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G. Dimitriadis
Department of Aerospace and Mechanical Engineering, University of Liège, 4000 Liège, Belgium

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Journal article
Published: 11 April 2020 in Aerospace
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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.

ACS Style

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; Grigorios Dimitriadis. Effect of Levels of Fidelity on Steady Aerodynamic and Static Aeroelastic Computations. Aerospace 2020, 7, 42 .

AMA Style

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, Grigorios Dimitriadis. Effect of Levels of Fidelity on Steady Aerodynamic and Static Aeroelastic Computations. Aerospace. 2020; 7 (4):42.

Chicago/Turabian Style

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; Grigorios Dimitriadis. 2020. "Effect of Levels of Fidelity on Steady Aerodynamic and Static Aeroelastic Computations." Aerospace 7, no. 4: 42.

Proceedings article
Published: 06 January 2019 in AIAA Scitech 2019 Forum
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ACS Style

Thomas Lambert; Nicolas Warbecq; Patrick Hendrick; Robert Nudds; Thomas Andrianne; Grigorios Dimitriadis. Numerical and Experimental Investigation of Tandem Wing Flyers. AIAA Scitech 2019 Forum 2019, 1 .

AMA Style

Thomas Lambert, Nicolas Warbecq, Patrick Hendrick, Robert Nudds, Thomas Andrianne, Grigorios Dimitriadis. Numerical and Experimental Investigation of Tandem Wing Flyers. AIAA Scitech 2019 Forum. 2019; ():1.

Chicago/Turabian Style

Thomas Lambert; Nicolas Warbecq; Patrick Hendrick; Robert Nudds; Thomas Andrianne; Grigorios Dimitriadis. 2019. "Numerical and Experimental Investigation of Tandem Wing Flyers." AIAA Scitech 2019 Forum , no. : 1.

Journal article
Published: 07 December 2018 in Advances in Engineering Software
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CUPyDO, a fluid-structure interaction (FSI) tool that couples existing independent fluid and solid solvers into a single synchronization and communication framework based on the Python language is presented. Each coupled solver has to be wrapped in a Python layer in order to embed their functionalities (usually written in a compiled language) into a Python object, that is called and used by the coupler. Thus a staggered strong coupling can be achieved for time-dependent FSI problems such as aeroelastic flutter, vortex-induced vibrations (VIV) or conjugate heat transfer (CHT). The synchronization between the solvers is performed with the predictive block-Gauss-Seidel algorithm with dynamic under-relaxation. The tool is capable of treating non-matching meshes between the fluid and structure domains and is optimized to work in parallel using Message Passing Interface (MPI). The implementation of CUPyDO is described and its capabilities are demonstrated on typical validation cases. The open-source code SU2 is used to solve the fluid equations while the solid equations are solved either by a simple rigid body integrator or by in-house linear/nonlinear Finite Element codes (GetDP/Metafor). First, the modularity of the coupling as well as its ease of use is highlighted and then the accuracy of the results is demonstrated.

ACS Style

D. Thomas; M.L. Cerquaglia; R. Boman; T.D. Economon; J.J. Alonso; G. Dimitriadis; V.E. Terrapon. CUPyDO - An integrated Python environment for coupled fluid-structure simulations. Advances in Engineering Software 2018, 128, 69 -85.

AMA Style

D. Thomas, M.L. Cerquaglia, R. Boman, T.D. Economon, J.J. Alonso, G. Dimitriadis, V.E. Terrapon. CUPyDO - An integrated Python environment for coupled fluid-structure simulations. Advances in Engineering Software. 2018; 128 ():69-85.

Chicago/Turabian Style

D. Thomas; M.L. Cerquaglia; R. Boman; T.D. Economon; J.J. Alonso; G. Dimitriadis; V.E. Terrapon. 2018. "CUPyDO - An integrated Python environment for coupled fluid-structure simulations." Advances in Engineering Software 128, no. : 69-85.

Journal article
Published: 01 September 2018 in Aerospace
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A method is presented to model the incompressible, attached, unsteady lift and pitching moment acting on a thin three-dimensional wing in the time domain. The model is based on the combination of Wagner theory and lifting line theory through the unsteady Kutta–Joukowski theorem. The results are a set of closed-form linear ordinary differential equations that can be solved analytically or using a Runge–Kutta–Fehlberg algorithm. The method is validated against numerical predictions from an unsteady vortex lattice method for rectangular and tapered wings undergoing step or oscillatory changes in plunge or pitch. Further validation is demonstrated on an aeroelastic test case of a rigid rectangular finite wing with pitch and plunge degrees of freedom.

