Aeroelasticity, Volume III

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

Deadline for manuscript submissions: closed (31 March 2022) | Viewed by 14529

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Guest Editor
Department of Mechanical and Aerospace Engineering, Politecnico di Torino, 10129 Turin, Italy
Interests: aeroelasticity; aircraft design; aerospace structural analysis
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Special Issue Information

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
Guest Editor

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Published Papers (4 papers)

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Research

25 pages, 6920 KiB  
Article
Influence of Fluid Viscosity and Compressibility on Nonlinearities in Generalized Aerodynamic Forces for T-Tail Flutter
by Dominik Schäfer
Aerospace 2022, 9(5), 256; https://doi.org/10.3390/aerospace9050256 - 09 May 2022
Cited by 1 | Viewed by 1650
Abstract
The numerical assessment of T-tail flutter requires a nonlinear description of the structural deformations when the unsteady aerodynamic forces comprise terms from lifting surface roll motion. For linear flutter, a linear deformation description of the vertical tail plane (VTP) out-of-plane bending results in [...] Read more.
The numerical assessment of T-tail flutter requires a nonlinear description of the structural deformations when the unsteady aerodynamic forces comprise terms from lifting surface roll motion. For linear flutter, a linear deformation description of the vertical tail plane (VTP) out-of-plane bending results in a spurious stiffening proportional to the steady lift forces, which is corrected by incorporating second-order deformation terms in the equations of motion. While the effect of these nonlinear deformation components on the stiffness of the VTP out-of-plane bending mode shape is known from the literature, their impact on the aerodynamic coupling terms involved in T-tail flutter has not been studied so far, especially regarding amplitude-dependent characteristics. This term affects numerical results targeting common flutter analysis, as well as the study of amplitude-dependent dynamic aeroelastic stability phenomena, e.g., Limit Cycle Oscillations (LCOs). As LCOs might occur below the linear flutter boundary, fundamental knowledge about the structural and aerodynamic nonlinearities occurring in the dynamical system is essential. This paper gives an insight into the aerodynamic nonlinearities for representative structural deformations usually encountered in T-tail flutter mechanisms using a CFD approach in the time domain. It further outlines the impact of geometrically nonlinear deformations on the aerodynamic nonlinearities. For this, the horizontal tail plane (HTP) is considered in isolated form to exclude aerodynamic interference effects from the studies and subjected to rigid body roll and yaw motion as an approximation to the structural mode shapes. The complexity of the aerodynamics is increased successively from subsonic inviscid flow to transonic viscous flow. At a subsonic Mach number, a distinct aerodynamic nonlinearity in stiffness and damping in the aerodynamic coupling term HTP roll on yaw is shown. Geometric nonlinearities result in an almost entire cancellation of the stiffness nonlinearity and an increase in damping nonlinearity. The viscous forces result in a stiffness offset with respect to the inviscid results, but do not alter the observed nonlinearities, as well as the impact of geometric nonlinearities. At a transonic Mach number, the aerodynamic stiffness nonlinearity is amplified further and the damping nonlinearity is reduced considerably. Here, the geometrically nonlinear motion description reduces the aerodynamic stiffness nonlinearity as well, but does not cancel it. Full article
(This article belongs to the Special Issue Aeroelasticity, Volume III)
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25 pages, 9738 KiB  
Article
Model Updating and Aeroelastic Correlation of a Scaled Wind Tunnel Model for Active Flutter Suppression Test
by Domenico Di Leone, Francesco Lo Balbo, Alessandro De Gaspari and Sergio Ricci
Aerospace 2021, 8(11), 334; https://doi.org/10.3390/aerospace8110334 - 07 Nov 2021
Cited by 3 | Viewed by 2799
Abstract
This article presents a modal correlation and update carried out on an aeroelastic wind tunnel demonstrator representing a conventional passenger transport aircraft. The aim of this work is the setup of a corresponding numerical model that is able to capture the flutter characteristics [...] Read more.
