Simulations of Pitch–Heave Limit-Cycle Oscillations at a Transitional Reynolds Number

Yuan, Weixing; Poirel, Dominique; Wang, Baoyuan

doi:10.2514/1.j052225

Cited by 39 publications

(27 citation statements)

References 37 publications

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“…Oscillations were restricted to a range of Reynolds numbers of 4.5 × 10 4 ≤ Re c ≤ 1.3 × 10 5 in the transitional regime. This phenomenon was attributed to nonlinearity in the aerodynamic loads provided by laminar boundary layer separation [1][2][3] leading to the so-called laminar separation flutter. Negative aerodynamic damping was confirmed through large-eddy simulations (LES) of an airfoil under prescribed pitching motion 2 and later with an aeroelastic LES simulation of the airfoil in 1DOF pitch.…”

Section: Introductionmentioning

confidence: 98%

“…1,4,5 High frequency instabilities or von Kármán shedding are not believed to be necessary or influential to the LCO behavior. 1 Recently, pitch-heave oscillations have been explored computationally by Yuan et al 3 and experimentally by Poirel and Mendes. 6 The self-sustained oscillations at transitional Reynolds numbers described above represent a new type of aeroelastic phenomenon in contrast with the well-known stall flutter 7 resulting from flow separation that occurs at high angles of attack, or transonic flutter 7 due to large shock motions.…”

Section: Introductionmentioning

confidence: 99%

“…Negative aerodynamic damping was confirmed through large-eddy simulations (LES) of an airfoil under prescribed pitching motion 2 and later with an aeroelastic LES simulation of the airfoil in 1DOF pitch. 3 The unsteady processes that appear to drive the sustained oscillations are sensitive to a number of external factors. For instance, tripping the laminar boundary layer or introducing free stream turbulence can suppress pitching oscillations.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Aeroelastic Response of an Airfoil at Transitional Reynolds Numbers

Barnes

Visbal

2016

46th AIAA Fluid Dynamics Conference

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This work explores self-sustained pitching oscillations of a NACA0012 airfoil operating at low-to-moderate Reynolds numbers in which the aerodynamic flow is in a transitional regime. One-degree of freedom (1-DOF) pitching oscillations are explored over a range of chord-based Reynolds numbers (7.7 × 10 4 < Rec ≤ 2.0 × 10 5 ). Additionally, several initial angles of attack and a wide range of torsional stiffnesses are evaluated at a single Reynolds number of Rec = 1.1 × 10 5 . Limit cycle oscillation (LCO) is observed at all Reynolds numbers considered but requires a disturbance to initiate at the highest flow speeds. In all cases, negative aerodynamic damping is largely provided by suction beneath a separation bubble located behind the elastic axis. This feature induces a moment that reinforces the pitch-rate at small angles of incidence. Open trailing edge separation on the opposite surface transitions and reattaches immediately preceding the largest angles of incidence. This process imparts a spike in the pitching moment that opposes the pitch-rate and briefly damps oscillations. Transition of the detached shear layer occurs at lower angles of incidence as Reynolds number is increased, attenuating oscillation amplitude. The LCO behavior appears to require both transition of the flowfield and sufficient lag in the development/response of the transitional flow. Simulations at a nonzero initial angle of attack demonstrate the same LCO can emerge in non-symmetric conditions while a study on the effects of structure rigidity reveal transition flutter persists over several orders of magnitude for spring stiffness. A stiffer airfoil can adjust the timing of flow transition processes in the cycle and by extension modify the aerodynamic hysteresis.

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Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Aeroelastic Response of an Airfoil at Transitional Reynolds Numbers

Barnes

Visbal

2016

46th AIAA Fluid Dynamics Conference

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“…The code has been used for a number of applications including largeeddy and unsteady Reynolds-averaged Navier-Stokes simulations (Yuan, Poirel, Wang, & Benaissa, 2014), low-Reynolds flows (Yuan, Khalid, Windte, Scholz, & Radespiel, 2007), laminar-separation flutter (Yuan, Poirel, & Wang, 2013), and flapping-wing aerodynamics (Yuan et al, , 2010.…”

Section: Description Of the In-house Cfd Solvermentioning

confidence: 99%

Experimental and computational investigations of flapping wings for Nano-air-vehicles

Yuan

Lee

Levasseur

2015

Engineering Applications of Computational Fluid Mechanics

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This paper presents the finalized results of a recent project which investigated the aeromechanical aspects of aerodynamic force generation by making use of flapping wings. Flapping-wing experiments using small wings have some unique challenges posed by the low force level ( ∼ 1 N) and the cyclic wing motion. A tailored experimental water tunnel facility was developed for flapping wings operating at high reduced frequency with a complex two-dimensional and a three-dimensional motion profile. The experimental capability is demonstrated by the test cases of two-dimensional and three-dimensional flapping wings, designed according to a proposed notional nano-air-vehicle at a hovering condition. The features of the water tunnel, the geometric and kinematic parameters of the airfoils/wings, and the setups of the motion rigs for each test case are described. Measured forces and particle image velocimetry data are analyzed and cross-checked with the numerical results obtained from a code developed in-house. The comparisons of the experimental and numerical results show that the established experimental approach obtained a quantitatively reliable solution for the development of flapping wings and can serve for numerical validation of engineering tool developments. The investigation reveals that the kinematics of a rigid airfoil or wing is the dominant influence in the generation of aerodynamic forces, while the cross-section profile plays a secondary role. An asymmetric-wake-in-time is found behind the single airfoils and wings, which contributes to an asymmetry behavior of the resulting aerodynamic forces. In addition to the findings of single airfoils and wings, further analyses of the numerical and experimental results confirm that wing-wing interaction through the clap-fling mechanism can intensify the generation of the thrust force while accompanied by a small reduction in the overall propulsion efficiency.

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“…The in-house, block-structured, incompressible code INS §ow [5,6] was used for the HQ309, SD7032, and SD7037 airfoil §ow calculations. The code is applicable to small UAVs when the Mach number is less than 0.3.…”

Section: Computational Fluid Dynamics Solversmentioning

confidence: 99%

In-flight icing on unmanned aerial vehicle and its aerodynamic penalties

Szilder

Yuan

2017

Progress in Flight Physics

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A numerical prediction of ice accretion on HQ309, SD7032, and SD7037 airfoils and its aerodynamic penalties is described. Ice accretion prediction on a three-dimensional (3D) swept wing is also presented. In addition to air §ow and drop trajectory solvers, NRC£s (National Research Council) original, 3D, morphogenetic icing modeling approach has been used. The analysis was performed for a wide range of icing conditions identi¦ed in the FAA (Federal Aviation Administration) Appendix C icing envelope. They cover a range of drop sizes, air temperatures, and liquid water contents. For selected icing conditions, the resulting decrease in lift and increase in drag have been calculated.

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Simulations of Pitch–Heave Limit-Cycle Oscillations at a Transitional Reynolds Number

Cited by 39 publications

References 37 publications

Aeroelastic Response of an Airfoil at Transitional Reynolds Numbers

Aeroelastic Response of an Airfoil at Transitional Reynolds Numbers

Experimental and computational investigations of flapping wings for Nano-air-vehicles

In-flight icing on unmanned aerial vehicle and its aerodynamic penalties

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