ACS Style

Johan Boutet; Grigorios Dimitriadis. Unsteady Lifting Line Theory Using the Wagner Function for the Aerodynamic and Aeroelastic Modeling of 3D Wings. Aerospace 2018, 5, 92 .

AMA Style

Johan Boutet, Grigorios Dimitriadis. Unsteady Lifting Line Theory Using the Wagner Function for the Aerodynamic and Aeroelastic Modeling of 3D Wings. Aerospace. 2018; 5 (3):92.

Chicago/Turabian Style

Johan Boutet; Grigorios Dimitriadis. 2018. "Unsteady Lifting Line Theory Using the Wagner Function for the Aerodynamic and Aeroelastic Modeling of 3D Wings." Aerospace 5, no. 3: 92.

Journal article
Published: 10 May 2018 in Journal of Fluids and Structures
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The majority of methods for calculating the dynamic response of nonlinear aeroelastic systems considers only steady-state periodic behaviour. An exception is the Multiple Time Scales method, which can estimate both the transient and steady-state solutions of such systems; nevertheless, this approach is only accurate close to the Hopf bifurcation. This paper proposes a novel combined approach whereby the transient response is obtained from the Multiple Time Scales method and the asymptotic periodic behaviour is corrected using the Harmonic Balance method. This consistent and efficient framework mutually empowers both techniques and accounts for large parameter variations around the critical condition. The effect of cubic aero-structural nonlinearities on the dynamic response of a generic aeroelastic system is then investigated. Both the Multiple Time Scales and Harmonic Balance methods are adopted and perfect agreement of the explicit results is demonstrated, albeit near the system instability. In contrast, the proposed combined solution is valid for a wider range of perturbations, is analytical and has negligible computational cost while retaining accuracy. The role of key parameters and terms on the core mechanism of the dynamic behaviour is rigorously identified and discussed, from both physical and mathematical points of view. Galloping is finally considered as the simplest but complete application to a fundamental yet practical problem, featuring full conceptual complexity while exploiting the solid synthesis capability of the newly proposed analytical approach. Excellent agreement was found in all cases with results from the numerical integration of the nonlinear equations of motion in the time domain.

ACS Style

M. Berci; G. Dimitriadis. A combined Multiple Time Scales and Harmonic Balance approach for the transient and steady-state response of nonlinear aeroelastic systems. Journal of Fluids and Structures 2018, 80, 132 -144.

AMA Style

M. Berci, G. Dimitriadis. A combined Multiple Time Scales and Harmonic Balance approach for the transient and steady-state response of nonlinear aeroelastic systems. Journal of Fluids and Structures. 2018; 80 ():132-144.

Chicago/Turabian Style

M. Berci; G. Dimitriadis. 2018. "A combined Multiple Time Scales and Harmonic Balance approach for the transient and steady-state response of nonlinear aeroelastic systems." Journal of Fluids and Structures 80, no. : 132-144.

Journal article
Published: 01 July 2017 in Journal of Wind Engineering and Industrial Aerodynamics
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ACS Style

Chandra Shekhar Prasad; Grigorios Dimitriadis. Application of a 3D unsteady surface panel method with flow separation model to horizontal axis wind turbines. Journal of Wind Engineering and Industrial Aerodynamics 2017, 166, 74 -89.

AMA Style

Chandra Shekhar Prasad, Grigorios Dimitriadis. Application of a 3D unsteady surface panel method with flow separation model to horizontal axis wind turbines. Journal of Wind Engineering and Industrial Aerodynamics. 2017; 166 ():74-89.

Chicago/Turabian Style

Chandra Shekhar Prasad; Grigorios Dimitriadis. 2017. "Application of a 3D unsteady surface panel method with flow separation model to horizontal axis wind turbines." Journal of Wind Engineering and Industrial Aerodynamics 166, no. : 74-89.

