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Development of Efficient dynamic aeroelasticity Model for High Fidelity Pointing Accuracy Assessment of VLBI Earth-Based Radio Antennas

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INTERNATIONAL JOURNAL OF AERONAUTICAL AND SPACE SCIENCES 2020年第3期21卷 693-706页

作者： Nieto, Michelle Guzman Thomas, Paul, V ElSayed, Mostafa S. A. Saad, Mohamed Brown, Gary L. Hilliard, Lawrence M. Carleton Univ Ottawa ON K1S 5B6 Canada InterTron Solut Inc Vaudreuil Dorion PQ J7V 8P2 Canada NASA Goddard Space Flight Ctr Greenbelt MD 20771 USA

Modern Earth-based radio antennas of very-long-baseline interferometry system are furnished with robust control systems for their pointing control. Their pointing accuracy is critical to the quality of the radio wave-front captured. External disturbances, particularly those of wind gusts, produce a non-negligible dynamic aeroelastic response that degrades its pointing accuracy, and yet are not mitigated by the antenna's control system. In this paper, a high fidelity and efficient dynamic aeroelastic model of an earth-based antenna is developed which is used to study the effects of wind gusts on the antenna's pointing accuracy. Model order reduction of the antenna structural model is carried out using Craig-Bampton method taking into consideration the dominant modal characteristics of the antenna. The aerodynamic forces are approximated using the 2D Doublet-Lattice Method. The Davenport Spectrum is used to model aerodynamic turbulences near the earth surface. The developed dynamic aeroelastic model is employed to investigate the effects of discrete and random gusts on the pointing accuracy of the antenna. It is found that the deviation in the pointing angle is more prominent in thez(azimuth) direction and it displays a quadratic dependency with respect to the mean wind speed. This behavior is attributed to the inertial component of the aeroelastic response solution represented by the gravitational field acting on the center of gravity of the main reflector and the counterweights. The developed efficient aeroelastic model can be integrated into the antenna control system for its response prediction and mitigation.

关键词： VLBI Earth-based antenna Gust Devonport spectrum dynamic aeroelasticity Craig-Bampton Doublet-lattice method

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dynamic aeroelasticity of Wings with Tip Propeller by Using Navier-Stokes Equations

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AIAA JOURNAL 2019年第8期57卷 3200-3205页

作者： Guruswamy, Guru P. NASA Ames Res Ctr Computat Phys Branch Moffett Field CA 94035 USA

Aeroelastic computations are made for a flexible wing with a tip-propeller system designed for electric aircraft. Flow is modeled using the Navier-Stokes equations, and wing structures are modeled using plate finite elements. A time-accurate procedure is developed to embed the flexible wing in an overset grid topology along with rotating blades. Results are validated with existing data from wind-tunnel and potential flow computations. Aeroelastic responses are compared for the wing with and without a tip-propeller system. The present work extends the capabilities of current Navier-Stokes solvers to simulate the aeroelasticity of complex configurations and impacts the design of electric aircraft for urban transportation.

关键词： Navier Stokes Equations dynamic aeroelasticity Propeller Blades Rectangular Wing Wind Tunnel Tests Electric Aircraft Beam and Warming Scheme Potential Flow Reynolds Averaged Navier Stokes Wing Tip

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Modelling and analysis of two-dimensional static and dynamic aeroelasticity of Fish Bone Active Camber morphing aerofoils

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JOURNAL OF FLUIDS AND STRUCTURES 2024年 129卷

作者： Wu, Jun Woods, Benjamin K. S. Univ Bristol Dept Aerosp Engn Bristol BS8 1TR England Univ Oxford Dept Biol Oxford England

As a continuous and smooth morphing concept for aerofoils, the Fish Bone Active Camber (FishBAC) concept has demonstrated significant aerodynamic efficiency improvements over traditional hinged flaps. In this paper, to investigate the static and dynamic aeroelasticity of FishBAC aerofoils, an unsteady two dimensional coupled fluid-structure interaction model is developed, which includes the structural response of the FishBAC spine, skin, stringers, tendons and actuator, coupled to an unsteady aerodynamics model. The structural dynamic model is Timoshenko beam-theory-based, while the aerodynamic model is based on Peters' unsteady model. The static and dynamic aeroelasticity is studied after the model is validated. Results show that the increase in pulley rotational angle reduces the zero-lift angle of attack, while keeping the slope between the lift coefficient and angle of attack the same. A shorter morphing region closer to the trailing edge is beneficial for generating larger lift coefficient with the same tendon moment and angle of attack. Flutter occurs with the increase of the air speed. When the morphing end position is fixed at 0.9 chord, increasing the morphing length reduces the critical flutter speed significantly, with the second bending mode tending to drive instability. With the same morphing length, moving the morphing region closer to the leading edge increases the critical flutter speed, and the unstable mode changes from the second mode into the first mode.

