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Prof. Fernando Lau
IDMEC, Instituto Superior Técnico, Universidade de Lisboa

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0 Aeroacoustics
0 Aeroelasticity
0 Aeronautics
0 Aerospace
0 Conceptual Design

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morphing aircraft
Aeroelasticity
Aerospace
Conceptual Design

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Journal article
Published: 20 April 2021 in Mathematical and Computational Applications
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The objective of this work is to study the coupling of two efficient optimization techniques, Aerodynamic Shape Optimization (ASO) and Topology Optimization (TO), in 2D airfoils. To achieve such goal two open-source codes, SU2 and Calculix, are employed for ASO and TO, respectively, using the Sequential Least SQuares Programming (SLSQP) and the Bi-directional Evolutionary Structural Optimization (BESO) algorithms; the latter is well-known for allowing the addition of material in the TO which constitutes, as far as our knowledge, a novelty for this kind of application. These codes are linked by means of a script capable of reading the geometry and pressure distribution obtained from the ASO and defining the boundary conditions to be applied in the TO. The Free-Form Deformation technique is chosen for the definition of the design variables to be used in the ASO, while the densities of the inner elements are defined as design variables of the TO. As a test case, a widely used benchmark transonic airfoil, the RAE2822, is chosen here with an internal geometric constraint to simulate the wing-box of a transonic wing. First, the two optimization procedures are tested separately to gain insight and then are run in a sequential way for two test cases with available experimental data: (i) Mach 0.729 at α=2.31°; and (ii) Mach 0.730 at α=2.79°. In the ASO problem, the lift is fixed and the drag is minimized; while in the TO problem, compliance minimization is set as the objective for a prescribed volume fraction. Improvements in both aerodynamic and structural performance are found, as expected: the ASO reduced the total pressure on the airfoil surface in order to minimize drag, which resulted in lower stress values experienced by the structure.

ACS Style

Isaac Gibert Martínez; Frederico Afonso; Simão Rodrigues; Fernando Lau. A Sequential Approach for Aerodynamic Shape Optimization with Topology Optimization of Airfoils. Mathematical and Computational Applications 2021, 26, 34 .

AMA Style

Isaac Gibert Martínez, Frederico Afonso, Simão Rodrigues, Fernando Lau. A Sequential Approach for Aerodynamic Shape Optimization with Topology Optimization of Airfoils. Mathematical and Computational Applications. 2021; 26 (2):34.

Chicago/Turabian Style

Isaac Gibert Martínez; Frederico Afonso; Simão Rodrigues; Fernando Lau. 2021. "A Sequential Approach for Aerodynamic Shape Optimization with Topology Optimization of Airfoils." Mathematical and Computational Applications 26, no. 2: 34.

Journal article
Published: 18 November 2020 in Aerospace
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Recently, innovative aircraft designs were proposed to improve aerodynamic performance. Examples include high aspect ratio wings to reduce the aerodynamic induced drag to achieve lower fuel consumption. Such solution when combined with a lightweight structure may lead to aeroelastic instabilities such as flutter at lower air speeds compared to more conventional wing designs. Therefore, in order to ensure safe flight operation, it is important to study the aeroelastic behavior of the wing throughout the flight envelope. This can be achieved by either experimental or computational work. Experimental wind tunnel and scaled flight test models need to exhibit similar aeroelastic behavior to the full scale air vehicle. In this paper, three different aeroelastic scaling strategies are formulated and applied to a flexible high aspect-ratio wing. These scaling strategies are first evaluated in terms of their ability to generate reduced models with the intended representations of the aerodynamic, structural and inertial characteristics. Next, they are assessed in terms of their potential in representing the unsteady non-linear aeroelastic behavior in three different flight conditions. The scaled models engineered by exactly scaling down the internal structure suitably represent the intended aeroelastic behavior and allow the performance assessment for the entire flight envelope. However, since both the flight and wind tunnel models are constrained by physical and budgetary limitations, custom built structural models are more likely to be selected. However, the latter ones are less promising to study the entire flight envelope.

ACS Style

Frederico Afonso; Mónica Coelho; José Vale; Fernando Lau; Afzal Suleman. On the Design of Aeroelastically Scaled Models of High Aspect-Ratio Wings. Aerospace 2020, 7, 166 .

