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Airfoil

About: Airfoil is a research topic. Over the lifetime, 24696 publications have been published within this topic receiving 337709 citations. The topic is also known as: aerofoil & wing section.


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Journal ArticleDOI
TL;DR: In this paper, the effects of the modified leading edge in terms of lift-to-drag performance and the influence of camber on such parameters were investigated using the OpenFOAM solver.
Abstract: Taking a lead from the humpback whale flukes, characterized by a series of bumps that result in a sinusoidal-like leading edge, this paper reports on a three-dimensional numerical study of sinusoidal leading edges on cambered airfoil profiles. The turbulent flow around the cambered airfoil with the sinusoidal leading edge was computed at different angles of attack with the open source solver OpenFOAM, using two different eddy viscosity models integrated to the wall. The reported research focused on the effects of the modified leading edge in terms of lift-to-drag performance and the influence of camber on such parameters. For these reasons a comparison with a symmetric airfoil is provided. The research was primarily concerned with the elucidation of the fluid flow mechanisms induced by the bumps and the impact of those mechanisms on airfoil performance, on both symmetric and cambered profiles. The bumps on the leading edge influenced the aerodynamic performance of the airfoil, and the lift curves were found to feature an early recovery in post-stall for the symmetric profile with an additional gain in lift for the cambered profile. The bumps drove the fluid dynamic on the suction side of the airfoil, which in turn resulted in the capability to control the separation at the trailing edge in coincidence with the peak of the sinusoid at the leading edge.

72 citations

Proceedings ArticleDOI
15 Jan 1996
TL;DR: In this paper, the effect of large-droplet ice accretion on aircraft control and in particular lateral control is examined and it is shown that a ridge of ice aft of the boot can lead to large losses in lift, increases in drag and changes in the pitching moment.
Abstract: The effect of large-droplet ice accretion on aircraft control and in particular lateral control is examined. Supercooled large droplet icing conditions can result in the formation of a ridge of ice aft of the upper surface boot. By comparing this ice shape to data acquired with a spanwise protuberance on a different airfoil, it is clear that a ridge of ice aft of the boot can lead to large losses in lift, increases in drag and changes in the pitching moment. This effect is most likely due to the formation of a large separation bubble aft of the ice accretion which grows with angle of attack and eventually fails to reattach, leading to premature airfoil stall. The bubble alters the pressure distribution about the airfoil resulting in a more trailing edge up (negative) hinge moment on the aileron and the resulting change in aileron stick force. This can lead to aileron hinge moment reversal and aileron snatch. In aileron snatch the hinge moments are altered to the extent that the aileron is pulled up by the low pressure over the upper surface of the aileron with sufficient force to induce a rapid roll if a large stick force is not immediately exerted to oppose it. There is evidence in the literature which shows that similar lateral control problems are possible with other types of ice accretions and airfoil types.

72 citations

Journal ArticleDOI
Kristin Bishop1
TL;DR: The goal of this study was to describe the body position and performance of a gliding mammal and to identify correlates between kinematics and aerodynamic performance, and there was a strong correlation between nose-down pitching rotations and limb movements that tended to increase the angle of attack of the wing membrane.
Abstract: Gliding is the simplest form of flight, yet relatively little is known about its mechanics in animals. The goal of this study was to describe the body position and performance of a gliding mammal and to identify correlates between kinematics and aerodynamic performance. To do this, I used a pair of high-speed digital cameras to record a portion of the middle of glides by southern flying squirrels, Glaucomys volans. The squirrels launched from a height of 4 m and landed on a vertical pole. Reflective markers were applied to anatomical landmarks and the 3-D coordinates of these points were computed to describe the kinematics of the glides. From these data I estimated the lift and drag generated during the glide, and correlated these variables with gliding performance as measured by glide angle, glide speed and stability. In the majority of the glide sequences the squirrels accelerated in the downward direction and accelerated horizontally forward as they moved through the calibrated volume in the middle of the glide trajectory, rather than exhibiting a steady glide in which the body weight is balanced by the resultant aerodynamic force. Compared to human engineered airfoils, the angles of attack used by the squirrels were unexpectedly high, ranging from 35.4 degrees to 53.5 degrees , far above the angle of attack at which an aircraft wing would typically stall. As expected based on aerodynamic theory, there was a negative correlation between angle of attack and lift coefficient, indicating that the wings are stalled, and a positive correlation between angle of attack and drag coefficient. Also as expected, there was a negative correlation between lift-to-drag ratio and angle of attack, as increasing angle of attack produced both less lift and more drag. Within glides, there was a strong correlation between nose-down pitching rotations and limb movements that tended to increase the angle of attack of the wing membrane, suggesting that the animals actively control their pitch by moving their limbs. The squirrels used much steeper glide angles than those reported for other gliding animals, ranging from 40.4 degrees to 57.4 degrees . It is likely that this is because they did not launch from a great enough height to reach their minimum glide angle. In some trials the glide angle increased over the captured portion of the glide, whereas in others it decreased, and the magnitude of the changes varied substantially, rendering it difficult to ascertain which portion of the glide trajectory was represented. Decreases in glide angle were strongly correlated with increases in lift coefficient, but were uncorrelated with drag coefficient.

72 citations

Journal ArticleDOI
TL;DR: In this paper, a bistable airfoil with the actuator system and the aerodynamic loads coupled to the structure is designed to understand the aeroelastic characteristics of the system.
Abstract: A bistable airfoil with the actuator system and the aerodynamic loads coupled to the structure is designed to understand the aeroelastic characteristics of the system. The bistable flap consists of a stack of six bistable prestressed buckled laminates with the plates having dimensions of 100 × 100 mm made from Hexcel 913 glass fiber. The bistable plates attached to a spar situated at 85% chord on the rotor blade. The foam tape placed between each of the plates at the trailing edge making the airfoil weather tight. The bistable plate spar is parallel to the direction of motion of the moving crosshead of the test machine. For the flap to be in equilibrium without any actuator input, the sum of the work done on the structure by the aerodynamic loads W f and the work done on the aerodynamic loads by the structure W b is zero. The modulus function shows that the work needs to be done on the structure to rotate the flap in either direction from an equilibrium point whereas the work done on the aerodynamic loads is dependant on direction.

71 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20231,083
20221,871
2021923
2020979
20191,097
20181,002