关键词： Static aeroelasticity dynamic aeroelasticity Aerofoil morphing FishBAC concept Flutter

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High-Fidelity Gradient-Based Wing Structural Optimization Including Geometrically Nonlinear Flutter Constraint

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AIAA JOURNAL 2023年第7期61卷 3045-3061页

作者： Jonsson, Eirikur Riso, Cristina Monteiro, Bernardo Bahia Gray, Alasdair C. Martins, Joaquim R. R. A. Cesnik, Carlos E. S. Univ Michigan Dept Aerosp Engn 1320 Beal Ave Ann Arbor MI 48109 USA Univ Michigan Ann Arbor MI 48109 USA Georgia Inst Technol Daniel Guggenheim Sch Aerosp Engn 275 Ferst Dr Northwest Atlanta GA USA

Lightweight high-aspect-ratio wings make aircraft more energy efficient thanks to their lower induced drag. Because such wings exhibit large deflections, design optimization based on linear flutter analysis of the wing undeformed shape is inadequate. To address this issue, we develop a framework for integrating a geometrically nonlinear flutter constraint, which considers in-flight deflections, into a high-fidelity gradient-based structural optimization. The wing mass and stress constraints are evaluated on a linear built-up (detailed) finite element model to capture realistic structural features. The geometrically nonlinear flutter constraint is based on a condensed low-order beam representation of the built-up finite element model, which captures the impact of in-flight deflections with tractable computational effort for optimization. The flutter constraint is differentiated with respect to the detailed structural model sizing variables using the adjoint method to enable large-scale optimizations. The framework is demonstrated by minimizing the mass of a wingbox model subject to the geometrically nonlinear flutter constraint along with stress and adjacency constraints. The geometrically nonlinear flutter constraint adds a penalty of up to 60% of the baseline mass due to the impact of in-flight deflections on the flutter onset speed and its mechanism. In contrast, a linear flutter constraint evaluated on the undeformed wing adds a mass penalty of only 10%. This methodology can help design energy-efficient aircraft with high-aspect-ratio wings, which require geometrically nonlinear flutter analyses early in the design cycle.

关键词： Structural Design and Development Finite Element Modeling Structural dynamics and Characterization Aircraft Components and Structure Nonlinear Aeroelastic Systems Aircraft Wing Design Structural Optimization Flutter Analysis Nonlinear Structural dynamics dynamic aeroelasticity

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Comparison of static and dynamic the case of a highly flexible fluid-structure, interaction solutions in modern transport aircraft wing

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AEROSPACE SCIENCE AND TECHNOLOGY 2003年第2期7卷 121-133页

作者： Girodroux-Lavigne, P Grisval, JP Guillemot, S Henshaw, M Karlsson, A Selmin, V Smith, J Teupootahiti, E Winzell, B Off Natl Etud & Rech Aerosp DDSS MS F-92322 Chatillon France ALENIA AERONAUTICA I-10146 Turin Italy BAE Syst Aerodynam Technol Dept Brough E Yorks England DGT DTA IAP DASSAULT AVIAT F-92214 St Cloud France FFA Aeronaut Div FOI Swedish Def Res Agcy S-17290 Stockholm Sweden SAAB AB Flutter & Loads Dept S-58188 Linkoping Sweden

This paper describes the computational work performed by five of the fifteen partners in the Brite-Euram project UNSI, for the prediction of static aeroelastic configurations and dynamic flutter response at transonic conditions, using advanced time-domain fluid-structure coupling methods. The aerodynamic models, mechanical models, and coupling strategies implemented in the different solvers are presented. A code to code validation of the fluid-structure coupled solvers has been achieved in the case of the highly flexible MDO wing. The coupled codes have each been used first for the computation of steady state flow and static deformations at different flight conditions. The investigation of flutter has been carried out for off-design, heavy-cruise flight conditions, using time-consistent numerical simulations. dynamic responses have been recorded and compared for stable and flutter conditions. (C) 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved.