AMA Style

Frederico Afonso, Mónica Coelho, José Vale, Fernando Lau, Afzal Suleman. On the Design of Aeroelastically Scaled Models of High Aspect-Ratio Wings. Aerospace. 2020; 7 (11):166.

Chicago/Turabian Style

Frederico Afonso; Mónica Coelho; José Vale; Fernando Lau; Afzal Suleman. 2020. "On the Design of Aeroelastically Scaled Models of High Aspect-Ratio Wings." Aerospace 7, no. 11: 166.

Journal article
Published: 29 November 2019 in Journal of Cleaner Production
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The aeronautic industry is facing increasing pressure to design more efficient and sustainable aircraft to mitigate their impact on the environment. These solutions are mainly focused on: aerodynamics, structures/materials, propulsion and operations. This paper focuses on the potential of electric propulsion systems in different aircraft segments for reducing the environmental impact in the aircraft life cycle. With a twofold contribution and linking different areas, this study presents a methodological proposal for the environmental assessment of the propulsion system change in a consequential Life Cycle Assessment perspective. This methodology uses data from both a modified conceptual aircraft design adapted to hybrid-electric aircraft and a battery study. Results show not only the environmental impacts of the required battery systems for each aircraft segment in a life cycle perspective, but also in what contexts the hybrid-electric propulsion may be considered a best alternative environmentally when compared with fuel propulsion systems. For that, a sensitivity analysis illustrate the results for different electricity mix contexts and for different battery cell capacities. The main contribution for the overall life cycle impact is the process of charging a battery system, therefore the source of electricity generation is crucial for the environmental sustainability of a hybrid-electric aircraft.

ACS Style

João Ribeiro; Frederico Afonso; Inês Ribeiro; Bruna Ferreira; Hugo Policarpo; Paulo Peças; Fernando Lau. Environmental assessment of hybrid-electric propulsion in conceptual aircraft design. Journal of Cleaner Production 2019, 247, 119477 .

AMA Style

João Ribeiro, Frederico Afonso, Inês Ribeiro, Bruna Ferreira, Hugo Policarpo, Paulo Peças, Fernando Lau. Environmental assessment of hybrid-electric propulsion in conceptual aircraft design. Journal of Cleaner Production. 2019; 247 ():119477.

Chicago/Turabian Style

João Ribeiro; Frederico Afonso; Inês Ribeiro; Bruna Ferreira; Hugo Policarpo; Paulo Peças; Fernando Lau. 2019. "Environmental assessment of hybrid-electric propulsion in conceptual aircraft design." Journal of Cleaner Production 247, no. : 119477.

Review article
Published: 11 June 2019 in Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
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The need of the aerospace industry, at national or European level, of faster yet reliable computational fluid dynamics models is the main drive for the application of model reduction techniques. This need is linked to the time cost of high-fidelity models, rendering them inefficient for applications like multi-disciplinary optimization. With the goal of testing and applying model reduction to computational fluid dynamics models applicable to lifting surfaces, a bibliographical research covering reduction of nonlinear, dynamic, or steady models was conducted. This established the prevalence of projection and least mean squares methods, which rely on solutions of the original high-fidelity model and their proper orthogonal decomposition to work. Other complementary techniques such as adaptive sampling, greedy sampling, and hybrid models are also presented and discussed. These projection and least mean squares methods are then tested on simple and documented benchmarks to estimate the error and speed-up of the reduced order models thus generated. Dynamic, steady, nonlinear, and multiparametric problems were reduced, with the simplest version of these methods showing the most promise. These methods were later applied to single parameter problems, namely the lid-driven cavity with incompressible Navier–Stokes equations and varying Reynolds number, and the elliptic airfoil at varying angles of attack for compressible Euler flow. An analysis of the performance of these methods is given at the end of this article, highlighting the computational speed-up obtained with these techniques, and the challenges presented by multiparametric problems and problems showing point singularities in their domain.

ACS Style

Gonçalo Mendonça; Frederico Afonso; Fernando Lau. Model order reduction in aerodynamics: Review and applications. Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 2019, 233, 5816 -5836.

