A state-space model of unsteady aerodynamics in a compressible flow for flutter analyses

Leishman, J. Gordon; Crouse, Gilbert L.

doi:10.2514/6.1989-22

Cited by 19 publications

(9 citation statements)

References 1 publication

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“…65,66,67,68,69,70,71,72 The above discussion presumes linear dependence of the lift on α, U α, or U sin α. Within the framework of potential flow, the lift is linearly dependent on the circulation.…”

Section: Extension Of Duhamel Principle To Arbitrary Nonlinear C mentioning

confidence: 98%

Unsteady Nonlinear Aerodynamics of Hovering MAVs/Insects

Taha

Hajj

Beran³

2013

51st AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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The Duhamel superposition principle, applied in unsteady linear aerodynamics, is extended to arbitrary nonlinear lift curves. The unsteady lift due to arbitrary wing motion is generated using the static nonlinear lift curve. A finite-state unsteady aerodynamic model that is based on a two-state approximation of Wagner function is developed. As such, it is suitable for dynamic stability analysis and control synthesis for the systems experiencing nonlinear unsteady flows such as wind turbine blades, rapidly maneuvering aircraft, highly flexible wings, and micro-air-vehicles. The proposed unsteady model is applied to flapping flight and validated through a comparison with direct numerical simulations of Navier-Stokes on hovering insects.

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Section: Extension Of Duhamel Principle To Arbitrary Nonlinear C mentioning

confidence: 98%

Unsteady Nonlinear Aerodynamics of Hovering MAVs/Insects

Taha

Hajj

Beran³

2013

51st AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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“…14, and its subsequent improvement in the present research, was the mathematically-correct definition of the input to an unsteady aerodynamic system for the discrete-time domain. The input function consists of the downwash function, which, for the excitation of a given mode is written as w(x,y,t) = phiÕ(x,y)¥u(t) + phi(x,y)¥uÕ(t) (4) where phi(x,y) is the modeshape, phiÕ(x,y) are the slopes of the modeshape, u(t) is the generalized coordinate, and uÕ(t) is the derivative of the generalized coordinate. The discussion will be limited, temporarily, to the linear case.…”

Section: Aerodynamic System Input Definitionmentioning

confidence: 99%

“…Attempts to address this problem include the development of transonic indicial responses 3,4,5 . Reference 6 develops models of nonlinear aerodynamic maneuvers from an experimental database using neural networks.…”

Section: Introductionmentioning

confidence: 99%

Identification of linear and nonlinear aerodynamic impulse responses using digital filter techniques

Silva

1997

22nd Atmospheric Flight Mechanics Conference

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“…Ocokoljić, et al investigated the requirements for the accuracy of measurements in a wind tunnel, such as calibration of the wind tunnel test section [12]. Other relevant studies have also focused on stall-induced vibration analysis [13,14], bifurcation and chaos analysis [15][16][17], non-linear dynamics [18], and stability analysis [19]. It could be concluded that one of the main objectives of all studies in this field is to develop a reliable, precise, and fast method for aero-elastic behavior, stability, and the flutter speed analysis while avoiding numerical integration issues of instability and inaccuracy.…”

Section: Introductionmentioning

confidence: 99%

Control Surface Freeplay Effects Investigation on Airfoil’s Aero-Elastic Behavior in the Sub-Sonic Regime

2019

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One of the main limitations of linearity assumptions in airfoil’s aero-elastic problems is the inability to predict the system behavior after starting the instability. In reality, nonlinearities may prevent the amplitudes from going to infinity. This paper presents a methodological approach for predicting airfoil aero-elastic behavior to investigate the control surface freeplay effects on the state responses and the flutter speed. For this purpose, the airfoil structural model is firstly developed while using the Lagrange’s method. The aerodynamic model is then generated by utilizing the Theodorsen approach for lift and moment calculation and Jones approximation with P-method for unstable aerodynamic modelling. After that, the aero-elastic model is developed by combination of structural and aerodynamic models and a numerical integration method is used to extract the time responses in the state space. The flutter analysis has been completed by utilizing the P-method for the system without freeplay and by the time response approach for the system with freeplay. The results that were obtained from simulations confirm the effectiveness of the proposed method to predict the aero-elastic behavior and stability condition of a two-dimensional airfoil as well as to estimate the flutter speed with reasonable accuracy and low computational effort. Moreover, a sensitivity analysis of freeplay degree on time response results has been done and the results are discussed in detail. It is also showed that the control surface freeplay decreases the flutter speed. The results of the paper are also validated against publicly available data.

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A state-space model of unsteady aerodynamics in a compressible flow for flutter analyses

Cited by 19 publications

References 1 publication

Unsteady Nonlinear Aerodynamics of Hovering MAVs/Insects

Unsteady Nonlinear Aerodynamics of Hovering MAVs/Insects

Identification of linear and nonlinear aerodynamic impulse responses using digital filter techniques

Control Surface Freeplay Effects Investigation on Airfoil’s Aero-Elastic Behavior in the Sub-Sonic Regime

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