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Aeroelasticity, Volume II

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A special issue of Aerospace (ISSN 2226-4310). This special issue belongs to the section "Aeronautics".

Deadline for manuscript submissions: closed (15 November 2020) | Viewed by 49921

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Dr. Enrico Cestino

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Department of Mechanical and Aerospace Engineering, Politecnico di Torino, 10129 Turin, Italy
Interests: aeroelasticity; aircraft design; aerospace structural analysis
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Dear Colleagues,

Aviation’s contribution to global CO₂ emissions has come under scrutiny since the early 2000s. For this purpose, new aircraft configurations with greater energy efficiency are being developed. One way to increase energy efficiency is to reduce structural weight and the increase the wing aspect ratio.

The resulting slender, lighter, and highly flexible structures are prone to exhibit aeroelastic instabilities and require radically different structural and manufacturing concepts. The extensive use of anisotropic materials can play a crucial role in enhancing aircraft performance with no additional penalties on weight. To this end, aeroelastic tailoring is a fundamental tool. Potential enabling technologies are functionally graded materials (FGM), variable angle tow (VAT), curvilinear stiffeners, and foldable wings. The ongoing revolution in computer-aided design and manufacturing technologies has broken down barriers and paved the way for a variety of innovative solutions. The use of additive manufacturing (AM) can lead to numerous advantages either in terms of time and costs saving or the possibility of increasing the mould’s complexity and customization.

Uncertainties associated with the prediction of flight loads and manufacturing processes are not negligible, especially during the conceptual design phases due to the lack of information about the new product to be designed. Methods to quantify adequate design margins to account for the various sources of uncertainty are essential in order to satisfy safety levels imposed by regulations. Finally, experimental tests will provide the opportunity to verify the effectiveness of the design choices.

Research in this field is characterized by a highly multidisciplinary approach including theoretical, computational, and experimental studies.

Potential topics include but are not limited to the following:

New design concepts for future aircrafts;
Advanced numerical model development for aero-structural analyses and process simulation;
Optimization of composite structures;
Innovative morphing wing concepts to improve aeroservoelastic behaviour and active wing technology;
Uncertainty in composite aerostructures’ design;
Aeroelastic experimental tests.

Dr. Enrico Cestino
Collection Editor

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Related Special Issues

Aeroelasticity, Volume III in Aerospace (4 articles)
Aeroelasticity, Volume IV in Aerospace (5 articles)

Published Papers (10 papers)

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Research

20 pages, 8978 KiB

Open AccessArticle

Parametric Modeling of a Long-Range Aircraft under Consideration of Engine-Wing Integration

by Matthias Schulze, Jens Neumann and Thomas Klimmek

Aerospace 2021, 8(1), 2; https://doi.org/10.3390/aerospace8010002 - 23 Dec 2020

Cited by 6 | Viewed by 6083

Abstract

The purpose of this paper is to investigate the influence of the engine position and mass as well as the pylon stiffness on the aeroelastic stability of a long-range wide-body transport aircraft. As reference configuration, DLR’s (German Aerospace Center/Deutsches Zentrum für Luft und Raumfahrt) generic aircraft configuration DLR-D250 is taken. The structural, mass, loads, and optimization models for the reference and a modified configuration with different engine and pylon parameters are set up using DLR’s automatized aeroelastic design process cpacs-MONA. At first, the cpacs-MONA process with its capabilities for parametric modeling of the complete aircraft and in particular the set-up of a generic elastic pylon model is unfolded. Then, the influence of the modified engine-wing parameters on the flight loads of the main wing is examined. The resulting loads are afterward used to structurally optimize the two configurations component wise. Finally, the results of post-cpacs-MONA flutter analyses performed for the two optimized aircraft configurations with the different engine and pylon characteristics are discussed. It is shown that the higher mass and the changed position of the engine slightly increased the flutter speed. Although the lowest flutter speeds for both configurations occur at a flutter phenomenon of the horizontal tail-plane outside of the aeroelastic stability envelope. Full article

(This article belongs to the Special Issue Aeroelasticity, Volume II)