AMA Style

Gonçalo Mendonça, Frederico Afonso, Fernando Lau. Model order reduction in aerodynamics: Review and applications. Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering. 2019; 233 (15):5816-5836.

Chicago/Turabian Style

Gonçalo Mendonça; Frederico Afonso; Fernando Lau. 2019. "Model order reduction in aerodynamics: Review and applications." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 233, no. 15: 5816-5836.

Book chapter
Published: 01 January 2018 in Morphing Wing Technologies
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ACS Style

Frederico Afonso; Alessandro Airoldi; Salvatore Ameduri; Gianluca Amendola; Gennady A. Amiryants; Francesco Amoroso; Alexandre Antunes; Alfonso Apicella; Gianvito Apuleo; Maurizio Arena; Uwe T.P. Arnold; Silvestro Barbarino; Marco Bellucci; Paolo Bettini; Robert Blackwell; Ruxandra M. Botez; Miguel Á. Castillo Acero; Vasily Chedrik; Alexander Chedrik; Alexander Chevagin; Monica Ciminello; Antonio Concilio; Alessandro De Gaspari; Federico Martín De La Escalera; Luca Angelo Di Landro; Ignazio Dimino; José Lobo Do Vale; Antoine Dumont; Roman Efimov; Sergio Esposito; Yasser Essa; Rolf Evenblij; Alessandro Gilardelli; André Gratias; Teodor L. Grigorie; Generoso Iannuzzo; Fanil Ishmuratov; Vladimir Kulesh; Innokentiy Kursakov; Ksenia Kuruliuk; Svetlana Kuzmina; Fernando Lau; Thomas H. Lawrence; Leonardo Lecce; Grace Lima; Peter F. Lorber; Andreas Lühring; Alexander Lysenkov; Marco Magnifico; Vladimir Malenko; Victor Malyutin; Mihir P. Mistry; Christof Nagel; Maria Chiara Noviello; Felipe Odaguil; Antonio Pagano; Damiano Pasini; Modesto Pecora; Rosario Pecora; Fabian Peter; Mikhail Pronin; Francesco Rea; Sergio Ricci; Lorenzo Rossi; Salvatore Russo; Giuseppe Sala; Andrey Saprykin; Oliver Schorsch; Martin Schueller; Sergey Shalaev; Stefan Storm; Tobias Strobl; Eike Stumpf; Afzal Suleman; Viktor Timokhin; Maurizio Verrastro; Andrea Vigliotti; William A. Welsh; Matthew L. Wilbur; Mikhail Zichenkov. Contributors. Morphing Wing Technologies 2018, 1 .

AMA Style

Frederico Afonso, Alessandro Airoldi, Salvatore Ameduri, Gianluca Amendola, Gennady A. Amiryants, Francesco Amoroso, Alexandre Antunes, Alfonso Apicella, Gianvito Apuleo, Maurizio Arena, Uwe T.P. Arnold, Silvestro Barbarino, Marco Bellucci, Paolo Bettini, Robert Blackwell, Ruxandra M. Botez, Miguel Á. Castillo Acero, Vasily Chedrik, Alexander Chedrik, Alexander Chevagin, Monica Ciminello, Antonio Concilio, Alessandro De Gaspari, Federico Martín De La Escalera, Luca Angelo Di Landro, Ignazio Dimino, José Lobo Do Vale, Antoine Dumont, Roman Efimov, Sergio Esposito, Yasser Essa, Rolf Evenblij, Alessandro Gilardelli, André Gratias, Teodor L. Grigorie, Generoso Iannuzzo, Fanil Ishmuratov, Vladimir Kulesh, Innokentiy Kursakov, Ksenia Kuruliuk, Svetlana Kuzmina, Fernando Lau, Thomas H. Lawrence, Leonardo Lecce, Grace Lima, Peter F. Lorber, Andreas Lühring, Alexander Lysenkov, Marco Magnifico, Vladimir Malenko, Victor Malyutin, Mihir P. Mistry, Christof Nagel, Maria Chiara Noviello, Felipe Odaguil, Antonio Pagano, Damiano Pasini, Modesto Pecora, Rosario Pecora, Fabian Peter, Mikhail Pronin, Francesco Rea, Sergio Ricci, Lorenzo Rossi, Salvatore Russo, Giuseppe Sala, Andrey Saprykin, Oliver Schorsch, Martin Schueller, Sergey Shalaev, Stefan Storm, Tobias Strobl, Eike Stumpf, Afzal Suleman, Viktor Timokhin, Maurizio Verrastro, Andrea Vigliotti, William A. Welsh, Matthew L. Wilbur, Mikhail Zichenkov. Contributors. Morphing Wing Technologies. 2018; ():1.