关键词： flutter prediction dynamic aeroelasticity static aeroelasticity fluid-structure coupling transonic flows numerical simulation

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Cyber-physical flexible wing for aeroelastic investigations of stall and classical flutter

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JOURNAL OF FLUIDS AND STRUCTURES 2016年 67卷 34-47页

作者： Fagley, Casey Seidel, Jurgen McLaughlin, Thomas US Air Force Acad Dept Aeronaut 2410 Fac Dr Colorado Springs CO 80840 USA

The fluid-structure interactions of a finite aspect ratio, cantilevered, flexible wing were investigated using a cyber-physical system to virtually augment the torsional dynamics of the wing. Cyber-physical systems (CPS), which have recently been pursued by a small number of research groups, have proven to be a very useful mechanism to interrogate the fluid-structure interaction parameter space. The premise of a CPS is to use dynamic feedback control to make a system behave according to desired equations of motion. Systems are composed of embedded hardware and software coupled with real-time computing to give the user the flexibility to quickly explore a range of structural parameters. With the advancement of modern control theory, robotics and embedded systems, CPSs integrate both simulation and physical properties into a smart structure which can be used to push the boundaries of research investigations. The CPS in this work allows for the investigation of dynamic aeroelastic instabilities of a three-dimensional, flexible, rectangular planform wing. Two dynamic instability regimes are observed: first, stall flutter, in which the torsional or pitch mode is excited through the dynamic stall process, and second, coupled (or classical) flutter, in which the pitch mode couples with the bending mode. By varying the torsional stiffness and therefore the frequency of torsional versus bending oscillations of the wing, both of these regimes can be attained at the same aerodynamic conditions using the CPS. (C) 2016 Elsevier Ltd. All rights reserved.

关键词： dynamic aeroelasticity Stall flutter Classical flutter Cyber-physical system

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Assessment of low-altitude atmospheric turbulence models for aircraft aeroelasticity

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JOURNAL OF FLUIDS AND STRUCTURES 2020年第0期95卷 102981-102981页

作者： Deskos, Georgios del Carre, Alfonso Palacios, Rafael Natl Renewable Energy Lab Natl Wind Technol Ctr Golden CO 80401 USA Imperial Coll London Dept Aeronaut London England

We investigate the dynamic aeroelastic response of large but slow aircraft in low-altitude atmospheric turbulence. To this end, three turbulence models of increasing fidelity, namely, the one-dimensional von Karman model, the two-dimensional Kaimal model and full three-dimensional wind fields extracted from large-eddy simulations (LES) are used to simulate ambient turbulence near the ground. Load calculations and flight trajectory predictions are conducted for a representative high-aspect-ratio wing aircraft, using a fully coupled nonlinear flight dynamics/aeroelastic model, when it operates in background atmospheric turbulence generated by the aforementioned models. Comparison of load envelopes and spectral content, on vehicles of varying flexibility, shows strong dependency between the selected turbulence model and aircraft aeroelastic response (e.g. 58% difference in the predicted magnitude of the wing root bending moment between LES and von Karman models). This is mainly due to the presence of large flow structures at low altitudes that have comparable dimensions to the vehicle, and which despite the relatively small wind speeds within the Earth boundary layer, result in overall high load events for slow-moving vehicles. Results show that one-dimensional models that do not capture those effects provide fairly non-conservative load estimates and are unsuitable for very flexible airframe design. (C) 2020 Elsevier Ltd. All rights reserved.

关键词： Atmospheric turbulence Gust loads Geometrically-nonlinear structures dynamic aeroelasticity Flight mechanics Large-eddy simulation

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Bifurcation-Diagram-Free Postflutter Response Constraint for Design Optimization

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AIAA JOURNAL 2023年第8期61卷 3449-3465页

作者： Riso, Cristina Cesnik, Carlos E. S. Epureanu, Bogdan I. Georgia Inst Technol Daniel Guggenheim Sch Aerosp Engn 275 Ferst Dr Northwest Atlanta 30332 Georgia Univ Michigan Dept Aerosp Engn 1320 Beal Ave Ann Arbor MI 48109 USA Univ Michigan Dept Mech Engn 2350 Hayward St Ann Arbor MI 48109 USA

This paper introduces a new metric to constrain postflutter responses of aeroelastic systems in design optimization. The new metric aggregates the recovery rate to equilibrium for a range of operating conditions, modes, and amplitudes, resulting in a scalar constraint that does not involve the bifurcation diagram. By generalizing damping-based flutter constraints, the formulation yields mathematical properties oriented toward gradient-based optimization. The approach is demonstrated by optimizing a typical section with a subcritical bifurcation using a gradient-based algorithm and finite-difference derivatives. The postflutter response constraint suppresses self-sustained oscillations below a given flow speed while minimizing the mass penalty, which avoids a conservative solution. This constraint can help design highly efficient aeroelastic systems with feasible postflutter dynamics. Future development of adjoint derivatives will enable large-scale gradient-based optimization.

