Improvement of Airfoils Aerodynamic Efficiency by Thermal Camber Phenomenon at Low Reynolds Number

Samiee, Ahmad; Djavareshkian, Mohammad Hassan; Feshalami, Behzad Forouzi; Esmaeilifar, Esmaeil

doi:10.5028/jatm.v10.954

Cited by 10 publications

(7 citation statements)

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“…Even though we reached temperature differentials between dorsal wing surfaces and the surrounding air of only 15 K, while previous studies applied differential temperatures of up to 200 K for aerofoils, we hypothesize that a similar mechanism of friction drag reduction is responsible for the observed decrease in total drag [23–28]. Future studies should apply flow characterizations on live birds flying under a heat source using particle image velocimetry and pressure distribution measurements to determine transition and separation points in the function of temperature and enable the linkage of changes in these locations to changes in lift and drag.…”

Section: Resultsmentioning

confidence: 80%

“…Simulated flight conditions have shown that aerofoil heating persists even when the wing is in motion [21]. Interestingly, multiple studies on artificial aerofoils have shown that wing surface heating can have both a positive and negative effect on flight efficiency, through changes in both lift and drag [22][23][24][25][26][27][28][29][30]. However, these studies were conducted in flow regimes ranging from laminar to turbulent (Reynolds number Re = 3000-300 000 000), using different aerofoil shapes (symmetrical or non-symmetrical) and imposing different wing surface temperatures of up to 400 K. Whether radiative heating improves the ratio between lift and drag on real bird wings, under realistic flight conditions and wing surface temperatures, remains unknown.…”

Section: Introductionmentioning

confidence: 99%

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The evolution of darker wings in seabirds in relation to temperature-dependent flight efficiency

Rogalla

Nicolaï

Porchetta

et al. 2021

J. R. Soc. Interface.

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Seabirds have evolved numerous adaptations that allow them to thrive under hostile conditions. Many seabirds share similar colour patterns, often with dark wings, suggesting that their coloration might be adaptive. Interestingly, these darker wings become hotter when birds fly under high solar irradiance, and previous studies on aerofoils have provided evidence that aerofoil surface heating can affect the ratio between lift and drag, i.e. flight efficiency. However, whether this effect benefits birds remains unknown. Here, we first used phylogenetic analyses to show that strictly oceanic seabirds with a higher glide performance (optimized by reduced sink rates, i.e. the altitude lost over time) have evolved darker wings, potentially as an additional adaptation to improve flight. Using wind tunnel experiments, we then showed that radiative heating of bird wings indeed improves their flight efficiency. These results illustrate that seabirds may have evolved wing pigmentation in part through selection for flight performance under extreme ocean conditions. We suggest that other bird clades, particularly long-distance migrants, might also benefit from this effect and therefore might show similar evolutionary trajectories. These findings may also serve as a guide for bioinspired innovations in aerospace and aviation, especially in low-speed regimes.

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Section: Resultsmentioning

confidence: 80%

Section: Introductionmentioning

confidence: 99%

The evolution of darker wings in seabirds in relation to temperature-dependent flight efficiency

Rogalla

Nicolaï

Porchetta

et al. 2021

J. R. Soc. Interface.

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“…2. 2(3) Constant velocity and constant pressure are considered as boundary conditions at the entrance and outlet, respectively (Samiee et al 2018). In order to prevent any disturbances at the boundaries, the computational domain extended 20C from the airfoil in all directions (Bos et al 2008;Lentink and Gerritsma 2003).…”

Section: Mesh and Boundary Conditionsmentioning

confidence: 99%

Numerical Simulation of a Pitching Airfoil Under Dynamic Stall of Low Reynolds Number Flow

Honarmand

Djavareshkian

Feshalami

et al. 2019

J.Aerosp. Technol. Manag.

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In this research, viscous, unsteady and turbulent fluid flow is simulated numerically around a pitching NACA0012 airfoil in the dynamic stall area. The Navier-Stokes equations are discretized based on the finite volume method and are solved by the PIMPLE algorithm in the open source software, namely OpenFOAM. The SST k - ω model is used as the turbulence model for Low Reynolds Number flows in the order of 105. A homogenous dynamic mesh is used to reduce cell skewness of mesh to prevent non-physical oscillations in aerodynamic forces unlike previous studies. In this paper, the effects of Reynolds number, reduced frequency, oscillation amplitude and airfoil thickness on aerodynamic force coefficients and dynamic stall delay are investigated. These parameters have a significant impact on the maximum lift, drag, the ratio of aerodynamic forces and the location of dynamic stall. The most important parameters that affect the maximum lift to drag coefficient ratio and cause dynamic stall delaying are airfoil thickness and reduced frequency, respectively.

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“…The flow regime that recently has been very popular among scientists is low Reynolds numbers because many micro aerial vehicles work in this range. Popularity of sinusoidal leading-edge wings in low Reynolds numbers could be attributed to their efficiency as a means of the flow control to improve aerodynamics of micro aerial vehicles compared to traditional methods like thermal camber phenomenon [7] or boundary layer suction [8]. While classical flow control methods are very energy consuming and also lead to a weight penalty, sinusoidal leading-edge wings as a way of passive flow control would be a remarkable achievement.…”

Section: Introductionmentioning

confidence: 99%

Experimental study of low Reynolds number effects on aerodynamics of smooth and sinusoidal leading-edge wings in the vicinity of the ground

Mehraban

Djavareshkian

2021

JMES

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Present study experimentally investigates the effects of ground clearance and Reynolds number on aerodynamic coefficients of smooth and sinusoidal leading-edge wings. Wind tunnel tests are conducted over a wide range of angles of attack from zero to 36 degrees, low Reynolds numbers of 30,000, 45,000 and 60,000, and also ground clearances of 0.5, 1 and ∞. Results showed that reduction of ground clearance and increment of Reynolds number cause the lift coefficient and the lift to drag ratio of both wings to be enhanced. Furthermore, the effects of Reynolds number and ground clearance on the smooth leading-edge wing are more than the sinusoidal leading-edge one. In addition, the sinusoidal leading-edge wing shows an excellent performance in the poststall region due to producing a higher lift and also by delaying the stall angle compared to the smooth leading-edge wing.

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Improvement of Airfoils Aerodynamic Efficiency by Thermal Camber Phenomenon at Low Reynolds Number

Cited by 10 publications

References 0 publications

The evolution of darker wings in seabirds in relation to temperature-dependent flight efficiency

The evolution of darker wings in seabirds in relation to temperature-dependent flight efficiency

Numerical Simulation of a Pitching Airfoil Under Dynamic Stall of Low Reynolds Number Flow

Experimental study of low Reynolds number effects on aerodynamics of smooth and sinusoidal leading-edge wings in the vicinity of the ground

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