Conference paper
Published: 26 June 2017 in Volume 2A: Turbomachinery
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This paper presents the results from a research effort on eigenvalue identification of mistuned bladed rotor systems using the Least-Squares Complex Frequency-Domain (LSCF) modal parameter estimator. The LSCF models the frequency response function (FRF) obtained from a vibration test using a matrix-fraction description and obtains the coefficients of the common denominator polynomial by minimizing the least squares error of the fit between the FRF and the model. System frequency and damping information is obtained from the roots of the denominator; a stabilization diagram is used to separate physical from mathematical poles. The LSCF estimator is known for its good performance when separating closely spaced modes, but few quantitative analyses have focused on the sensitivity of the identification with respect to mode concentration. In this study, the LSCF estimator is applied on both computational and experimental forced responses of an embedded compressor rotor in a three-stage axial research compressor. The LSCF estimator is first applied to computational FRF data obtained from a mistuned first-torsion (1T) forced response prediction using FMM (Fundamental Mistuning Model) and is shown to be able to identify the eigenvalues with high accuracy. Then the first chordwise bending (1CWB) computational FRF data is considered with varied mode concentration by varying the mistuning standard deviation. These cases are analyzed using LSCF and a sensitivity algorithm is developed to evaluate the influence of the mode spacing on eigenvalue identification. Finally, the experimental FRF data from this rotor blisk is analyzed using the LSCF estimator. For the dominant modes, the identified frequency and damping values compare well with the computational values.

ACS Style

Yuan Huang; Grigorios Dimitriadis; Robert E. Kielb; Jing Li. System Eigenvalue Identification of Mistuned Bladed Disks Using Least-Squares Complex Frequency-Domain Method. Volume 2A: Turbomachinery 2017, 1 .

AMA Style

Yuan Huang, Grigorios Dimitriadis, Robert E. Kielb, Jing Li. System Eigenvalue Identification of Mistuned Bladed Disks Using Least-Squares Complex Frequency-Domain Method. Volume 2A: Turbomachinery. 2017; ():1.

Chicago/Turabian Style

Yuan Huang; Grigorios Dimitriadis; Robert E. Kielb; Jing Li. 2017. "System Eigenvalue Identification of Mistuned Bladed Disks Using Least-Squares Complex Frequency-Domain Method." Volume 2A: Turbomachinery , no. : 1.

Journal article
Published: 01 May 2017 in AIAA Journal
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The current drive for increased efficiency in aeronautic structures such as aircraft, wind-turbine blades, and helicopter blades often leads to weight reduction. A consequence of this tendency can be increased flexibility, which in turn can lead to unfavorable aeroelastic phenomena involving large-amplitude oscillations and nonlinear effects such as geometric hardening and stall flutter. Vibration mitigation is one of the approaches currently under study for avoiding these phenomena. In the present work, passive vibration mitigation is applied to a nonlinear experimental aeroelastic system by means of a linear tuned vibration absorber. The aeroelastic apparatus is a pitch and flap wing that features a continuously hardening restoring torque in pitch and a linear restoring torque in flap. Extensive analysis of the system with and without absorber at precritical and postcritical airspeeds showed an improvement in flutter speed of around 36%, a suppression of a jump due to stall flutter, and a reduction in limit-cycle oscillation amplitude. Mathematical modeling of the experimental system is used to demonstrate that optimal flutter delay is achieved when two of the system modes flutter at the same flight condition. Nevertheless, even this optimal absorber quickly loses effectiveness as it is detuned. The wind-tunnel measurements showed that the tested absorbers were much slower to lose effectiveness than those of the mathematical predictions.

ACS Style

Edouard Verstraelen; Giuseppe Habib; Gaetan Kerschen; Grigorios Dimitriadis. Experimental Passive Flutter Suppression Using a Linear Tuned Vibration Absorber. AIAA Journal 2017, 55, 1 -16.

AMA Style

Edouard Verstraelen, Giuseppe Habib, Gaetan Kerschen, Grigorios Dimitriadis. Experimental Passive Flutter Suppression Using a Linear Tuned Vibration Absorber. AIAA Journal. 2017; 55 (5):1-16.

Chicago/Turabian Style

Edouard Verstraelen; Giuseppe Habib; Gaetan Kerschen; Grigorios Dimitriadis. 2017. "Experimental Passive Flutter Suppression Using a Linear Tuned Vibration Absorber." AIAA Journal 55, no. 5: 1-16.