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29 pages, 12770 KiB

Open AccessArticle

Constructive Aerodynamic Interference in a Network of Weakly Coupled Flutter-Based Energy Harvesters

by Emmanuel Beltramo, Martín E. Pérez Segura, Bruno A. Roccia, Marcelo F. Valdez, Marcos L. Verstraete and Sergio Preidikman

Aerospace 2020, 7(12), 167; https://doi.org/10.3390/aerospace7120167 - 24 Nov 2020

Cited by 9 | Viewed by 3470

Abstract

Converting flow-induced vibrations into electricity for low-power generation has received growing attention over the past few years. Aeroelastic phenomena, good candidates to yield high energy performance in renewable wind energy harvesting (EH) systems, can play a pivotal role in providing sufficient power for extended operation with little or no battery replacement. In this paper, a numerical model and a co-simulation approach have been developed to study a new EH device for power generation. We investigate the problem focusing on a weakly aerodynamically coupled flutter-based EH system. It consists of two flexible wings anchored by cantilevered beams with attached piezoelectric layers, undergoing nonlinear coupled bending–torsion limit cycle oscillations. Besides the development of individual EH devices, further issues are posed when considering multiple objects for realizing a network of devices and magnifying the extracted power due to nonlinear synergies and constructive interferences. This work investigates the effect of various external conditions and physical parameters on the performance of the piezoaeroelastic array of devices. From the viewpoint of applications, we are most concerned about whether an EH can generate sufficient power under a variable excitation. The results of this study can be used for the design and integration of low-energy wind generation technologies into buildings, bridges, and built-in sensor networks in aircraft structures. Full article

(This article belongs to the Special Issue Aeroelasticity, Volume II)

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18 pages, 747 KiB

Open AccessFeature PaperArticle

On the Design of Aeroelastically Scaled Models of High Aspect-Ratio Wings

by Frederico Afonso, Mónica Coelho, José Vale, Fernando Lau and Afzal Suleman

Aerospace 2020, 7(11), 166; https://doi.org/10.3390/aerospace7110166 - 18 Nov 2020

Cited by 12 | Viewed by 4400

Abstract

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. Full article

(This article belongs to the Special Issue Aeroelasticity, Volume II)

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23 pages, 2607 KiB

Open AccessArticle

Static Aeroelasticity Using High Fidelity Aerodynamics in a Staggered Coupled and ROM Scheme

by Angelos Kafkas and George Lampeas

Aerospace 2020, 7(11), 164; https://doi.org/10.3390/aerospace7110164 - 17 Nov 2020

Cited by 9 | Viewed by 3874

Abstract

Current technology in evaluating the aeroelastic behavior of aerospace structures is based on the staggered coupling between structural and low fidelity linearized aerodynamic solvers, which has inherent limitations, although tried and trusted outside the transonic region. These limitations arise from the assumptions in the formulation of linearized aerodynamics and the lower fidelity in the description of the flowfield surrounding the structure. The validity of low fidelity aerodynamics also degrades fast with the deviation from a typical aerodynamic shape due to the inclusion of various control devices, gaps, or discontinuities. As innovative wings tend to become more flexible and also include a variety of morphing devices, it is expected that using low fidelity linearized aerodynamics in aeroelastic analysis will tend to induce higher levels of uncertainty in the results. An obvious solution to these issues is to use high fidelity aerodynamics. However, using high fidelity aerodynamics incurs a very high computational cost. Various formulations of reduced order models have shown promising results in reducing the computational cost. In the present work, the static aeroelastic behavior of three characteristic aeroelastic problems is obtained using both a full three-dimensional staggered coupled scheme and a time domain Volterra series based reduced order model (ROM). The reduced order model’s ability to remain valid for a wide range of dynamic pressures around a specific Mach number (and Reynolds number regime if viscous flow is considered) and the capability to modify structural parameters such as damping ratios and natural frequencies are highlighted. Full article

(This article belongs to the Special Issue Aeroelasticity, Volume II)

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25 pages, 5205 KiB

Open AccessFeature PaperArticle

Aerostructural Design Exploration of a Wing in Transonic Flow

by Nicolas P. Bons and Joaquim R. R. A. Martins

Aerospace 2020, 7(8), 118; https://doi.org/10.3390/aerospace7080118 - 14 Aug 2020

