Some aspects of aircraft dynamic loads due to flow separation

Mabey, D. G.

doi:10.1016/0376-0421(89)90006-7

Cited by 50 publications

(26 citation statements)

References 9 publications

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“…Flow separation leads to unsteady forcing on airfoils, a phenomenon known as buffeting [23]. This forcing can exist over a wide frequency band (i.e., aperiodic) or a narrow frequency band in the presence of vortex shedding (i.e., periodic).…”

Section: Introductionmentioning

confidence: 99%

Unsteady airloads on static airfoils through high angles of attack and in reverse flow

Lind

Jones

2016

Journal of Fluids and Structures

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The present work is aimed at understanding the sources, magnitude, and frequency of unsteady airloads acting on airfoils at high angles of attack and in reverse flow in order to improve the design of rotor blades for high-speed helicopters and wind turbines. Four rotor blade airfoils were tested at angles of attack through 180 • and at three Reynolds numbers, up to one million. The unsteady airloads acting on each airfoil were calculated by integrating time-resolved pressure measurements acquired along the midspan of the airfoil. Unsteady velocity fields for a NACA 0012 were calculated from time-resolved particle image velocimetry measurements. For all airfoils, the unsteady airloads were found to be large in magnitude near stall, when an unstable shear layer induces unsteady flow on the suction side of the airfoil. At post-stall angles of attack, the unsteady airloads generally decreased as a region of separated flow builds over the suction side. As the angle of attack was increased further, the airloads become periodic and the flow entered the deep stall vortex shedding regime. At high angles of attack (30 • ≤ α ≤ 150 • ), the unsteady airloads were greatest for airfoils with a blunt aerodynamic trailing edge due to unsteady induced flow from trailing edge vortices.Aerodynamic hysteresis was shown to cause large unsteady airloads as the static angle of attack is decreased near stall. The unsteady airloads of a NACA 0012 in reverse flow were observed to be insensitive to Reynolds number due to flow separation at the sharp leading edge of this relatively thin airfoil.

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Section: Introductionmentioning

confidence: 99%

Unsteady airloads on static airfoils through high angles of attack and in reverse flow

Lind

Jones

2016

Journal of Fluids and Structures

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“…Instead, it is more convenient to express the rms response, z, in particular modes in terms of the buffet excitation parameter, given by Ref. 21.…”

Section: Buffetingmentioning

confidence: 99%

Unsteady aerodynamics: retrospect and prospect

Mabey¹

1999

Aeronaut. j.

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“…These phenomena lead in most cases to self-excited instabilities (buffeting), which result in unsteady airfoil loading and considerable noise generation. Self-excited airfoil flow oscillations were the subject of interest of many authors: Naumann (1965), Karashima (1961), Meier (1974), Finke (1977), Basler (1987), Mabey (1989), Geissler (1993). Their comprehensive experimental and theoretical investigations allowed them to elucidate oscillation mechanism of this type.…”

Section: Introductionmentioning

confidence: 99%

Forced oscillations of airfoil flows

Szumowski

Meier²

1996

Experiments in Fluids

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The effect of background flow oscillations on a transonic airfoil (NACA 0012) flow was investigated experimentally. The oscillations were generated by means of a rotating plate placed downstream of the airfoil. Owing to the expansion and compression waves generated at the plate, the flow over the airfoil flow was drastically disturbed. This resulted in the presence of high intensity oscillations of a shock wave and a separation bubble on the suction surface of the airfoil. For relatively large values of the airfoil angle of attack, weak shock waves (transonic sound waves) were periodically shed upstream of the airfoil. 1

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Some aspects of aircraft dynamic loads due to flow separation

Cited by 50 publications

References 9 publications

Unsteady airloads on static airfoils through high angles of attack and in reverse flow

Unsteady airloads on static airfoils through high angles of attack and in reverse flow

Unsteady aerodynamics: retrospect and prospect

Forced oscillations of airfoil flows

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