Journal article
Published: 18 April 2017 in Aerospace
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Flapping flight is an increasingly popular area of research, with applications to micro-unmanned air vehicles and animal flight biomechanics. Fast, but accurate methods for predicting the aerodynamic loads acting on flapping wings are of interest for designing such aircraft and optimizing thrust production. In this work, the unsteady vortex lattice method is used in conjunction with three load estimation techniques in order to predict the aerodynamic lift and drag time histories produced by flapping rectangular wings. The load estimation approaches are the Katz, Joukowski and simplified Leishman–Beddoes techniques. The simulations’ predictions are compared to experimental measurements from wind tunnel tests of a flapping and pitching wing. Three types of kinematics are investigated, pitch-leading, pure flapping and pitch lagging. It is found that pitch-leading tests can be simulated quite accurately using either the Katz or Joukowski approaches as no measurable flow separation occurs. For the pure flapping tests, the Katz and Joukowski techniques are accurate as long as the static pitch angle is greater than zero. For zero or negative static pitch angles, these methods underestimate the amplitude of the drag. The Leishman–Beddoes approach yields better drag amplitudes, but can introduce a constant negative drag offset. Finally, for the pitch-lagging tests the Leishman–Beddoes technique is again more representative of the experimental results, as long as flow separation is not too extensive. Considering the complexity of the phenomena involved, in the vast majority of cases, the lift time history is predicted with reasonable accuracy. The drag (or thrust) time history is more challenging.

ACS Style

Thomas Lambert; Norizham Abdul Razak; Grigorios Dimitriadis. Vortex Lattice Simulations of Attached and Separated Flows around Flapping Wings. Aerospace 2017, 4, 22 .

AMA Style

Thomas Lambert, Norizham Abdul Razak, Grigorios Dimitriadis. Vortex Lattice Simulations of Attached and Separated Flows around Flapping Wings. Aerospace. 2017; 4 (2):22.

Chicago/Turabian Style

Thomas Lambert; Norizham Abdul Razak; Grigorios Dimitriadis. 2017. "Vortex Lattice Simulations of Attached and Separated Flows around Flapping Wings." Aerospace 4, no. 2: 22.

Journal article
Published: 01 February 2017 in Journal of Fluids and Structures
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Freeplay is a significant source of nonlinearity in aeroelastic systems and is strictly regulated by airworthiness authorities. It splits the phase plane of such systems into three piecewise linear subdomains. Depending on the location of the freeplay, limit cycle oscillations can result that span either two or three of these subdomains. The purpose of this work is to demonstrate the existence of two-domain cycles both theoretically and experimentally. A simple aeroelastic system with pitch, plunge and control deflection degrees of freedom is investigated in the presence of freeplay in pitch. It is shown that two-domain and three-domain cycles can result from a grazing bifurcation and propagate in the decreasing airspeed direction. Close to the bifurcation, the two limit cycle branches interact with each other and aperiodic oscillations ensue. Equivalent linearization is used to derive the conditions of existence of each type of limit cycle and to predict their amplitudes and frequencies. Comparisons with measurements from wind tunnel experiments demonstrate that the theory describes these phenomena with accuracy.Comment: 26 pages, 16 figure

ACS Style

Edouard Verstraelen; Grigorios Dimitriadis; Gustavo Dal Ben Rossetto; Earl Dowell. Two-domain and three-domain limit cycles in a typical aeroelastic system with freeplay in pitch. Journal of Fluids and Structures 2017, 69, 89 -107.

AMA Style

Edouard Verstraelen, Grigorios Dimitriadis, Gustavo Dal Ben Rossetto, Earl Dowell. Two-domain and three-domain limit cycles in a typical aeroelastic system with freeplay in pitch. Journal of Fluids and Structures. 2017; 69 ():89-107.

Chicago/Turabian Style

Edouard Verstraelen; Grigorios Dimitriadis; Gustavo Dal Ben Rossetto; Earl Dowell. 2017. "Two-domain and three-domain limit cycles in a typical aeroelastic system with freeplay in pitch." Journal of Fluids and Structures 69, no. : 89-107.