Cited by 16 | Viewed by 5212

Abstract

Multidisciplinary design optimization (MDO) has been previously applied to aerostructural wing design problems with great success. Most previous applications involve fine-tuning a well-designed aircraft wing. In this work, we broaden the scope of the optimization problem by exploring the design space of aerostructural wing design optimization. We start with a rectangular wing and optimize the aerodynamic shape and the sizing of the internal structure to achieve minimum fuel burn on a transonic cruise mission. We use a multi-level optimization procedure to decrease computational cost by 40%. We demonstrate that the optimization can transform the rectangular wing into a swept, tapered wing typical of a transonic aircraft. The optimizer converges to the same wing shape when starting from a different initial design. Additionally, we use a separation constraint at a low-speed, high-lift condition to improve the off-design performance of the optimized wing. The separation constraint results in a substantially different wing design with better low-speed performance and only a slight decrease in cruise performance. Full article

(This article belongs to the Special Issue Aeroelasticity, Volume II)

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14 pages, 4005 KiB

Open AccessArticle

Numerical/Experimental Validation of Thin-Walled Composite Box Beam Optimal Design

by Enrico Cestino, Giacomo Frulla, Paolo Piana and Renzo Duella

Aerospace 2020, 7(8), 111; https://doi.org/10.3390/aerospace7080111 - 31 Jul 2020

Cited by 2 | Viewed by 4267

Abstract

Thin-walled composite box beam structural configuration is representative of a specific high aspect ratio wing structure. The optimal design procedure and lay-up definition including appropriate coupling necessary for aerospace applications has been identified by means of “ad hoc” analytical formulation and by application of commercial code. The overall equivalent bending, torsional and coupled stiffness are derived and the accuracy of the simplified beam model is demonstrated by the application of Altair Optistruct. A simple case of a coupled cantilevered beam with load at one end is introduced to demonstrate that stiffness and torsion angle distribution does not always correspond to the trends that one would intuitively expect. The maximum of torsional stiffness is not obtained with fibers arranged at 45° and, at the maximum torsional stiffness, there is no minimum rotation angle. This observation becomes essential in any design process of composite structures where the constraints impose structural couplings. Furthermore, the presented theory is also extended to cases in which it is necessary to include composite/stiffened hybrid configurations. Good agreement has been found between the theoretical simplified beam model and numerical analysis. Finally, the selected composite configuration was compared to an experimental test case. The numerical and experimental validation is presented and discussed. A good correlation was found confirming the validity of the overall optimization for the optimal lay-up selection and structural configuration. Full article

(This article belongs to the Special Issue Aeroelasticity, Volume II)

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16 pages, 864 KiB

Open AccessArticle

Static Aeroelastic Beam Model Development for Folding Winglet Design

by Bereket Sitotaw Kidane and Enrico Troiani

Aerospace 2020, 7(8), 106; https://doi.org/10.3390/aerospace7080106 - 25 Jul 2020

Cited by 5 | Viewed by 5721

Abstract

Wing shape adaptability during flight is the next step towards the greening of aviation. The shape of the wing is typically designed for one cruise point or a weighted average of several cruise points. However, a wing is subjected to a variety of flight conditions, which results in the aircraft flying sub-optimally during a portion of the flight. Shape adaptability can be achieved by tuning the shape of the winglet during flight. The design challenge is to combine a winglet structure that is able to allow the required adaptable shape while preserving the structural integrity to carry the aerodynamic loads. The shape changing actuators must work against the structural strains and the aerodynamic loads. Analyzing the full model in the preliminary design phase is computationally expensive; therefore, it is necessary to develop a model. The goal of this paper is to derive an aeroelastic model for a wing and winglet in order to reduce the computational cost and complexity of the system in designing a folding winglet. In this paper, the static aeroelastic analysis is performed for a regional aircraft wing at sea level and service ceiling conditions with three degree and eight degree angle of attack. MSC Nastran Aeroelastic tool is used to develop a Finite Element Model (FEM), i.e., beam model and the aerodynamic loads are calculated based on a doublet lattice panel method (DLM). Full article

(This article belongs to the Special Issue Aeroelasticity, Volume II)