Chicago/Turabian Style

Frederico Afonso; Alessandro Airoldi; Salvatore Ameduri; Gianluca Amendola; Gennady A. Amiryants; Francesco Amoroso; Alexandre Antunes; Alfonso Apicella; Gianvito Apuleo; Maurizio Arena; Uwe T.P. Arnold; Silvestro Barbarino; Marco Bellucci; Paolo Bettini; Robert Blackwell; Ruxandra M. Botez; Miguel Á. Castillo Acero; Vasily Chedrik; Alexander Chedrik; Alexander Chevagin; Monica Ciminello; Antonio Concilio; Alessandro De Gaspari; Federico Martín De La Escalera; Luca Angelo Di Landro; Ignazio Dimino; José Lobo Do Vale; Antoine Dumont; Roman Efimov; Sergio Esposito; Yasser Essa; Rolf Evenblij; Alessandro Gilardelli; André Gratias; Teodor L. Grigorie; Generoso Iannuzzo; Fanil Ishmuratov; Vladimir Kulesh; Innokentiy Kursakov; Ksenia Kuruliuk; Svetlana Kuzmina; Fernando Lau; Thomas H. Lawrence; Leonardo Lecce; Grace Lima; Peter F. Lorber; Andreas Lühring; Alexander Lysenkov; Marco Magnifico; Vladimir Malenko; Victor Malyutin; Mihir P. Mistry; Christof Nagel; Maria Chiara Noviello; Felipe Odaguil; Antonio Pagano; Damiano Pasini; Modesto Pecora; Rosario Pecora; Fabian Peter; Mikhail Pronin; Francesco Rea; Sergio Ricci; Lorenzo Rossi; Salvatore Russo; Giuseppe Sala; Andrey Saprykin; Oliver Schorsch; Martin Schueller; Sergey Shalaev; Stefan Storm; Tobias Strobl; Eike Stumpf; Afzal Suleman; Viktor Timokhin; Maurizio Verrastro; Andrea Vigliotti; William A. Welsh; Matthew L. Wilbur; Mikhail Zichenkov. 2018. "Contributors." Morphing Wing Technologies , no. : 1.

Book chapter
Published: 01 January 2018 in Morphing Wing Technologies
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ACS Style

José Lobo Do Vale; Frederico Afonso; Fernando Lau; Afzal Suleman. Span Morphing Concept: An Overview. Morphing Wing Technologies 2018, 125 -144.

AMA Style

José Lobo Do Vale, Frederico Afonso, Fernando Lau, Afzal Suleman. Span Morphing Concept: An Overview. Morphing Wing Technologies. 2018; ():125-144.

Chicago/Turabian Style

José Lobo Do Vale; Frederico Afonso; Fernando Lau; Afzal Suleman. 2018. "Span Morphing Concept: An Overview." Morphing Wing Technologies , no. : 125-144.

Journal article
Published: 01 August 2017 in Aerospace Science and Technology
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ACS Style

Frederico Afonso; José Vale; Fernando Lau; Afzal Suleman. Performance based multidisciplinary design optimization of morphing aircraft. Aerospace Science and Technology 2017, 67, 1 -12.

AMA Style

Frederico Afonso, José Vale, Fernando Lau, Afzal Suleman. Performance based multidisciplinary design optimization of morphing aircraft. Aerospace Science and Technology. 2017; 67 ():1-12.

Chicago/Turabian Style

Frederico Afonso; José Vale; Fernando Lau; Afzal Suleman. 2017. "Performance based multidisciplinary design optimization of morphing aircraft." Aerospace Science and Technology 67, no. : 1-12.