Brief report
Published: 01 February 2017 in AIAA Journal
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The Unsteady Vortex Lattice Method (UVLM) is an approach widely used to estimate the aerodynamic loads in unsteady subsonic flows. It is based on modeling the camber surface of a lifting body by means of bound vortex rings. Even though this method has been known and used for several decades, there is little discussion of the modeling of the leading-edge suction in the literature. To address this concern, Simpson et al. [1] presented a comparison of two different ways to model this effect for the case of uncambered airfoils and wings in harmonic pitch or plunge motions. They concluded that the Joukowski method converges significantly faster than the Katz technique as the number of chorwise panels is increased. The present paper is an extension of the study by Simpson et al. to cambered lifting surfaces. It shows that the presence of camber can change radically the convergence performance of the two methods. For cambered wings, the Katz approach converges significantly faster than the Joukowski technique.Peer reviewe

ACS Style

Thomas Lambert; Grigorios Dimitriadis. Induced Drag Calculations with the Unsteady Vortex Lattice Method for Cambered Wings. AIAA Journal 2017, 55, 668 -672.

AMA Style

Thomas Lambert, Grigorios Dimitriadis. Induced Drag Calculations with the Unsteady Vortex Lattice Method for Cambered Wings. AIAA Journal. 2017; 55 (2):668-672.

Chicago/Turabian Style

Thomas Lambert; Grigorios Dimitriadis. 2017. "Induced Drag Calculations with the Unsteady Vortex Lattice Method for Cambered Wings." AIAA Journal 55, no. 2: 668-672.

Conference paper
Published: 05 January 2017 in 55th AIAA Aerospace Sciences Meeting
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A method is presented to model the incompressible, attached, unsteady lift and moment acting on a thin three-dimensional wing in the time domain. The model is based on the combination of Wagner theory and lifting line theory trough the unsteady Kutta-Joukowsky theorem. The result is a set of closed form linear ordinary di erential equations that can be solved analytically or using a Runge-Kutta-Fehlberg algorithm. The method is validated against numerical predictions from an unsteady Vortex Lattice method for rectangular and tapered wings undergoing step or oscillatory changes in plunge or pitch. As the aerodynamic loads are written in state space form in the proposed method, they can be easily included in aeroelastic and flight dynamic calculations

ACS Style

Johan Boutet; Grigorios Dimitriadis. Time domain analytical unsteady aerodynamic modelling for finite wings. 55th AIAA Aerospace Sciences Meeting 2017, 1 .

AMA Style

Johan Boutet, Grigorios Dimitriadis. Time domain analytical unsteady aerodynamic modelling for finite wings. 55th AIAA Aerospace Sciences Meeting. 2017; ():1.

Chicago/Turabian Style

Johan Boutet; Grigorios Dimitriadis. 2017. "Time domain analytical unsteady aerodynamic modelling for finite wings." 55th AIAA Aerospace Sciences Meeting , no. : 1.

Research article
Published: 19 November 2016 in Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy
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This paper describes the development of a complete methodology for the aeroservoelastic modelling of horizontal axis wind turbines at the conceptual design stage. The methodology is based on the implementation of unsteady aerodynamic modelling, advanced description of the control system and nonlinear finite element calculations in the Samcef Wind Turbines design package. The aerodynamic modelling is carried out by means of fast techniques, such as the blade element method and the unsteady vortex lattice method, including a free wake model. The complete model also includes a description of a doubly fed induction generator and its control system for variable speed operation. The Samcef Wind Turbines software features a nonlinear finite element solver with multi-body dynamics capability. The full methodology is used to perform complete aeroservoelastic simulations of a realistic 2 MW wind turbine model. The interaction between the three components of the approach is carefully analysed and presented here.

ACS Style

Chandra Shekhar Prasad; Qiong Zhong Chen; Olivier Bruls; Flavio D'ambrosio; Grigorios Dimitriadis. Aeroservoelastic simulations for horizontal axis wind turbines. Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 2016, 231, 103 -117.

AMA Style

Chandra Shekhar Prasad, Qiong Zhong Chen, Olivier Bruls, Flavio D'ambrosio, Grigorios Dimitriadis. Aeroservoelastic simulations for horizontal axis wind turbines. Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy. 2016; 231 (2):103-117.

Chicago/Turabian Style

Chandra Shekhar Prasad; Qiong Zhong Chen; Olivier Bruls; Flavio D'ambrosio; Grigorios Dimitriadis. 2016. "Aeroservoelastic simulations for horizontal axis wind turbines." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 231, no. 2: 103-117.

