PHASE IV PERFORMANCE TEST OF THE F-86F-40 AIRPLANE EQUIPPED WITH 6 X 3-INCH LEADING EDGE SLATS AND 12-INCH EXTENSIONS ON THE WING TIPS

1956 ◽  
Author(s):  
NORRIS J. HANKS
Keyword(s):  
Performance Test ◽  
Leading Edge ◽  
Leading Edge Slats ◽  
Wing Tips ◽  
Phase Iv

The Dassault Mirage G

1969 ◽  
Vol 73 (708) ◽  
pp. 1027-1028
Author(s):  
Henri Deplante
Keyword(s):  
Leading Edge ◽  
Variable Geometry ◽  
Relative Thickness ◽  
Trailing Edge ◽  
High Lift ◽  
Profound Knowledge ◽  
Subsonic Speed ◽  
Trailing Edge Flaps ◽  
Leading Edge Slats

The interest of wings with variable sweepback springs directly from pure commonsense and appeals to no profound knowledge of aerodynamics for its justification. To realise the advantage of variable geometry, it is enough to know that only a wing of small relative thickness is capable of good performance at supersonic speeds and that by increasing the sweepback from 20° to 70° the thickness of a wing is divided by about 2. In the advanced position, the wing offers its full span to the airstream and with high-lift devices in action (leading-edge slats and trailing-edge flaps combined), the aeroplane can develop the considerable lift necessary for take-off and landing as well as for break-through and for slow approach. Wings still advanced but slats, flaps and undercarriage retracted, the aeroplane is in excellent maximum fineness condition for protracted cruising at subsonic speed or for a long wait. As soon as transonic (Mach No of more than 0-8) or supersonic speeds are in question, the wings are progressively folded back.

On spikes and spots: strongly nonlinear theory and experimental comparisons

1995 ◽  
Vol 352 (1700) ◽  
pp. 405-424 ◽  
Keyword(s):  
Three Dimensional ◽  
Wave Interaction ◽  
Leading Edge ◽  
Wide Band ◽  
Normal Pressure ◽  
Strong Nonlinearity ◽  
Free Case ◽  
Incompressible Boundary ◽  
Tollmien Schlichting ◽  
Wing Tips

Spikes and spots are discussed mostly for incompressible boundary layers, with the emphasis towards strong nonlinearity. The distinction between forced and free disturbances then becomes blurred, as spikes and spots reproduce each other. First, the forced case is concentrated on the start of spikes. The theory used is that of the two- or three-dimensional interacting boundary layer, capturing nonlinear Tollmien-Schlichting waves, for example, or following a vortex-wave interaction. Finite-time breakup produces shortened time and length scales, yielding agreement with computations and experiments on the first spike in transition, with subsequent spot formation. After the breakup, normal pressure gradients and vortex wind-up become significant locally. Second, the free case concerns initial-value problems for spots containing a wide band of three-dimensional nonlinear disturbances. The theory points to successive nonlinear stages starting at the wing tips near the spot trailing edge but gradually entering the middle as the amplitudes increase downstream. This effect combined with shortening scales produces a spread angle near 11°, very close to the experimental observations. The overall spot structure is described briefly, including also the leading edge. Viscosity arises later in two ways; for the case mentioned above with spikes originating near the surface and also through a novel interaction influencing the global spot.

A Natural Evolution Based Numerical Optimisation Framework to Develop and Enhance Airfoil-Slat Arrangement

2019 ◽  
Author(s):  
Sushrut Kumar ◽  
Priyam Gupta ◽  
Raj Kumar Singh
Keyword(s):  
Genetic Algorithm ◽  
Fitness Function ◽  
Fuel Efficiency ◽  
Optimal Solution ◽  
Leading Edge ◽  
Initial Population ◽  
Invasive Weed ◽  
Fitness Value ◽  
Leading Edge Slats ◽  
Dynamics Simulations

Abstract Leading Edge Slats are popularly being put into practice due to their capability to provide a significant increase in the lift generated by the wing airfoil and decrease in the stall. Consequently, their optimum design is critical for increased fuel efficiency and minimized environmental impact. This paper attempts to develop and optimize the Leading-Edge Slat geometry and its orientation with respect to airfoil using Genetic Algorithm. The class of Genetic Algorithm implemented was Invasive Weed Optimization as it showed significant potential in converging design to an optimal solution. For the study, Clark Y was taken as test airfoil. Slats being aerodynamic devices require smooth contoured surfaces without any sharp deformities and accordingly Bézier airfoil parameterization method was used. The design process was initiated by producing an initial population of various profiles (chromosomes). These chromosomes are composed of genes which define and control the shape and orientation of the slat. Control points, Airfoil-Slat offset and relative chord angle were taken as genes for the framework and different profiles were acquired by randomly modifying the genes within a decided design space. To compare individual chromosomes and to evaluate their feasibility, the fitness function was determined using Computational Fluid Dynamics simulations conducted on OpenFOAM. The lift force at a constant angle of attack (AOA) was taken as fitness value. It was assigned to each chromosome and the process was then repeated in a loop for different profiles and the fittest wing slat arrangement was obtained which had an increase in CL by 78% and the stall angle improved to 22°. The framework was found capable of optimizing multi-element airfoil arrangements.

