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.

Lift/Drag Ratios of Optimised Slewed Elliptic Wings at Supersonic Speeds

Abstract: Previous work by R. T. Jones on the drag minimisation of elliptic wings is extended to the case of the slewed wing with thickness. These results are used to calculate lift/drag ratios of idealised configurations related to a supersonic transport aircraft. The values of lift/drag ratio and optimum slenderness ratio found are comparable with those calculated earlier in studies of delta-like plan forms.

Minimum Trimmed Drag and Optimum c.g. Position

Abstract: An analytical expression is developed which shows that wing/tail interference drag is determined by wing downwash at downstream infinity. With the use of this expression, relations for minimum trimmed drag and optimum e.g. position are presented in explicit form. From this it follows that minimum induced drag is less for the combination of wing-plus-tail than for the wing alone. It is shown that this is true even for the case when the optimum tail load is a download rather than an upload. Furthermore, it is shown which are the factors that have a decisive effect on optimum e.g. position.

Full-scale investigation of the maximum lift and flow characteristics of an airplane having approximately triangular plan form

Abstract: : Procedures leading to use of sharp leading-edge wings to improve maximum rift coefficient are presented along with discussions of aerodynamic phenomena involved and curves showing aerodynamic characteristics of DM-1 glider. Airfoils with sharp leading edges, or small leading edge radii, will have satisfactory low-speed characteristics when used with highly swept-back wings. Flow over triangular wings is characterized by vortexes over wings, inboard of tips. High lift/drag ratio produces prohibitive power-off glide angle.

Measuring Aerodynamic Interference Drag Between a Bird Body and the Mounting Strut of a drag Balance

Abstract: 1.The drag of a bird body mounted on the strut of a drag balance in a wind tunnel is more than the sum of the drags of the isolated strut and the isolated body. The strut changes the air flow around the body and generates additional drag, known as interference drag. This paper describes practical methods for measuring the drag of bird bodies: a strain-gauge drag balance, dimensions for struts made with machine or hand tools, and a procedure for correcting drag measurements for interference drag. 2.Interference drag can be measured by extrapolating a relationship between the drag of isolated struts with different crosssectional sizes and shapes and the drag of a body mounted on those struts. The interference length the length of an isolated strut that produces drag equal to the interference drag is a usefulquantity for predicting interference drag. 3.The relationship mentioned above is a straight line for a model peregrine falcon (Falco peregrinus L.) body mounted on smooth struts struts with convex cross-sectional shapes ranging from streamlined to circular. This finding simplifies the determination of interference drag in three ways: (i) the line can be found from measurements with just two struts a standard strut with low drag and a calibration strut with high drag; (ii) the two struts need not have the same shape for example, the standard strut can be changed to a calibration strut by attaching a spoiler without disturbing the body mounted on the strut and (iii) a single value of interference length (33.1mm) describes smooth struts with a range of shapes and sizes. These struts had drag coefficients between 0.33 and 0.91 at Reynolds numbers between 2100 and 10800. 4.The interference length of a strut supporting the actual falcon body with a feathered surface is not significantly different from that of the strut supporting the model body with a rigid surface. 5.As a hypothesis, interference length (hI, in metres) of a smooth strut varieswith the size of the body mounted on it: hI=0.0365m0.333 where m is the body mass (in kg) of the intact bird.

Assessment of scale effects, viscous forces and induced drag on a point-absorbing wave energy converter by CFD simulations

Abstract: This paper analyses the nonlinear forces on a moored point-absorbing wave energy converter (WEC) in resonance at prototype scale (1:1) and at model scale (1:16). Three simulation types were used: Reynolds Averaged Navier–Stokes (RANS), Euler and the linear radiation-diffraction method (linear). Results show that when the wave steepness is doubled, the response reduction is: (i) 3% due to the nonlinear mooring response and the Froude–Krylov force; (ii) 1–4% due to viscous forces; and (iii) 18–19% due to induced drag and non-linear added mass and radiation forces. The effect of the induced drag is shown to be largely scale-independent. It is caused by local pressure variations due to vortex generation below the body, which reduce the total pressure force on the hull. Euler simulations are shown to be scale-independent and the scale effects of the WEC are limited by the purely viscous contribution (1–4%) for the two waves studied. We recommend that experimental model scale test campaigns of WECs should be accompanied by RANS simulations, and the analysis complemented by scale-independent Euler simulations to quantify the scale-dependent part of the nonlinear effects.