This article presents a modal correlation and update carried out on an aeroelastic wind tunnel demonstrator representing a conventional passenger transport aircraft. The aim of this work is the setup of a corresponding numerical model that is able to capture the flutter characteristics of a scaled aeroelastic model designed to investigate and experimentally validate active flutter suppression technologies. The work described in this paper includes different finite element modeling strategies, the results of the ground vibration test, and finally the strategies adopted for modal updating. The result of the activities is a three-dimensional hybrid finite element model that is well representative of the actual aeroelastic behavior identified during the wind tunnel test campaign and that is capable of predicting the flutter boundary with an error of 1.2%. This model will be used to develop active flutter suppression controllers, as well as to perform the sensitivity analyses necessary to investigate their robustness. Full article
(This article belongs to the Special Issue Aeroelasticity, Volume III)
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29 pages, 2363 KiB  
Article
Nonlinear Aeroelastic Simulations and Stability Analysis of the Pazy Wing Aeroelastic Benchmark
by Jonathan Hilger and Markus Raimund Ritter
Aerospace 2021, 8(10), 308; https://doi.org/10.3390/aerospace8100308 - 18 Oct 2021
Cited by 10 | Viewed by 2880
Abstract
The Pazy wing aeroelastic benchmark is a highly flexible wind tunnel model investigated in the Large Deflection Working Group as part of the Third Aeroelastic Prediction Workshop. Due to the design of the model, very large elastic deformations in the order of 50% [...] Read more.
The Pazy wing aeroelastic benchmark is a highly flexible wind tunnel model investigated in the Large Deflection Working Group as part of the Third Aeroelastic Prediction Workshop. Due to the design of the model, very large elastic deformations in the order of 50% span are generated at highest dynamic pressures and angles of attack in the wind tunnel. This paper presents static coupling simulations and stability analyses for selected onflow velocities and angles of attack. Therefore, an aeroelastic solver developed at the German Aerospace Center (DLR) is used for static coupling simulations, which couples a vortex lattice method with the commercial finite element solver MSC Nastran. For the stability analysis, a linearised aerodynamic model is derived analytically from the unsteady vortex lattice method and integrated with a modal structural model into a monolithic aeroelastic discrete-time state-space model. The aeroelastic stability is then determined by calculating the eigenvalues of the system’s dynamics matrix. It is shown that the stability of the wing in terms of flutter changes significantly with increasing deflection and is heavily influenced by the change in modal properties, i.e., structural eigenvalues and eigenvectors. Full article
(This article belongs to the Special Issue Aeroelasticity, Volume III)
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23 pages, 8338 KiB  
Article
A Parametric Study on the Aeroelasticity of Flared Hinge Folding Wingtips
by Rafic M. Ajaj, Erick I. Saavedra Flores, Mohammadreza Amoozgar and Jonathan E. Cooper
Aerospace 2021, 8(8), 221; https://doi.org/10.3390/aerospace8080221 - 10 Aug 2021
Cited by 11 | Viewed by 2853
Abstract
This paper presents a parametric study on the aeroelasticity of cantilever wings equipped with Flared Hinge Folding Wingtips (FHFWTs). The finite element method is utilized to develop a computational, low-fidelity aeroelastic model. The wing structure is modelled using Euler–Bernoulli beam elements, and unsteady [...] Read more.
This paper presents a parametric study on the aeroelasticity of cantilever wings equipped with Flared Hinge Folding Wingtips (FHFWTs). The finite element method is utilized to develop a computational, low-fidelity aeroelastic model. The wing structure is modelled using Euler–Bernoulli beam elements, and unsteady Theodorsen’s aerodynamic strip Theory is used for aerodynamic load predictions. The PK method is used to estimate the aeroelastic boundaries. The model is validated using three rectangular, cantilever wings whose properties are available in literature. Then, a rectangular, cantilever wing is used to study the effect of folding wingtips on the aeroelastic response and stability boundaries. Two scenarios are considered for the aeroelastic analysis. In the first scenario, the baseline, rectangular wing is split into inboard and outboard segments connected by a flared hinge that allows the outboard segment to fold. In the second scenario, a folding wingtip is added to the baseline wing. For both scenarios, the influence of fold angle, hinge-line angle (flare angle), hinge stiffness, tip mass and geometry are assessed. In addition, the load alleviation capability of FHFWT is evaluated when the wing encounters discrete (1-cosine) gusts. Finally, the hinge is assumed to exhibit cubic nonlinear behavior in torsion, and the effect of nonlinearity on the aeroelastic response is assessed and analyzed for three different cases. Full article
(This article belongs to the Special Issue Aeroelasticity, Volume III)
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