关键词： Multidisciplinary Design Optimization Flutter Constraint Postflutter Response Constraint Bifurcation Theory dynamic aeroelasticity Nonlinear aeroelasticity

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Modeling and simulation of flexible flight vehicles

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JOURNAL OF GUIDANCE CONTROL AND dynamicS 2001年第3期24卷 539-546页

作者： Schmidt, DK Raney, DL Univ Colorado Flight Dynam & Control Lab Colorado Springs CO 80918 USA NASA Langley Res Ctr Dynam & Control Branch Hampton VA 23681 USA

The effects of flexibility on the flight dynamics of large aircraft have been shown to be quite significant, especial ly as the frequencies of the elastic modes become lower and approach those of the rigid-body modes. The handling characteristics of such vehicles are altered significantly from those of a rigid vehicle, and the design of the flight-control system may become drastically more complex. Consequently the need to model accurately the dynamics of such vehicles, and to develop valid simulations, is becoming particularly acute, The theoretical development of a generic flexible-aircraft model is reviewed. This modeling technique allows far the flexible degrees of freedom to be added to an existing simulation model of the vehicle's rigid-body dynamics. The data necessary for modeling a specific vehicle include aerodynamic stability derivatives, aerodynamic influence coefficients, elastic mode shapes, modal frequencies and damping, and generalized masses, Two case studies are presented, both involving the development of motion-based simulations in NASA Langley Research Center's simulation facility, The first example investigates an aircraft similar in geometry to the B-1, whereas the second investigates a large highspeed commercial transport, The dynamic responses (time and frequency domain) for these vehicles are presented, along with the evaluations of the effects of dynamic aeroelasticity on their handling characteristics. The vehicle responses are critical to evaluating hardware and software requirements for simulation fidelity, far example, visual and motion cues. Finally. a brief assessment of the effects of limitations of the simulation facility is presented, Limitations considered include digital time delay, motion hardware bandwidth, and motion washout logic.

关键词： Flight Vehicle NASA Langley Research Center dynamic aeroelasticity Power Spectral Density Aerodynamic Stability dynamic Response Rigid Body dynamics Test Pilots Elastic Deformation Fuselages

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Effect of Skin and Spar Laminate Orientations on Flutter of Composite UAV Wing

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JOURNAL OF AERONAUTICS ASTRONAUTICS AND AVIATION 2019年第2期51卷 201-211页

作者： Zaki, Nurul-Zubaidah Mazaha, Fareed A. Abdul-Latif, Ainullotfi Mansor, Shuhaimi Ab Wahid, Mastura Dahalan, Md. Nizam Othman, Norazila Mat, Shabudin B. Nasir, Mohd Nazri Mohd Univ Teknol Malaysia Aeronaut Lab Sch Mech Engn Fac Engn Utm Skudai 81310 Johor Malaysia

This paper presents an analytical study on the optimisation of composite laminate orientation lay-up to achieve the maximum flutter with minimum weight penalty. The study is carried out by using UTM CAMAR UAV swept back wing as a case study where the wing consists of two spars located at 35% and 55% of the wing chord length. The laminate lay-up of the spar and the wing skin are optimised by considering different variations of laminate ply orientation while the number of plies for each part are set to be constant throughout the work. The finite element analysis software, Abaqus, was used to obtain the structural natural frequencies for bending and torsion modes. The bending stiffness, torsion stiffness and the eigenvalues of the aeroelasticity equation of motion are computed using the mathematical software, MATLAB. The maximum flutter speed obtained from the study is 238.93 m/s with laminate configuration at [45 degrees/-45 degrees/45 degrees/-45 degrees] for wing skin, [45 degrees/-45 degrees/45 degrees] for forward spar, [45 degrees/-45 degrees] s for aft spar and [0 degrees/0 degrees/0 degrees/0 degrees] for the wing tip.

关键词： Flutter speed Composite wing dynamic aeroelasticity Composite laminates Fibre orientation

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