Aerodynamics of Low Reynolds Number Flyers

Shyy, Wei; Lian, Yongsheng; Tang, Jian; Viieru, Dragos; Líu, Hao

doi:10.1017/cbo9780511551154

Cited by 608 publications

(504 citation statements)

References 203 publications

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“…[1][2][3][4][5][6][7] Moreover, the aerodynamics of low-aspect-ratio wings has also been investigated in low Reynolds number flows because some unmanned air vehicles use low-aspect-ratio wings. [4][5][6][7][8][9][10] Aerodynamic hysteresis was frequently observed in the previous studies. Here, when the aerodynamic coefficients of a wing become multiple-valued with respect to the angle of attack, it is referred to as aerodynamic hysteresis.…”

Section: Introductionmentioning

confidence: 99%

Aerodynamic Characteristics of Low-Aspect-Ratio Wings with Various Aspect Ratios in Low Reynolds Number Flows

Mizoguchi

Kajikawa

Itoh

2016

Trans. Japan Soc. Aero. S Sci.

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The effect of the aspect ratio on the stall characteristics of low-aspect-ratio wings is experimentally investigated at a Reynolds number of 5.2©10 4 . The aspect ratio ranges from 0.5 to 1.5 at intervals of 0.1. The aerodynamic coefficients of thin rectangular wings are measured in a low-speed wind tunnel. It is found that the aerodynamic characteristics of lowaspect-ratio wings are significantly sensitive to the aspect ratio. The maximum lift coefficient increases as the aspect ratio decreases toward unity. On the other hand, the difference in lift-to-drag ratio is negligible at large angles. Hysteresis during a stall occurs when the aspect ratio is within a narrow range. The span of the hysteresis loop has its peak at an aspect ratio of 1.0. The discussion also includes the analysis of lift components and flow visualization.

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Section: Introductionmentioning

confidence: 99%

Aerodynamic Characteristics of Low-Aspect-Ratio Wings with Various Aspect Ratios in Low Reynolds Number Flows

Mizoguchi

Kajikawa

Itoh

2016

Trans. Japan Soc. Aero. S Sci.

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“…For the 2D case, the small freestream velocity results in a Reynolds number Re ∞ = ρU ∞ c/μ = 4 × 10 3 and the reduced frequency is k c = ωc/2U ∞ = 1.59. In hovering, the wing tip velocity may be used as the reference velocity (Shyy et al, 2008). Identifying the peak velocity of the plunging motion as V induced = Hω, the induced Reynolds number and the reduced frequency could be recovered as Re f = ρV induced c/μ = 9.5 × 10 3 and k induced = ωc/2V induced = 0.67, respectively.…”

Section: Standard 2d Test Casementioning

confidence: 99%

“…A great deal of progress has been made in the past decade in understanding the flapping-wing aerodynamics. Mueller (2001), Shyy, Lian, Tang, Viieru, and Liu (2008), Platzer, Jones, Young, and Lai (2008) and Ol (2010) provided broader collection and detailed review of previous research work in flapping-wing aerodynamics at very low Reynolds numbers. It was first recognized by Knoller (1909) and Betz (1912) that a flapping airfoil generates thrust.…”

Section: Introductionmentioning

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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“…There are a large amount of review articles to summarize the research progress of flapping-wing aerodynamics on various aspects (Ho et al, 2003;Platzer et al, 2012;Shyy et al, 2008;Wang, 2005). Knoller (1909) and Betz (1912) were among the first to propose an inviscid theory to explain that a flapping airfoil/wing can generate thrust.…”

mentioning

confidence: 99%

An experimental study of the effects of pitch-pivot-point location on the propulsion performance of a pitching airfoil

Tian

Bodling

Liu

et al. 2016

Journal of Fluids and Structures

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a b s t r a c tAn experimental investigation was conducted to characterize the evolution of the unsteady vortex structures in the wake of a pitching airfoil with the pitch-pivot-point moving from 0.16C to 0.52C (C is the chord length of the airfoil). The experimental study was conducted in a low-speed wind tunnel with a symmetric NACA0012 airfoil model in pitching motion under different pitching kinematics (i.e., reduced frequency k ¼3.8-13.2). A high-resolution particle image velocimetry (PIV) system was used to conduct detailed flow field measurements to quantify the characteristics of the wake flow and the resultant propulsion performance of the pitching airfoil. Besides conducting "free-run" PIV measurements to determine the ensemble-averaged velocity distributions in the wake flow, "phase-locked" PIV measurements were also performed to elucidate further details about the behavior of the unsteady vortex structures. Both the vorticity-moment theorem and the integral momentum theorem were used to evaluate the effects

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Aerodynamics of Low Reynolds Number Flyers

Cited by 608 publications

References 203 publications

Aerodynamic Characteristics of Low-Aspect-Ratio Wings with Various Aspect Ratios in Low Reynolds Number Flows

Aerodynamic Characteristics of Low-Aspect-Ratio Wings with Various Aspect Ratios in Low Reynolds Number Flows

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

An experimental study of the effects of pitch-pivot-point location on the propulsion performance of a pitching airfoil

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