain design point is shown while a multiobjective optimization methodology of a propulsion system which is electrically driven is also developed for whose needs a database of commercially available components was created. For the purpose of experimental investigation, a propulsion test rig was developed with which the influence of the inlet geometry on a commercially available fan is examined and a numerical analysis via the finite volume method was done in order to obtain a qualitative insight in the propulsion system performance

Optimization and integration of an electric ducted fan propulsion system

Растући тренд у погледу истраживања везана за електрични погон није заоби- шао ваздухопловну грану индустрије. Последњих година, велики број светских компанија и истраживачких центара покушава да развије “зелен” погон летелица. Такође, убрзаним развојем електричних енергетских компоненти (електромотори са сталним магнетима, литијум-полимерне батерије, мосфет транзистори и сл.) створила се велика заступљеност електричних ваздухопловних погона у области малих беспилотних летелица. У складу са овим трендом предмет истраживања ове дисертације представљају електровентилаторски системи пропулзора. У оквиру истраживања извршен је детаљан преглед литературе везане за вентилаторске пропулзоре након чега су представљени математички модели појединих компонен- ти система пропулзора. Такође су представљене и методе параметризације геомет- ријског облика пропулзора Б сплајновима и ЦСТ методом као и метахеуристички методи оптимизације: генетски алгоритми и метод роја честица. Помоћу дефинисаних модела и метода развијена је методологија оптимизаци- је електровентилаторског система пропулзора која је представљена кроз три поје- диначна примера као и кроз интегрисани пример оптимизације и интеграције про- пулзора на малу беспилотну ВТОЛ летелицу. Оптимизацијом постојећег пропулзо- ра указано је на могућност побољшања његових перформанси за одређени режим рада а развијена је и методологија за вишекритеријумску оптимизацију пропулзора погоњеним електричним погоном за чије потребе је створена и база комерцијално доступних компонената.The growing trend in terms of electric drive research did not bypass the aerospace industry. In recent years, a large number of world companies and research centers have been trying to develop a “green” aircraft propulsion system. Also, with the rapid development of electric power components (permanent magnet motors, lithium-polymer batteries, MOSFET transistors etc.) there is a large representation of electric aircraft propulsion in the field of small UAVs. In line with this trend the subject of research of this dissertation are electric ducted fan propulsion systems. Within the research a detailed review of literature considering fan propulsion systems is done after which the mathematical models of the propulsion system individual components are presented. Also, the methods for geometric shape parameterization via B-Splines and CST as well as the metaheuristic optimization methods: genetic algorithms and particle swarm optimization are presented. Using the defined methods and models an electric ducted fan optimization methodology is developed which is presented through three individual examples as well as an integral example of a small VTOL aircraft propulsion system optimization and integration. By the optimization of an existing propulsor the possibility of improving its performance for a certain design point is shown while a multiobjective optimization methodology of a propulsion system which is electrically driven is also developed for whose needs a database of commercially available components was created. For the purpose of experimental investigation, a propulsion test rig was developed with which the influence of the inlet geometry on a commercially available fan is examined and a numerical analysis via the finite volume method was done in order to obtain a qualitative insight in the propulsion system performance

Nomad flutter and flow simulation acceleration for elastic wings

Aircraft are flexible aeroelastic structures. Therefore, in-flight they are susceptible to a self-induced oscillation known as flutter which can lead to rapid and catastrophic structural failure. The aircraft design process must ensure that flutter occurs beyond the flight envelope, yet the Government Aircraft Factories Nomad aircraft has occasionally experienced low speed flutter involving its flaperon. Past attempts to investigate the Nomad’s flaperon flutter were unsuccessful. Consequently, not much is known about the critical flutter mode except that it occurs upon landing at a speed of about 100 knots. The objective of this research was to make a contribution towards the knowledge needed to help resolve the Nomad&#039;s flutter. The scope of this work was limited to applying computational methods rather than physical experiments. A nonlinear aeroelastic simulation was deemed necessary for an accurate flutter analysis with the Nomad’s wing geometry in its landing configuration. However, nonlinear aeroelastic methods need significant development in many areas before they can be applied to problems like the Nomad. In particular, the nonlinear aerodynamics component of nonlinear aeroelastic simulations was identified as critical area. Hence, the focus of the research work related to nonlinear computational fluid dynamics (CFD) and more specifically, turbulence modelling, grid generation and the computational cost involved. Flow phenomena around high-lift wings, like the Nomad&#039;s, are not well understood under take-off and landing conditions. Therefore, studying the local flowfield structures around the Nomad’s wing-flaperon landing configuration would be valuable. No such examination has been reported in the literature. The steady, two-dimensional flowfield around the Nomad&#039;s wing was simulated. Results showed separated regions behind the flaperon and main wing element, and attached flow elsewhere. Pressure distributions along the flaperon were strongly influenced by turbulence model. Thus, existing Reynolds-Averaged Navier–Stokes turbulence models, coupled with wall modelling, are unreliable for this problem. Field grid generation required for nonlinear aerodynamics computations can be laborious and may involve considerable computational resources, especially for moving geometries essential for aeroelastic simulations. Therefore, an efficient grid generation algorithm was developed. It generated a structured O-grid around a single arbitrarily shaped body in two and three dimensions by solving a system of elliptic Laplace or Poisson equations. This algorithm differs from others by implementing several acceleration techniques, including approximate factorisation and the method of false transients, to enhance the convergence rate. Computation times were drastically reduced relative to traditional methods. In nonlinear aeroelastic simulations, over 60% of the total computational time is expended on nonlinear CFD calculations (excluding grid generation). This cost can be reduced by exploiting rapidly advancing computer technology. In this work, the scaling performance of Intel’s first general purpose quad-core processor for personal computers was studied using a CFD problem. Using a two-dimensional Euler solver developed from scratch, the results showed speedups of 350% and 256% for coarse and fine grids, respectively