Journal article
Published: 20 October 2016 in PeerJ
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The diversity of wing morphologies in birds reflects their variety of flight styles and the associated aerodynamic and inertial requirements. Although the aerodynamics underlying wing morphology can be informed by aeronautical research, important differences exist between planes and birds. In particular, birds operate at lower, transitional Reynolds numbers than do most aircraft. To date, few quantitative studies have investigated the aerodynamic performance of avian wings as fixed lifting surfaces and none have focused upon the differences between wings from different flight style groups. Dried wings from 10 bird species representing three distinct flight style groups were mounted on a force/torque sensor within a wind tunnel in order to test the hypothesis that wing morphologies associated with different flight styles exhibit different aerodynamic properties. Morphological differences manifested primarily as differences in drag rather than lift. Maximum lift coefficients did not differ between groups, whereas minimum drag coefficients were lowest in undulating flyers (Corvids). The lift to drag ratios were lower than in conventional aerofoils and data from free-flying soaring species; particularly in high frequency, flapping flyers (Anseriformes), which do not rely heavily on glide performance. The results illustrate important aerodynamic differences between the wings of different flight style groups that cannot be explained solely by simple wing-shape measures. Taken at face value, the results also suggest that wing-shape is linked principally to changes in aerodynamic drag, but, of course, it is aerodynamics during flapping and not gliding that is likely to be the primary driver.

ACS Style

John J. Lees; Grigorios Dimitriadis; Robert L. Nudds. The influence of flight style on the aerodynamic properties of avian wings as fixed lifting surfaces. PeerJ 2016, 4, e2495 .

AMA Style

John J. Lees, Grigorios Dimitriadis, Robert L. Nudds. The influence of flight style on the aerodynamic properties of avian wings as fixed lifting surfaces. PeerJ. 2016; 4 ():e2495.

Chicago/Turabian Style

John J. Lees; Grigorios Dimitriadis; Robert L. Nudds. 2016. "The influence of flight style on the aerodynamic properties of avian wings as fixed lifting surfaces." PeerJ 4, no. : e2495.

Book chapter
Published: 23 April 2016 in Conference Proceedings of the Society for Experimental Mechanics Series
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The current drive for increased efficiency in aeronautic structures such as aircraft, wind turbine blades and helicopter blades often leads to weight reduction. A consequence of this tendency can be increased flexibility, which in turn can lead to unfavourable aeroelastic phenomena involving large amplitude oscillations and nonlinear effects such as geometric hardening and stall flutter. Vibration mitigation is one of the approaches currently under study for avoiding these phenomena. In the present work, passive vibration mitigation is applied to an experimental aeroelastic system by means of a linear tuned vibration absorber. The aeroelastic apparatus is a pitch and flap wing that features a continuously hardening restoring torque in pitch and a linear one in flap. Extensive analysis of the system with and without absorber at subcritical and supercritical airspeeds showed an improvement in flutter speed around 34 %, a suppression of a jump due to stall flutter, and a reduction in LCO amplitude. Mathematical modelling of the experimental system showed that optimal flutter delay can be obtained when two of the system modes flutter simultaneously. However, the absorber quickly loses effectiveness as it is detuned. The wind tunnel measurements showed that the tested absorbers were much slower to lose effectiveness than those of the mathematical predictions.

ACS Style

E. Verstraelen; Giuseppe Habib; G. Kerschen; Grigorios Dimitriadis. Experimental Passive Flutter Mitigation Using a Linear Tuned Vibrations Absorber. Conference Proceedings of the Society for Experimental Mechanics Series 2016, 389 -403.

AMA Style

E. Verstraelen, Giuseppe Habib, G. Kerschen, Grigorios Dimitriadis. Experimental Passive Flutter Mitigation Using a Linear Tuned Vibrations Absorber. Conference Proceedings of the Society for Experimental Mechanics Series. 2016; ():389-403.

Chicago/Turabian Style

E. Verstraelen; Giuseppe Habib; G. Kerschen; Grigorios Dimitriadis. 2016. "Experimental Passive Flutter Mitigation Using a Linear Tuned Vibrations Absorber." Conference Proceedings of the Society for Experimental Mechanics Series , no. : 389-403.