On the Weis-Fogh mechanism of lift generation

1973 ◽  
Vol 60 (1) ◽  
pp. 1-17 ◽  
Author(s):  
M. J. Lighthill
Keyword(s):  
Stokes Equations ◽  
Separation Bubble ◽  
Three Dimensional ◽  
Leading Edge ◽  
The Body ◽  
Navier Stokes ◽  
Encarsia Formosa ◽  
Concentrated Force ◽  
Stagnation Points ◽  
Wing Tips

Weis-Fogh (1973) proposed a new mechanism of lift generation of fundamental interest. Surprisingly, it could work even in inviscid two-dimensional motions starting from rest, when Kelvin's theorem states that the total circulation round a body must vanish, but does not exclude the possibility that if the body breaks into two pieces then there may be equal and opposite circulations round them, each suitable for generating the lift required in the pieces’ subsequent motions! The ‘fling’ of two insect wings of chord c (figure 1) turning with angular velocity Ω generates irrotational motions associated with the sucking of air into the opening gap which are calculated in § 2 as involving circulations −0·69Ωc2 and + 0.69Ωc2 around the wings when their trailing edges, which are stagnation points of those irrotational motions, break apart (position (f)). Viscous modifications to this irrotational flow pattern by shedding of vorticity at the boundary generate (§ 3) a leading-edge separation bubble, and tend to increase slightly the total bound vorticity. Its role in a three-dimensional picture of the Weis-Fogh mechanism of lift generation, involving formation of trailing vortices at the wing tips, and including the case of a hovering insect like Encarsia formosa moving those tips in circular paths, is investigated in § 4. The paper ends with the comment that the far flow field of such very small hovering insects should take the form of the exact solution (Landau 1944; Squire 1951) of the Navier-Stokes equations for the effect of a concentrated force (the weight mg of the animal) acting on a fluid of kinematic viscosity v and density p, whenever the ratio mg/pv2 is small enough for that jet-type induced motion to be stable.

An experimental parametric study on planar sheared wings tip devices for low-to-moderate aspect ratio wings

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Lourelay Moreira dos Santos ◽  
Guilherme Ferreira Gomes ◽  
Rogerio F. Coimbra
Keyword(s):  
Wind Tunnel ◽  
Aspect Ratio ◽  
Parametric Study ◽  
Leading Edge ◽  
Aerodynamic Characteristics ◽  
Sweep Angle ◽  
Wind Tunnel Tests ◽  
Content Type ◽  
Wing Tips ◽  
Wing Tip

Purpose The purpose of this study is to investigate the aerodynamic characteristics of a low-to-moderate-aspect-ratio, tapered, untwisted, unswept wing, equipped of sheared wing tips. Design/methodology/approach In this work, wind tunnel tests were made to study the influence in aerodynamic characteristics over a typical low-to-moderate-aspect-ratio wing of a general aviation aircraft, equipped with sheared – swept and tapered planar – wing tips. An experimental parametric study of different wing tips was tested. Variations in its leading and trailing edge sweep angle as well as variations in wing tip taper ratio were considered. Sheared wing tips modify the flow pattern in the outboard region of the wing producing a vortex flow at the wing tip leading edge, enhancing lift at high angles of attack. Findings The induced drag is responsible for nearly 50% of aircraft total drag and can be reduced through modifications to the wing tip. Some wing tip models present complex geometries and many of them present benefits in particular flight conditions. Results have demonstrated that sweeping the wing tip leading edge between 60 and 65 degrees offers an increment in wing aerodynamic efficiency, especially at high lift conditions. However, results have demonstrated that moderate wing tip taper ratio (0.50) has better aerodynamic benefits than highly tapered wing tips (from 0.25 to 0.15), even with little less wing tip leading edge sweep angle (from 57 to 62 degrees). The moderate wing tip taper ratio (0.50) offers more wing area and wing span than the wings with highly tapered wing tips, for the same aspect ratio wing. Originality/value Although many studies have been reported on the aerodynamics of wing tips, most of them presented complex non-planar geometries and were developed for cruise flight in high subsonic regime (low lift coefficient). In this work, an exploration and parametric study through wind tunnel tests were made, to evaluate the influence in aerodynamic characteristics of a low-to-moderate-aspect-ratio, tapered, untwisted, unswept wing, equipped of sheared wing tips (wing tips highly swept and tapered).

Sign in / Sign up

Export Citation Format

Share Document