Journal article
Published: 11 May 2017 in The Aeronautical Journal
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A current trend in the aeronautic industry is to increase the wing aspect ratio to enhance aerodynamic efficiency by reducing the induced drag and thus reduce fuel consumption. Despite the associated benefits of a large aspect ratio, such as higher lift-to-drag ratios and range, commercial aircraft usually have a relatively low aspect ratio. This is partially explained by the fact that the wing becomes more flexible with increasing aspect ratio and thus more prone to large deflections, which can cause aeroelastic instability problems such as flutter. In this work, an aeroelastic study is conducted on a rectangular wing model of 20 m span and variable chord for a low subsonic speed condition to evaluate the differences between linear and non-linear static aeroelastic responses. Comparisons between linear and non-linear displacements, natural frequencies and flutter boundary are performed. An in-house non-linear aeroelastic framework was employed for this purpose. In this work, the influence of the aspect ratio and geometric non-linearity (highly deformed states) is assessed in terms of aeroelastic performance parameters: flutter speed and divergence speed. A nearly linear correlation of flutter speed difference (relative to linear analysis results) with vertical-tip displacement difference is observed. The flutter and divergence speeds vary substantially as the wing aspect ratio increases, and the divergence speeds always remain above the flutter speed. Furthermore, the flutter mechanism was observed to change as the wing chord is decreased.

ACS Style

Frederico Afonso; J. Vale; Éder Oliveira; Fernando Lau; A. Suleman. Non-linear aeroelastic response of high aspect-ratio wings in the frequency domain. The Aeronautical Journal 2017, 121, 858 -876.

AMA Style

Frederico Afonso, J. Vale, Éder Oliveira, Fernando Lau, A. Suleman. Non-linear aeroelastic response of high aspect-ratio wings in the frequency domain. The Aeronautical Journal. 2017; 121 (1240):858-876.

Chicago/Turabian Style

Frederico Afonso; J. Vale; Éder Oliveira; Fernando Lau; A. Suleman. 2017. "Non-linear aeroelastic response of high aspect-ratio wings in the frequency domain." The Aeronautical Journal 121, no. 1240: 858-876.

Journal article
Published: 01 April 2017 in Aerospace Science and Technology
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ACS Style

Christian Spada; Frederico Afonso; Fernando Lau; Afzal Suleman. Nonlinear aeroelastic scaling of high aspect-ratio wings. Aerospace Science and Technology 2017, 63, 363 -371.

AMA Style

Christian Spada, Frederico Afonso, Fernando Lau, Afzal Suleman. Nonlinear aeroelastic scaling of high aspect-ratio wings. Aerospace Science and Technology. 2017; 63 ():363-371.

Chicago/Turabian Style

Christian Spada; Frederico Afonso; Fernando Lau; Afzal Suleman. 2017. "Nonlinear aeroelastic scaling of high aspect-ratio wings." Aerospace Science and Technology 63, no. : 363-371.

Journal article
Published: 14 March 2017 in Structural and Multidisciplinary Optimization
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This study explores wing morphing for load alleviation as a means to reduce the required wing structural weight without compromising aircraft performance. A comparative study between the lift-to-drag ratio (L/D) performance of a fixed wing glider (FWG) and a cambered morphing wing glider (CMWG) is presented. Both aircraft are aero-structurally optimized for the best L/D for a given speed and payload mass. A combination of lifting-line theory and 2D viscous calculations is used for the aerodynamics and an equivalent beam model is employed for the structural analysis. Pull-up and -down maneuvers at 25 m/s and near stall angle of attack are assumed as critical load cases. Results of the FWG optimization are shown for several trimmed flight conditions with varying mass and velocity. Results are compared to the ones from the CMWG optimization and conclusions are drawn on the improvement in the L/D ratio throughout the flight envelope and on potential reductions in the wing structural mass due to the load alleviation strategy. The wing camber adaptation provides significant performance gains in a large range of flight speeds with negligible penalties in the low speeds range. However, maneuverability is penalized.

ACS Style

José Lobo Do Vale; Frederico Afonso; Éder Oliveira; Fernando Lau; Afzal Suleman. An optimization study on load alleviation techniques in gliders using morphing camber. Structural and Multidisciplinary Optimization 2017, 56, 435 -453.