Conference paper
Published: 01 January 2016 in Proceedings of the VII European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS Congress 2016)
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ACS Style

Ruben Sanchez; Heather L. Kline; David Thomas; Anil Variyar; Marcello Righi; Thomas D. Economon; Juan J. Alonso; Rafael Palacios; Grigorios Dimitriadis; Vincent Terrapon. ASSESSMENT OF THE FLUID-STRUCTURE INTERACTION CAPABILITIES FOR AERONAUTICAL APPLICATIONS OF THE OPEN-SOURCE SOLVER SU2. Proceedings of the VII European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS Congress 2016) 2016, 1 .

AMA Style

Ruben Sanchez, Heather L. Kline, David Thomas, Anil Variyar, Marcello Righi, Thomas D. Economon, Juan J. Alonso, Rafael Palacios, Grigorios Dimitriadis, Vincent Terrapon. ASSESSMENT OF THE FLUID-STRUCTURE INTERACTION CAPABILITIES FOR AERONAUTICAL APPLICATIONS OF THE OPEN-SOURCE SOLVER SU2. Proceedings of the VII European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS Congress 2016). 2016; ():1.

Chicago/Turabian Style

Ruben Sanchez; Heather L. Kline; David Thomas; Anil Variyar; Marcello Righi; Thomas D. Economon; Juan J. Alonso; Rafael Palacios; Grigorios Dimitriadis; Vincent Terrapon. 2016. "ASSESSMENT OF THE FLUID-STRUCTURE INTERACTION CAPABILITIES FOR AERONAUTICAL APPLICATIONS OF THE OPEN-SOURCE SOLVER SU2." Proceedings of the VII European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS Congress 2016) , no. : 1.

Book chapter
Published: 01 January 2016 in Conference Proceedings of the Society for Experimental Mechanics Series
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Nonlinear aeroelastic phenomena such as store-induced LCOs, transonic buzz and stall flutter are the burden or modern aircraft: they reduce the performance and can even limit the flight envelope in both civil and military cases. Several nonlinear setups were studied experimentally in the last decades by the scientific community but most of them have pitch and plunge degrees of freedom and feature a rigid wing. In this paper, we study a new nonlinear aeroelastic apparatus that features nonlinear pitch and flap degrees of freedom, coupled with a flexible wing. The model is tested experimentally in the wind tunnel to determine its dynamic behaviour. Preliminary observations demonstrate that the system undergoes a supercritical Hopf bifurcation due to the hardening nonlinearity followed by an amplitude jump that is the consequence of either dynamic stall (i.e. stall flutter) or internal resonance (i.e. interaction between the hardening nonlinearity and higher modes).

ACS Style

E. Verstraelen; G. Kerschen; G. Dimitriadis. Internal Resonance and Stall Flutter Interactions in a Pitch-Flap Wing in the Wind-Tunnel. Conference Proceedings of the Society for Experimental Mechanics Series 2016, 521 -531.

AMA Style

E. Verstraelen, G. Kerschen, G. Dimitriadis. Internal Resonance and Stall Flutter Interactions in a Pitch-Flap Wing in the Wind-Tunnel. Conference Proceedings of the Society for Experimental Mechanics Series. 2016; ():521-531.

Chicago/Turabian Style

E. Verstraelen; G. Kerschen; G. Dimitriadis. 2016. "Internal Resonance and Stall Flutter Interactions in a Pitch-Flap Wing in the Wind-Tunnel." Conference Proceedings of the Society for Experimental Mechanics Series , no. : 521-531.

Journal article
Published: 01 July 2015 in Journal of Aircraft
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Freeplay in aircraft control-surface actuators is a common source of nonlinearity that can cause undesirable aeroelastic phenomena, and as a consequence, certification authorities place strict limits on the size of the deadband gaps of actuators. In recent years, many authors have worked on determining the effects of freeplay on the dynamic behavior of aeroelastic systems; these efforts have yielded significant improvements in the understanding of the phenomena but have concentrated on simple models. Investigations of industry-relevant aeroelastic models of complete aircraft with freeplay in the actuators have been much rarer, with the main difficulty being the selection of an appropriate modal basis that can represent the full range of possible dynamic phenomena. This work presents a novel implementation of the residual vectors approach to create consistent and numerically stable reduced-order models suitable for industrial-standard aeroelastic models of aircraft. The methodology relies on the piecewise linear nature of freeplay to create a single reduction basis that represents the dynamics of the system both inside and outside the freeplay deadband gap. The method is demonstrated on an Embraer generic test-bench aircraft, showing that the resulting reduced-order model is efficient and effective. Nonlinear analysis is carried out using equivalent linearization as well as time integrations of the full nonlinear system. It is shown that, although equivalent linearization is an indispensable tool for a preliminary mapping of the main aeroelastic instabilities, the time-integration-based nonlinear analysis is an essential complementary tool to confirm the characteristics of the system behavior.

