Drag on an Oscillating Airfoil in a Fluctuating Free Stream

Kottapalli, Sesi; Pierce, G. A.

doi:10.1115/1.3448985

Cited by 16 publications

(4 citation statements)

References 23 publications

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“…Although some experimental research regarding unsteady inflow effects on pitching airfoils has been performed, much less computational work has been done in this area due to the difficulty of coupling nonuniform inflow conditions with a dynamic pitching motion in computational models. In the 1970s, Pierce et al [2] and Kottapalli and Pierce [20] performed experiments on pitching helicopter blades with cyclic inflow conditions, showing that these inflow conditions affected the forces and moments on the blade with varying magnitudes dependent upon the phase difference between the airfoil oscillation and inflow velocity oscillation. A similar study by Shi and Ming [5,6] investigated a pitching delta wing, for improvements in the design of supermaneuverable aircraft.…”

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confidence: 99%

Effect of Impinging Wake Turbulence on the Dynamic Stall of a Pitching Airfoil

Merrill

Peet

2017

AIAA Journal

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Dynamically moving airfoils are encountered in helicopter rotors, wind-turbine blades, and maneuvering aircraft. A clearer understanding of how freestream disturbances affect the aerodynamic forces on pitching airfoils leads to improved designs. In the present study, the authors' recently validated spectrally accurate moving overlapping mesh methodology is used to perform a direct numerical simulation of a NACA 0012 airfoil pitching with oscillatory motion in the presence of a turbulent wake created by an upstream solid cylinder. The global computational domain is decomposed into a stationary background mesh, which contains the solid cylinder, and a mesh constructed around the airfoil that is constrained to pitch with predetermined reduced frequency k 0.16. Present simulations are performed with chord-based Reynolds number Re c 44;000. Aerodynamic forces and vortex-shedding properties are compared between the pitching airfoil simulations with and without upstream disturbances. Power spectral density functions of the aerodynamic forces and moments are investigated to further determine the effect of a turbulent wake on a pitching airfoil.

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confidence: 99%

Effect of Impinging Wake Turbulence on the Dynamic Stall of a Pitching Airfoil

Merrill

Peet

2017

AIAA Journal

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“…They also found that the dynamic stall starts at a later time at high angle of attacks due to delayed formation and detachment of the dynamic stall vortex. Several other previous researchers [15][16][17][18][19][20][21] have demostrated that the impact of unsteady inflow on aerodynamic loads is also applicable to helicopters and maneuverable wings working in the environment with freestream velocity fluctuations.…”

Section: Introductionmentioning

confidence: 99%

Numerical Study of Flapping-Wing Flow Physics in Nonuniform Freestream Using the High-Order Spectral Difference Method on Dynamic Unstructured Grids

Poudel

2018

2018 Fluid Dynamics Conference

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In this paper, a numerical study is conducted to understand the impact of nonuniform freestream on the aerodynamic performance of a flapping foil. Specifically, an unsteady flow environment is generated by stationary inline or staggered circular cylinder arrays upstream. A 2D NACA0012 airfoil is then placed at different locations downstream of the cylinder arrays, and oscillates in the nonuniform freestream. Unsteady flows over the flapping foil are numerically simulated by solving the 2D low-Mach-number-preconditioned compressible Naiver-Stokes equations on deformable unstructured grids using the high-order spectral difference method. The flow fields over a pitching airfoil in unsteady flow environments and the corresponding aerodynamic forces are analyzed and compared under different flow conditions. It is observed that the nonuniform freestream can significantly affect the unsteady vortex dynamics of a flapping foil, thus modifying the thrust and lift generation.

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“…At the present time, some experimental research has been performed to examine the effects of unsteady inflow on pitching airfoils, while a much smaller amount of computational work has been done in this area. In the 1970's Pierce et al 2 and Kottapalli et al 15 performed experiments on pitching helicopter blades using a gust generator to produce periodic inflow conditions. Their results show that the varying freestream velocity affects the pitching moment and drag experienced by the blade, and that the magnitudes of the forces and moment change depending on the phase difference between the airfoil oscillation and inflow velocity oscillation.…”

Section: Introductionmentioning

confidence: 99%

Effects of Upstream Disturbances on a Pitching NACA0012 Airfoil

Merrill

Peet²

2016

54th AIAA Aerospace Sciences Meeting

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Dynamically moving airfoils are encountered in several areas of flight and energy production, including helicopter rotors, wind turbine blades, and maneuvering aircraft. A clearer understanding of how freestream disturbances affect the aerodynamic forces on pitching airfoils leads to improvements in aircraft and wind turbine design. In the present study, our recently validated moving overlapping mesh methodology is used to perform a direct numerical simulation of a NACA0012 airfoil pitching with oscillatory motion in the presence of a turbulent wake created by an upstream cylinder. The global computational domain is decomposed into a stationary background mesh, which contains the cylinder, and a mesh constructed around the airfoil that is constrained to pitch with predetermined reduced frequency, k=0.16. Present simulations are performed with chord based Reynolds number Rec = 44, 000, with aerodynamic forces and vortex shedding properties being compared between the pitching airfoil simulations with and without upstream disturbances.

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Drag on an Oscillating Airfoil in a Fluctuating Free Stream

Cited by 16 publications

References 23 publications

Effect of Impinging Wake Turbulence on the Dynamic Stall of a Pitching Airfoil

Effect of Impinging Wake Turbulence on the Dynamic Stall of a Pitching Airfoil

Numerical Study of Flapping-Wing Flow Physics in Nonuniform Freestream Using the High-Order Spectral Difference Method on Dynamic Unstructured Grids

Effects of Upstream Disturbances on a Pitching NACA0012 Airfoil

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