AMA Style

José Lobo Do Vale, Frederico Afonso, Éder Oliveira, Fernando Lau, Afzal Suleman. An optimization study on load alleviation techniques in gliders using morphing camber. Structural and Multidisciplinary Optimization. 2017; 56 (2):435-453.

Chicago/Turabian Style

José Lobo Do Vale; Frederico Afonso; Éder Oliveira; Fernando Lau; Afzal Suleman. 2017. "An optimization study on load alleviation techniques in gliders using morphing camber." Structural and Multidisciplinary Optimization 56, no. 2: 435-453.

Review
Published: 01 February 2017 in Progress in Aerospace Sciences
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ACS Style

Frederico Afonso; José Lobo Do Vale; Éder Oliveira; Fernando Lau; Afzal Suleman. A review on non-linear aeroelasticity of high aspect-ratio wings. Progress in Aerospace Sciences 2017, 89, 40 -57.

AMA Style

Frederico Afonso, José Lobo Do Vale, Éder Oliveira, Fernando Lau, Afzal Suleman. A review on non-linear aeroelasticity of high aspect-ratio wings. Progress in Aerospace Sciences. 2017; 89 ():40-57.

Chicago/Turabian Style

Frederico Afonso; José Lobo Do Vale; Éder Oliveira; Fernando Lau; Afzal Suleman. 2017. "A review on non-linear aeroelasticity of high aspect-ratio wings." Progress in Aerospace Sciences 89, no. : 40-57.

Conference paper
Published: 05 January 2017 in 55th AIAA Aerospace Sciences Meeting
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A fast, linear scaling vortex method is presented to study inviscid incompressible flow problems involving one or more actuator disks. Building upon previous efforts that were limited to axi-symmetric flow cases, the proposed methodology is able to handle arbitrary configurations with no symmetry constraints. Applications include the conceptual study of wake interaction mechanisms in wind farms, and the correction of wind tunnel blockage effects in test sections of arbitrary shape. Actuator disks represent wind turbines through the shedding of a deformable vortex wake, discretized with a plaid of triangular distributed dipole singularities. An iterative method is adopted to align the wake with the local flow field, which is reconstructed from the vorticity field with a Green function approach. Interactions are computed with a Fast Multipole Method (FMM), effectively overcoming the quadratic scaling of computational time associated with traditional panel methods. When compared to direct computation, the use of an FMM algorithm reduced solution time by a factor 30 when studying the wake of a single actuator disk with 60000 panels. In the same case, the mass flux of the actuator streamtube was conserved to 0:002%. Finally, the presence of round and square impermeable walls around the actuator is considered to demonstrate the code applicability to wind tunnel wall interference correction problems

ACS Style

Simon Gamme; Gael de Oliveira; Daniele Ragni; Fernando Lau. A Fast Panel Code for Complex Actuator Disk Flows. 55th AIAA Aerospace Sciences Meeting 2017, 1 .

AMA Style

Simon Gamme, Gael de Oliveira, Daniele Ragni, Fernando Lau. A Fast Panel Code for Complex Actuator Disk Flows. 55th AIAA Aerospace Sciences Meeting. 2017; ():1.

Chicago/Turabian Style

Simon Gamme; Gael de Oliveira; Daniele Ragni; Fernando Lau. 2017. "A Fast Panel Code for Complex Actuator Disk Flows." 55th AIAA Aerospace Sciences Meeting , no. : 1.

Research article
Published: 25 November 2016 in Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
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The increase in wing aspect ratio is gaining interest among aircraft designers in conventional and joined-wing configurations due to the higher lift-to-drag ratios and longer ranges. However, current transport aircraft have relatively small aspect ratios due their increased structural stiffness. The more flexible the wing is more prone to higher deflections under the same operating condition, which may result in a geometrical nonlinear behavior. This nonlinear effect can lead to the occurrence of aeroelastic instabilities such as flutter sooner than in an equivalent stiffer wing. In this work, the effect of important stiffness (inertia ratio and torsional stiffness) and geometric (sweep and dihedral angles) design parameters on aeroelastic performance of a rectangular high aspect ratio wing model is assessed. The torsional stiffness was observed to present a higher influence on the flutter speed than the inertia ratio. Here, the decrease of the inertia ratio and the increase of the torsional stiffness results in higher flutter and divergence speeds. With respect to the geometric parameters, it was observed that neither the sweep angle nor the dihedral angle variations caused a substantial influence on the flutter speed, which is mainly supported by the resulting smaller variations in torsion and bending stiffness due to the geometric changes.

