Investigation of flow at leading and trailing edges of pitching-up airfoil

Shih, Chiang; Lourenco, L.; Krothapalli, A.

doi:10.2514/3.12560

Cited by 44 publications

(26 citation statements)

References 18 publications

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“…Several other experimental investigations of dynamic stall were carried out since then, including particle image velocimetry measurements [8,9], culminating in a nearly complete visualization of the dynamic stall phenomenon [10].…”

Section: Introductionmentioning

confidence: 99%

Bifurcation Behavior of Airfoil Undergoing Stall Flutter Oscillations in Low-Speed Wind Tunnel

Dimitriadis

2009

AIAA Journal

114

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Stall flutter is a nonlinear aeroelastic phenomenon that can affect several types of aeroelastic systems such as helicopter rotor blades, wind turbine blades, and highly flexible wings. Although the related aerodynamic phenomenon of dynamic stall has been the subject of many experimental studies, stall flutter itself has rarely been investigated. This paper presents a set of experiments conducted on a NACA0012 airfoil undergoing stall flutter oscillations in a low-speed wind tunnel. The aeroelastic responses are analyzed with the objective of characterizing the local bifurcation behavior of the system. It is shown that symmetric stall flutter oscillations are encountered as a result of a subcritical Hopf bifurcation, followed by a fold bifurcation. The cause of these bifurcations is the occurrence of dynamic stall, which allows the transfer of energy from the freestream to the wing. A second bifurcation occurs at the system's static divergence airspeed. As a consequence, the wing starts to undergo asymmetric stall flutter bifurcations at only positive (or only negative) pitch angles. The dynamic stall mechanism itself does not change but the flow only separates on one side of the wing.

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Section: Introductionmentioning

confidence: 99%

Bifurcation Behavior of Airfoil Undergoing Stall Flutter Oscillations in Low-Speed Wind Tunnel

Dimitriadis

2009

AIAA Journal

114

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“…Koochesfahani (1989) conducted a series of LRN experiments and showed the strong dependence of the resulting wake structures and thrust coefficients of a pitching airfoil on frequency and amplitude of oscillation. In a similar study, the vortex-vortex interactions and their influence on the aerodynamic forces were explored by Shih et al (1995). Akbari and Price (2003) simulated the LRN flow field around a pitching airfoil utilizing N-S equations.…”

Section: Introductionmentioning

confidence: 99%

An investigation into the effects of unsteady parameters on the aerodynamics of a low Reynolds number pitching airfoil

Amiralaei

Alighanbari

Hashemi

2010

Journal of Fluids and Structures

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“…It was shown by Robinson et al 8 and Carr 5 that the ow away from the wing tip is nearly two-dimensional for a wing in pitch up. Shih et al 4 show that the unsteady separation that leads to the formation of the dynamic-stall vortex is a local ow phenomena restricted to the leading-edge region and that the trailing-edge ow does not have a direct impact on the leading-edge separation process. Therefore, realistic and useful data can be obtained from this type of analysis.…”

Section: Introductionmentioning

confidence: 98%

“…The resulting ow eld for an airfoil that experiences a rapid unsteady pitch up is quite different than an airfoil in a quasi-steady-statemotion. Shih et al 4 noted that this difference is primarily due to the interaction of local unsteady boundary-layer separation and the external ow, which eventually leads to massive boundary-layer separation and the formation of large-scale vortices. This type of dominant vortex is referred to as a dynamic-stallvortex.…”

Section: Introductionmentioning

confidence: 98%

Effects of Surface Ice Roughness on Dynamic Stall

Huebsch

Rothmayer

2002

Journal of Aircraft

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A two-dimensional Navier-Stokes algorithm is used to investigate unsteady, incompressible viscous ow past an airfoil leading edge with surface roughness that is characteristic of early-growth ice accretion. The roughness is added to the surface through the use of a Prandtl transposition and can generate both small-scale and large-scale roughness geometries. The algorithm is used to simulate steady or unsteady ow at constant angle of attack or pitch up corresponding to dynamic-stall conditions. Investigations of the dynamic stall show that some types of surface roughness can signi cantly alter the unsteady ow separation pattern and the formation of the dynamic-stall vortex. This includes both small-scale and large-scale roughness. Nomenclaturec = airfoil chord length f .» / = analytic expression for roughness geometry h = hump height K .t/ = angle-of-attack parameter l = leading-edge radius of curvature for parabola Re = Reynolds number P ® = pitch ratē = scale factor for governing equationś 0 ;´; Ń = normal coordinates » 0 ; »; N » = streamwise coordinates ¿ = pseudotime Ã; 9 = stream function !; Ä = vorticity Subscripts inv = inviscid value L ; R = left and right locations, respectively w = value at the wall 1 = freestream value

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Investigation of flow at leading and trailing edges of pitching-up airfoil

Cited by 44 publications

References 18 publications

Bifurcation Behavior of Airfoil Undergoing Stall Flutter Oscillations in Low-Speed Wind Tunnel

Bifurcation Behavior of Airfoil Undergoing Stall Flutter Oscillations in Low-Speed Wind Tunnel

An investigation into the effects of unsteady parameters on the aerodynamics of a low Reynolds number pitching airfoil

Effects of Surface Ice Roughness on Dynamic Stall

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