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.

A flight investigation of the boundary-layer characteristics and profile drag of the NACA 35-215 laminar-flow airfoil at high Reynolds numbers

Abstract: Report presenting testing to determine the boundary layer characteristics and profile drag of the NACA 35-215 airfoil section at high Reynolds numbers. The results indicated that a forward movement of the transition point occurred at about 3 percent of the chord due to operation of the engines and propellers.

Passive Shock Control Concept for Drag Reduction in Transonic Flow

Abstract: The operating principle of a novel passive shock control concept for drag reduction on swept wings called D-Strips is introduced, and results of a first experimental proof of concept are presented. Wind-tunnel experiments are conducted at transonic airspeeds using an airfoil VC-Opt (9.2% relative thickness) with forced boundary-layer transition. Schlieren pictures confirm the operating principle. Wake measurements demonstrate that, locally, in the wake of D-Strips the total drag increases. However, more globally, at spanwise locations away from these positions the total drag is measurably reduced if a sufficiently strong shockwave is present above the wing-suction-side surface. In contrast to passive control by ventilation, outside of the wake of the D-Strips a wave and viscous drag reduction and observed. Furthermore, the maximum lift tends to be increased by D-Strips suggesting that the buffet-onset limit is delayed. An application of D-Strips to a swept wing at cruise conditions can yield net aircraft drag reduction because the drag rise is limited to the D-Strips and its wake, but the shock-weakening effect and the drag reduction are distributed in the wide-splayed characteristics upstream of the shock front. The effectiveness of D-Strips is less sensitive to the location of the shock wave than control concepts like two-dimensional bumps, which are only effective at the design conditions. Another application of D-Strips that can be considered is the regions with a distinct shock, for example, between engines or in the wing-root region or at the inboard engine. However, there is a need for further investigations in order to optimize D-Strips and to quantify their impact on aircraft performance. Recent experimental results indicate that airscoop-type configurations might perform better as D-Strips than Velcro-type strips. Because D-Strips are easy to apply on existing wings, an application of D-Strips for retrofit is possible.

Two-dimensional wind tunnel tests of an h-34 main rotor airfoil section

Abstract: : Tests were conducted in the two-dimensional channel of the United Aircraft Corporation 8 foot wind tunnel at Mach Numbers from 0.30 to 0.80 to determine the surface pressure distributions on a Sikorsky H-34 main rotor production blade section. Twenty-nine static pressure taps were located on the upper and lower surfaces of the model. In addition three component force and moment measurements, were obtained, along with a limited amount of wake survey drag data. The pressure coefficients are tabulated for each Mach Number and angle of attack. The variation of force and moment coefficient with angle of attack at each Mach Number is also included.

Experimental investigation of aerodynamic flow over a bluff body in ground proximity with drag reduction devices

Abstract: An experimental investigation of several drag reduction devices installed in the rear of a bluff body with square back geometry in ground proximity has been conducted. The experiments include drag, base pressure measurements and velocity measurements using particle image velocimetry (PIV). The results of the drag and base pressure measurements show that significant reductions of the total aerodynamic drag (as high as 48%) can be achieved. The results also indicated that models with base cavity have lower drag than their counterparts without it. The base pressure distributions showed a strong effect of the ground, resulting in decrease of pressure towards the lower half of the base. The devices were found to have a strong effect on the underbody flow. For the drag reduction devices a rapid upward deflection of the underbody flow in the near wake was observed. The devices were also found to reduce the turbulent intensities in the near wake region.