ACS Style

F Afonso; G Leal; J Vale; É Oliveira; Fernando Lau; A Suleman. The effect of stiffness and geometric parameters on the nonlinear aeroelastic performance of high aspect ratio wings. Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 2016, 231, 1824 -1850.

AMA Style

F Afonso, G Leal, J Vale, É Oliveira, Fernando Lau, A Suleman. The effect of stiffness and geometric parameters on the nonlinear aeroelastic performance of high aspect ratio wings. Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering. 2016; 231 (10):1824-1850.

Chicago/Turabian Style

F Afonso; G Leal; J Vale; É Oliveira; Fernando Lau; A Suleman. 2016. "The effect of stiffness and geometric parameters on the nonlinear aeroelastic performance of high aspect ratio wings." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 231, no. 10: 1824-1850.

Journal article
Published: 20 September 2016 in The Aeronautical Journal
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Commercial jets usually have relatively low-aspect-ratio wings, in spite of the associated benefits of increasing the wing aspect-ratio, such as higher lift-to-drag ratios and ranges. This is partially explained by the fact that the wing becomes more flexible by increasing the aspect-ratio that results in higher deflections which can cause aeroelastic instability problems such as flutter. An aeroelastic computational framework capable of evaluating the effects of geometric non-linearities on the aeroelastic performance of high-aspect-ratio wings has been developed and validated using numerical and experimental data. In this work, the aeroelastic performance of a base wing model with 20 m span and 1 m chord is analysed and the effect of changing the wing chord or the taper-ratio is determined. The non-linear static aeroelastic equilibrium solutions are compared in terms of drag polar, root bending moment and natural frequencies, and the change in the flutter speed boundary is assessed as a function of aspect-ratio using a time-marching approach.

ACS Style

A. Suleman; F. Afonso; José Lobo Do Vale; É. Oliveira; Fernando Lau. Non-linear aeroelastic analysis in the time domain of high-aspect-ratio wings: Effect of chord and taper-ratio variation. The Aeronautical Journal 2016, 121, 21 -53.

AMA Style

A. Suleman, F. Afonso, José Lobo Do Vale, É. Oliveira, Fernando Lau. Non-linear aeroelastic analysis in the time domain of high-aspect-ratio wings: Effect of chord and taper-ratio variation. The Aeronautical Journal. 2016; 121 (1235):21-53.

Chicago/Turabian Style

A. Suleman; F. Afonso; José Lobo Do Vale; É. Oliveira; Fernando Lau. 2016. "Non-linear aeroelastic analysis in the time domain of high-aspect-ratio wings: Effect of chord and taper-ratio variation." The Aeronautical Journal 121, no. 1235: 21-53.

Conference paper
Published: 02 January 2015 in 56th AIAA/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference
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ACS Style

Afzal Suleman; Frederico Afonso; Jose Vale; Fernando Lau. Performance Based MDO of a Joined-Wing Regional Transport Aircraft (For Challenges in the Design of Joined Wings SPECIAL SESSION). 56th AIAA/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference 2015, 1 .

AMA Style

Afzal Suleman, Frederico Afonso, Jose Vale, Fernando Lau. Performance Based MDO of a Joined-Wing Regional Transport Aircraft (For Challenges in the Design of Joined Wings SPECIAL SESSION). 56th AIAA/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference. 2015; ():1.

Chicago/Turabian Style

Afzal Suleman; Frederico Afonso; Jose Vale; Fernando Lau. 2015. "Performance Based MDO of a Joined-Wing Regional Transport Aircraft (For Challenges in the Design of Joined Wings SPECIAL SESSION)." 56th AIAA/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference , no. : 1.

