Journal ArticleDOI
An Experimental Investigation of an Airfoil Undergoing Large-Amplitude Pitching Motions
TLDR
In this paper, the authors performed near-surface hot-wire experiments on an airfoil undergoing large-amplitude pitching motions about its quarter chord and showed the dramatic effect of pitch rate on flow structure.Abstract:
FLOW visualization and near-surface hot-wire experiments were performed in the U.S.A.F Academy Aeronautics Laboratory subsonic wind tunnel on an airfoil undergoing large-amplitude pitching motions about its quarter chord. The experiments were conducted using a NACA 0015 airfoil at an airfoil Reynolds number of 45,000. Two cases are presented in which the angular pitching rate a is maintained constant during the motion. These two cases represent two different nondimensional pitching rates a+, where ot+ is equal to 6; nondimensionalized by the chord c and the freestream velocity U^ (a + ^ac/U^). Data for the two cases where values of a+ are equal to 0.2 and 0.6 show the dramatic effect of pitch rate on flow structure. Largescale vortical structures are seen in both cases at high angles of attack but appear much later and are of a different form for the case with the larger a+ value. These structures are very energetic, producing reverse flow velocities near the airfoil surface of 1.0-2.1 times the freestream velocity.read more
Citations
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Journal ArticleDOI
Investigation of the flow structure around a rapidly pitching airfoil
Miguel R. Visbal,J. S. Shang +1 more
TL;DR: In this paper, a numerical study is presented for unsteady laminar flow past a NACA 0015 airfoil that is pitched, at a nominally constant rate, from zero incidence to a very high angle of attack.
Journal ArticleDOI
Unsteady force generation and vortex dynamics of pitching and plunging aerofoils
TL;DR: In this paper, the effects of varying frequency and plunge amplitude for the same effective angle-of-attack time history are considered, and it is shown that for constant effective angle of attack, flow evolution is independent of Strouhal number, and as the reduced frequency is increased the leading edge vortex separates later in phase during the downstroke.
Journal ArticleDOI
Dynamic Stall in Pitching Airfoils: Aerodynamic Damping and Compressibility Effects
Thomas Corke,Flint O. Thomas +1 more
TL;DR: The topic is technologically important owing to the desire to develop next-generation rotorcraft that employ adaptive rotor dynamic stall control and large-eddy simulation could be a viable approach although it remains computationally intensive.
Journal ArticleDOI
Simulating dynamic stall in a two‐dimensional vertical‐axis wind turbine: verification and validation with particle image velocimetry data
TL;DR: In this paper, the authors investigated the impact of accurately modeling the separated shed wake resulting from dynamic stall, and the importance of validation of the flow field rather than validation with only load data.
Journal ArticleDOI
Vortex formation around an oscillating and translating airfoil at large incidences
TL;DR: In this paper, the starting flow of a two-dimensional oscillating and translating airfoil is investigated by visualization experiments and numerical calculations, and it is shown that the dominant parameter of the flow is the reduced frequency not only when it oscillates at incidences close to the static stall angle but also at larger incidences.
References
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Journal ArticleDOI
A discrete vortex method for the non-steady separated flow over an airfoil
TL;DR: In this article, a discrete vortex method was used to analyze the separated non-steady flow about a cambered airfoil, where the chordwise location of the separation point was assumed to be known from experiments or flow-visualization data.
Journal ArticleDOI
Unsteady Viscous Flow on Oscillating Airfoils
W. J. Mccroskey,J.J. Philippe +1 more
TL;DR: In this article, the importance of unsteady effects on laminar boundary layers was found to diminish rapidly with increasing longitudinal pressure gradients, whereas turbulent separation on airfoils was significantly affected by oscillatory motion when the incidence approached the stall angle.
Dynamic stall of an oscillating airfoil
TL;DR: In this article, the Navier-Stokes equations in terms of the vorticity and stream function for laminar flow were solved to determine the flow field around a modified NACA 0012 airfoil.
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Investigation of the flow structure around a rapidly pitching airfoil
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