Lift-induced drag

About: Lift-induced drag is a research topic. Over the lifetime, 2861 publications have been published within this topic receiving 41094 citations.

Effects of Leaders Position and Shape on Aerodynamic Performances of V Flight Formation

Abstract: The influences of the leader in a group of V – flight formation are dealt with. The investigation is focused on the effect of its position and shape on aerodynamics performances of a given V – flight formation. Vortices generated the wing tip of the leader moves downstream forming a pair of opposite rotating line vortices. These vortices are generally undesirable because they create a downwash that increases the induced drag on leader’s wing. However, this downwash is also accompanied by an upwash that can beneficial to the follower’s wing flying behind the leader’s one, namely a favorable lift for the follower’s wing. How much contributions of the leader’s wing to the follower’s wing in the V – formation flight is determined by the strength of tip vortices generated by the leader’s wing which is influenced by its position and shape including incidence angle, dihedral angle, aspect ratio and taper ratio. The prediction of aerodynamic performances of the V–flight formation including lift, drag and moment coefficients is numerically performed by solving Navier – Stokes equations with k - e turbulence model. The computational domain is defined with multiblock topology to capture the complex geometry arrangement of the V – flight formation.

Aircraft Drag Reduction

Abstract: This paper reviews aerodynamic drag reduction for friction, wave and vortex drag associated with supersonic cruise aircraft and suggests approaches and research directions which cover the spectrum from possibly significant to revolutionary. Various synergisms are also included, especially in regard to suction laminar flow control and flow separation control at cruise. The former may also enable improved low speed, high lift systems, lift to drag ratio for subsonic cruise, reduced parasitic viscous drag for favorable interference wave drag reduction approaches, and turbulent skin friction reduction via slot injection. Flow separation control at cruise proffers opportunities for increased leading edge thrust, increased lift increment from upper surface, increased fuselage lift/camber for wave drag due to lift reduction, improved performance of various favorable interference wave drag reduction schemes, as well as possibly better low speed, high-schemes and wing cruise performance. More speculative approaches include multi-stage aircraft, thrust vectoring for lift augmentation, as well as trim, and a number of conceptual wave and vortex drag reduction schemes.

Flight tests of external modifications used to reduce blunt base drag

Abstract: The effectiveness of a trailing disk (the trapped vortex concept) in reducing the blunt base drag of an 8-in diameter body of revolution was studied from measurements made both in flight and in full-scale wind-tunnel tests. The experiment demonstrated the significant base drag reduction capability of the trailing disk to Mach 0.93. The maximum base drag reduction obtained from a cavity tested on the flight body of revolution was not significant. The effectiveness of a splitter plate and a vented-wall cavity in reducing the base drag of a quasi-two-dimensional fuselage closure was studied from base pressure measurements made in flight. The fuselage closure was between the two engines of the F-111 airplane; therefore, the base pressures were in the presence of jet engine exhaust. For Mach numbers from 1.10 to 1.51, significant base drag reduction was provided by the vented-wall cavity configuration. The splitter plate was not considered effective in reducing base drag at any Mach number tested.

Lift and Drag of Wings with Small Span

Abstract: The lift coefficient of!a wing of small span at first shows a linear increase for the increasing angle of attack, but to a lesser degree then was to be expected according to the theory of the lifting line; thereafter the lift coefficient increases more rapidly than linearity, as contrasted with the the theory of the lifting line. The induced drag coefficient for a given lift coefficient, on the other hand, is obviously much smaller than it would be according to the theory. A mall change in the theory of the lifting line will cover these deviations.

Computational Study of Influences of a Seam Line of a Ball for Baseball on Flows

Abstract: Flows around a ball used in baseball games are calculated using third-order upwind-difference method with various seam positions determined by two rotation angles Those are four-seam rotation with an angle: a and two-seam rotation with an angle: b The computed results of the four-seam rotation are compared with experimental data measured in a wind tunnel and computed drag coefficients qualitatively agree well with experiments However, lift coefficients do not agree well The computed results and geometrical symmetry suggest that a supporting rod in the wind tunnel would have strong influence on the accuracy of the measurement Flow changes in two-seam rotation are also simulated It is found that the lowest drag force is observed at b=90 and that the value is less than half of the largest drag force at a=30 and 60 degrees The largest lift force is observed at b=20 degree In this case, a projection of the seam line on the top causes a large separation while smooth surface without the seam at the bottom dose not separate the flow A pair of longitudinal vortices are found in the wake, which make wake slant and generate large lift force