ACS Style

Gustavo H. C. Silva; Gustavo Dal Ben Rossetto; Grigorios Dimitriadis. Reduced-Order Analysis of Aeroelastic Systems with Freeplay Using an Augmented Modal Basis. Journal of Aircraft 2015, 52, 1312 -1325.

AMA Style

Gustavo H. C. Silva, Gustavo Dal Ben Rossetto, Grigorios Dimitriadis. Reduced-Order Analysis of Aeroelastic Systems with Freeplay Using an Augmented Modal Basis. Journal of Aircraft. 2015; 52 (4):1312-1325.

Chicago/Turabian Style

Gustavo H. C. Silva; Gustavo Dal Ben Rossetto; Grigorios Dimitriadis. 2015. "Reduced-Order Analysis of Aeroelastic Systems with Freeplay Using an Augmented Modal Basis." Journal of Aircraft 52, no. 4: 1312-1325.

Journal article
Published: 01 July 2015 in The Aeronautical Journal
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The flight of barnacle geese at airspeeds representing high-speed migrating flight is investigated using experiments and simulations. The experimental part of the work involved the filming of three barnacle geese (Branta Leucopsis) flying at different airspeeds in a wind tunnel. The video footage was analysed in order to extract the wing kinematics. Additional information, such as wing geometry and camber was obtained from a 3D scan of a dried wing. An unsteady vortex lattice method was used to simulate the aerodynamics of the measured flapping motion. The simulations were used in order to successfully reproduce the measured body motion and thus obtain estimates of the aerodynamic forces acting on the wings. It was found that the mean of the wing pitch angle variation with time has the most significant effect on lift while the difference in the durations of the upstroke and downstroke has the major effect on thrust. The power consumed by the aerodynamic forces was also estimated; it was found that increases in aerodynamic power correspond very closely to climbing motion and vice versa. Root-mean-square values of the power range from 100W to 240W. Finally, it was observed that tandem flying can be very expensive for the trailing bird.

ACS Style

G. Dimitriadis; J. D. Gardiner; Peter Tickle; Jonathan Codd; R. L. Nudds. Experimental and numerical study of the flight of geese. The Aeronautical Journal 2015, 119, 803 -832.

AMA Style

G. Dimitriadis, J. D. Gardiner, Peter Tickle, Jonathan Codd, R. L. Nudds. Experimental and numerical study of the flight of geese. The Aeronautical Journal. 2015; 119 (1217):803-832.

Chicago/Turabian Style

G. Dimitriadis; J. D. Gardiner; Peter Tickle; Jonathan Codd; R. L. Nudds. 2015. "Experimental and numerical study of the flight of geese." The Aeronautical Journal 119, no. 1217: 803-832.

Correction
Published: 12 May 2015 in PLoS ONE
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ACS Style

Dieter VanderElst; Herbert Peremans; Norizham Abdul Razak; Edouard Verstraelen; Grigorios Dimitriadis. Correction: The Aerodynamic Cost of Head Morphology in Bats: Maybe Not as Bad as It Seems. PLoS ONE 2015, 10, e0126061 -e0126061.

AMA Style

Dieter VanderElst, Herbert Peremans, Norizham Abdul Razak, Edouard Verstraelen, Grigorios Dimitriadis. Correction: The Aerodynamic Cost of Head Morphology in Bats: Maybe Not as Bad as It Seems. PLoS ONE. 2015; 10 (5):e0126061-e0126061.

Chicago/Turabian Style

Dieter VanderElst; Herbert Peremans; Norizham Abdul Razak; Edouard Verstraelen; Grigorios Dimitriadis. 2015. "Correction: The Aerodynamic Cost of Head Morphology in Bats: Maybe Not as Bad as It Seems." PLoS ONE 10, no. 5: e0126061-e0126061.