Journal article
Published: 01 December 2014 in International Journal of Aeroacoustics
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The radiation of sound by surfaces in motion in a non-uniform flow, including the effects of reflections from obstacles on noise, is specified by an extension of the Kirchhoff integral that leads to a generalized multipole expansion that extends the classical series of spherical harmonics to account for the effects of ( i) the moving medium and ( ii) the rotating sound sources. The corresponding radiation integrals are evaluated analytically for an arbitrary source distribution along the blades of a propeller at an angular inflow. The effects of the incident flow and propeller rotation on the amplitude and phase of sound, e.g. through the retarded time, lead to an extension of the generating function for Legendre polynomials; this provides the representation of the acoustic field as the generalized multipolar series. Each generalized multipole sound field is shown to consist of a fundamental blade passng frequency (BPF) plus all harmonics, with directivities specified by integrals of Bessel functions, that are evaluated analytically. The theory is validated by comparison with noise measurements using two different model propellers in two distinct aeroacoustic wind tunnels. The experimental results are used to illustrate the principle of propeller noise synthesis, relating the radiated sound field to the sound source distribution.

ACS Style

Luis Campos; Fernando Lau. On a Generalized Multipole Expansion with Application to Propeller Design Synthesis. International Journal of Aeroacoustics 2014, 13, 553 -586.

AMA Style

Luis Campos, Fernando Lau. On a Generalized Multipole Expansion with Application to Propeller Design Synthesis. International Journal of Aeroacoustics. 2014; 13 (7-8):553-586.

Chicago/Turabian Style

Luis Campos; Fernando Lau. 2014. "On a Generalized Multipole Expansion with Application to Propeller Design Synthesis." International Journal of Aeroacoustics 13, no. 7-8: 553-586.

Book chapter
Published: 30 September 2014 in Engineering Optimization 2014
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ACS Style

F Sousa; Fernando Lau; A Suleman. Topology optimization of a wing structure. Engineering Optimization 2014 2014, 507 -512.

AMA Style

F Sousa, Fernando Lau, A Suleman. Topology optimization of a wing structure. Engineering Optimization 2014. 2014; ():507-512.

Chicago/Turabian Style

F Sousa; Fernando Lau; A Suleman. 2014. "Topology optimization of a wing structure." Engineering Optimization 2014 , no. : 507-512.

Book chapter
Published: 30 September 2014 in Engineering Optimization 2014
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ACS Style

J Vale; F Afonso; F Lau; A Suleman. Performance based MDO of a regional transport aircraft with a joined wing configuration. Engineering Optimization 2014 2014, 391 -396.

AMA Style

J Vale, F Afonso, F Lau, A Suleman. Performance based MDO of a regional transport aircraft with a joined wing configuration. Engineering Optimization 2014. 2014; ():391-396.

Chicago/Turabian Style

J Vale; F Afonso; F Lau; A Suleman. 2014. "Performance based MDO of a regional transport aircraft with a joined wing configuration." Engineering Optimization 2014 , no. : 391-396.

Journal article
Published: 01 July 2014 in Physics of Plasmas
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ACS Style

L. M. B. C. Campos; Fernando Lau. On the Debye–Hückel effect of electric screening. Physics of Plasmas 2014, 21, 072109 .

AMA Style

L. M. B. C. Campos, Fernando Lau. On the Debye–Hückel effect of electric screening. Physics of Plasmas. 2014; 21 (7):072109.

Chicago/Turabian Style

L. M. B. C. Campos; Fernando Lau. 2014. "On the Debye–Hückel effect of electric screening." Physics of Plasmas 21, no. 7: 072109.

Conference paper
Published: 10 January 2014 in 22nd AIAA/ASME/AHS Adaptive Structures Conference
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Afzal Suleman; Fernando Lau; Jose Vale; Frederico Afonso. Multidisciplinary Performance Based Optimization of Morphing Aircraft. 22nd AIAA/ASME/AHS Adaptive Structures Conference 2014, 1 .

AMA Style

Afzal Suleman, Fernando Lau, Jose Vale, Frederico Afonso. Multidisciplinary Performance Based Optimization of Morphing Aircraft. 22nd AIAA/ASME/AHS Adaptive Structures Conference. 2014; ():1.

Chicago/Turabian Style

Afzal Suleman; Fernando Lau; Jose Vale; Frederico Afonso. 2014. "Multidisciplinary Performance Based Optimization of Morphing Aircraft." 22nd AIAA/ASME/AHS Adaptive Structures Conference , no. : 1.