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.

Mechanical similitude and turbulence

Abstract: This report deals with the theory of the vortex street which enables the reproduction of the mechanism of the form resistance with suitable approximation under stated conditions, although such a resistance is precluded in a fluid which is perfectly inviscid. Disregarding for the present the origination of the vortex, the stream attitude in the wake of the body may be described approximately correct by the representation of individual vortices, without transgressing the law governing the motion of such vortices in an ideal fluid. Another striking example is the theory of the induced drag of wings, which likewise shows the extent of applying the vortex equations without overstepping the bounds of the dynamics of ideal fluids.

A Method for Reducing the Base Drag of Wings with Blunt Trailing Edge

Abstract: To study the possibilities of reducing the base drag of profiles with a blunt trailing edge, experiments were performed in two low-speed wind-tunnels at the DFVLR-AVA, Gottingen, some on models between walls and some on rectangular wings with an aspect ratio of 2.5. The results show that the mean base pressure can be increased, and so the base drag reduced, by using a special form of the blunt trailing edge. The variation of local base pressure along the span, and the way in which this variation is influenced by the form of the trailing edge, is also shown. Some results for the total drag and lift are also indicated.

Jet Effects on Coflow Jet Airfoil Performance

Abstract: A control volume analysis is presented in this paper to analyze the jet effect on the coflow jet airfoil with injection and suction and on the airfoil with injection only. The formulations to calculate the duct's reactionary forces that must be included for the lift and drag calculation are given. The computational fluid dynamics solutions based on the Reynolds-averaged Navier-Stokes model are used to provide the breakdowns of lift and drag contributions from the airfoil surface force integral and jet duct's reactionary forces. The results are compared with experiment for validation. The duct reactionary forces are also validated with the result of a 3-D computational fluid dynamics calculation of the complete airfoil with jet ducts and wind tunnel walls. The study indicates that the suction occurring on the airfoil suction surface of the coflow jet airfoil is more beneficial than the suction occurring through the engine inlet such as the airfoil with injection only. For the airfoil with injection only, the drag actually acted on the aircraft, or the equivalent drag, is significantly larger than the drag measured by the wind tunnel balance due to the ram drag and captured area drag when the jet is drawn from the freestream. For a coflow jet airfoil, the drag measured by the wind tunnel balance is the actual 2-D drag that the aircraft will experience. A coflow jet airfoil does not have the ram drag and captured area drag. For a coflow jet airfoil, the suction penalty is offset by the significant circulation enhancement The coflow jet airfoil with both injection and suction yields stronger mixing, larger circulation, more filled wake, higher stall angle of attack, less drag, and lower energy expenditure.

Wind Tunnel Experiments to Assess the Effect of Back-Mounted Radio Transmitters on Bird Body Drag

Abstract: To whom reprint requests should be addressed. The aerodynamic drag of bird bodies was measured in a wind tunnel, with and without back-mounted dummy radio transmitters. Flight performance estimates indicate that the drag of a large transmitter can cause a substantial reduction of a migrant9s range, that is, the distance it can cover in non-stop flight. The drag of the transmitter can be reduced by arranging the components in an elongated shape, so minimizing the frontal area. The addition of a rounded fairing to the front end, and a pointed fairing behind, was found to reduce the drag of the transmitter by about onethird, as compared with an unfaired rectangular box.