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11 pages, 2267 KiB

Open AccessArticle

Thermoelastic Response of Closed Cylindrical Shells in a Supersonic Gas Flow

by Marine Mikilyan

Aerospace 2020, 7(8), 103; https://doi.org/10.3390/aerospace7080103 - 22 Jul 2020

Cited by 4 | Viewed by 2864

Abstract

The work is devoted to the investigation of flutter oscillations and the stability of the closed cylindrical shell in supersonic gas flow in an inhomogeneous temperature field. It is assumed that supersonic gas flows on the outside of the shell with an unperturbed velocity U, directed parallel to the cylinder generatrix. Under the action of an inhomogeneous temperature field the shell bulges out, this deformed state is accepted as unperturbed, and the stability of this state is studied. The main nonlinear equations and relationships describing the behavior of the examined system are derived. The formulated boundary value problem is solved using the Galerkin method. The joint influence of the flow and the temperature field on the relationship between the amplitude of nonlinear oscillations of a cylindrical shell and the speed of the flowing stream is studied. The critical velocity values are calculated from the corresponding linear system and are given in tables. The numerical results show that: (a) the surrounding flow significantly affects the nature of the investigated relationship; (b) a certain interval of supersonic velocity exists where it is impossible to excite steady-state flutter oscillations (the silence zone); (c) the dependence of amplitude on the supersonic velocity can be either multivalued or single-valued. Full article

(This article belongs to the Special Issue Aeroelasticity, Volume II)

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19 pages, 3630 KiB

Open AccessArticle

Aeroelastic Wing Planform Design Optimization of a Flutter UAV Demonstrator

by Andreas Hermanutz and Mirko Hornung

Aerospace 2020, 7(4), 45; https://doi.org/10.3390/aerospace7040045 - 15 Apr 2020

Cited by 8 | Viewed by 6720

Abstract

In this work, a study to design a highly flexible flutter demonstrator for the development and testing of active flutter suppression is presented. Based on the UAV mission, a bi-objective design optimization problem can be formulated. The aeroelastic UAV characteristic and imposed constraints, defined by operational aspects and the structural integrity are described by surrogate modeling. Within the framework of the multi-criteria optimization, an approach to construct the equally spaced Pareto frontier with a new approach for non-convex problems is presented. An efficient Pareto configuration to meet a natural low speed and low frequency is identified and its main influencing design features are analyzed. Full article

(This article belongs to the Special Issue Aeroelasticity, Volume II)

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22 pages, 709 KiB

Open AccessArticle

Effect of Levels of Fidelity on Steady Aerodynamic and Static Aeroelastic Computations

by Adrien Crovato, Hugo S. Almeida, Gareth Vio, Gustavo H. Silva, Alex P. Prado, Carlos Breviglieri, Huseyin Guner, Pedro H. Cabral, Romain Boman, Vincent E. Terrapon and Grigorios Dimitriadis

Aerospace 2020, 7(4), 42; https://doi.org/10.3390/aerospace7040042 - 11 Apr 2020

Cited by 16 | Viewed by 5917

Abstract

Static aeroelastic deformations are nowadays considered as early as in the preliminary aircraft design stage, where low-fidelity linear aerodynamic modeling is favored because of its low computational cost. However, transonic flows are essentially nonlinear. The present work aims at assessing the impact of the aerodynamic level of fidelity used in preliminary aircraft design. Several fluid models ranging from the linear potential to the Navier–Stokes formulations were used to solve transonic flows for steady rigid aerodynamic and static aeroelastic computations on two benchmark wings: the Onera M6 and a generic airliner wing. The lift and moment loading distributions, as well as the bending and twisting deformations predicted by the different models, were examined, along with the computational costs of the various solutions. The results illustrate that a nonlinear method is required to reliably perform steady aerodynamic computations on rigid wings. For such computations, the best tradeoff between accuracy and computational cost is achieved by the full potential formulation. On the other hand, static aeroelastic computations are usually performed on optimized wings for which transonic effects are weak. In such cases, linear potential methods were found to yield sufficiently reliable results. If the linear method of choice is the doublet lattice approach, it must be corrected using a nonlinear solution. Full article

(This article belongs to the Special Issue Aeroelasticity, Volume II)

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