State-space representation of unsteady airfoil behavior

Leishman, J. Gordon; Nguyen, Kristy

doi:10.2514/3.25127

Cited by 176 publications

(94 citation statements)

References 9 publications

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“…1 A large contribution to the total aerodynamic loading is generated on the outer sections of the blades, which, in modern wind turbines, operate most of the time in attached flow conditions. Unsteady aerodynamic forces in attached flow are frequently described in the time domain using indicial formulations, as described by Beddoes [1] and Leishman [2]. Wind turbine simulation tools based on this approach include, among others, the aeroelastic code HAWC2 [3,4], Bladed [5], and FAST [6,7].…”

Section: Introductionmentioning

confidence: 99%

Indicial lift response function: an empirical relation for finite‐thickness airfoils, and effects on aeroelastic simulations

2012

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The aeroelastic response of wind turbines is often simulated in the time domain using indicial response techniques. Unsteady aerodynamics in attached flow are usually based on Jones's approximation of the flat plate indicial response, although the response for finite-thickness airfoils differs from the flat plate one.The indicial lift response of finite-thickness airfoils is simulated with a panel code, and an empirical relation is outlined connecting the airfoil indicial response to its geometric characteristics. The effects of different indicial approximations are evaluated on a 2D profile undergoing harmonic pitching motion in the attached flow region; the resulting lift forces are compared to Computational Fluid Dynamics (CFD) simulations. The relevance for aeroelastic simulations of a wind turbine is also evaluated, and the effects are quantified in terms of variations of equivalent fatigue loads, ultimate loads, and stability limits.The agreement with CFD computations of a 2D profile in harmonic motion is improved by the indicial function accounting for the finitethickness of the airfoil. Concerning the full wind turbine aeroelastic behavior, the differences between simulations based on Jones's and finitethickness indicial response functions are rather small; Jones's flat-plate approximation results in only slightly larger fatigue and ultimate loads, and lower stability limits.

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Section: Introductionmentioning

confidence: 99%

Indicial lift response function: an empirical relation for finite‐thickness airfoils, and effects on aeroelastic simulations

2012

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“…Assuming that the indicial functions are known, the aerodynamic forces and moments induced in any maneuver can be estimated by using the well-known Duhamel superposition integral [36]. Tobak et al [62,61] and Reisenthel et al [50,51] detailed the superposition process for the modeling of unsteady lift and pitch moment from angle of attack and pitch rate indicial functions.…”

Section: Indicial Functionsmentioning

confidence: 99%

Challenges in the aerodynamics modeling of an oscillating and translating airfoil at large incidence angles

Ghoreyshi

Cummings

2013

Aerospace Science and Technology

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The challenges in the modeling of the unsteady lift of a two-dimensional NACA 0012 airfoil oscillating and translating at large incidence angles are investigated in this paper. Forced oscillation motions with two reduced frequency values of 0.1 and 1.0 were used. The CFD results show that a hysteresis loop was developed in the lift variation with angle of attack; shapes of the loops change significantly with reduced frequency value. A dynamic stall vortex was identified in the pitching and plunging motions with k = 0.1.This vortex delays the onset of flow separation over the upper surface to a higher incidence than would occur in steady conditions. The unsteady lift of the very fast motion is enhanced significantly due to the formation of a compression wave on the lower surface and an expansion wave on the upper surface. The results show clear limitations of unsteady aerodynamic theories for modeling motions at high incidences. Also, the CFD solution of indicial functions show a large oscillation at angles of attack beyond the stall angle, but the predictions of a model based on Radial Basis Function matches CFD values quite well.

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“…where the coefficients are obtained by best-fitting the analytical reference curve for the specif- [19], an added aerodynamic state t y C , is introduced [71][72] which, due to linearity of the Laplace transform and its inverse [41], evolves from the initial rest condition 0 0 , y C and 0 0 , y C according to the linear ordinary differential equation (ODE):…”

Section: Added Aerodynamic Statesmentioning

confidence: 99%

Semi-Analytical Reduced-Order Models for the Aeroelastic Behavior of Subsonic Flexible Wings via Generalised Plate and Beam Formulations

Berci¹

2017

Proceedings of the 6th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COM

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State-space representation of unsteady airfoil behavior

Cited by 176 publications

References 9 publications

Indicial lift response function: an empirical relation for finite‐thickness airfoils, and effects on aeroelastic simulations

Indicial lift response function: an empirical relation for finite‐thickness airfoils, and effects on aeroelastic simulations

Challenges in the aerodynamics modeling of an oscillating and translating airfoil at large incidence angles

Semi-Analytical Reduced-Order Models for the Aeroelastic Behavior of Subsonic Flexible Wings via Generalised Plate and Beam Formulations

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