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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.


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Journal ArticleDOI
TL;DR: Theoretical and practical aspects of conducting three-dimensional wake measurements in large wind tunnels are reviewed with emphasis on applications in low-speed aerodynamics in this paper, where the authors demonstrate the value of this measurement technique using data from wake measurements conducted on a variety of low speed configurations including the complex high-lift system of a transport aircraft.
Abstract: Theoretical and practical aspects of conducting three-dimensional wake measurements in large wind tunnels are reviewed with emphasis on applications in low-speed aerodynamics. Such quantitative wake surveys furnish separate values for the components of drag such as profile drag and induced drag, but also measure lift without the use of a balance. In addition to global data, details of the wake flowfield as well as spanwise distributions of lift and drag are obtained. This article demonstrates the value of this measurement technique using data from wake measurements conducted on a variety of low-speed configurations including the complex high-lift system of a transport aircraft.

96 citations

Journal ArticleDOI
TL;DR: In this paper, the physical mechanisms that accompany mean drag modifications in the cylinder wake flow subject to rotary control were identified. But the results of the numerical simulations at Re=150.
Abstract: In this paper we are interested in identifying the physical mechanisms that accompany mean drag modifications in the cylinder wake flow subject to rotary control. We consider simple control laws where the obstacle rotates harmonically with frequencies varying from half to more than five natural frequencies. In our investigation we analyze the results of the numerical simulations at Re=150. All the simulations were performed using the vortex method, which in the paper is outlined and benchmarked. We confirm the earlier findings concerning mean drag reduction at higher forcing frequencies and show that for the considered values of Re this control technique is energetically inefficient. The main result is that changes of the mean drag are achieved by modifying the Reynolds stresses and the related mean flow correction. The controlled flows are carefully characterized in terms of these fields. Drag reduction is related to elongation of the recirculation bubble. It is argued that mean drag reduction is associa...

96 citations

DissertationDOI
01 Jan 1947
TL;DR: In this article, the authors present the methods and concepts of the theory of linearized supersonic flow and the results for a basic thickness distribution and various lifting triangles are presented.
Abstract: This thesis is a presentation of the methods and concepts of the theory of linearized supersonic flow. The fundamental theory which serves as a basis for this investigation is discussed in the first two chapters. Special emphasis is placed upon the study of planar systems. A system of conical coordinates is introduced in which the method of separation of variables is applied. The resultant solutions have the Mach cone as a natural boundary and involve a family of hypergeometric functions related to the Legendre functions. Basic integral relations for planar systems are obtained between the normal velocity component and the component giving the pressure. The behavior of planar systems relative to the planform configuration is discussed and the concept of problems of the first and second kind is introduced. The lift problem is treated with particular reference to the behavior of the leading edge singularity and to the concept of the Kutta condition as applied to a planform in supersonic flow. The nature of drag in linearized supersonic systems is investigated and the separation of the drag into types is discussed. For planar systems the drag may be divided into basic and induced parts. For general systems the basic division may be made into wave drag and vortex drag. Two fundamental reversed flow theorems are obtained which state that the drag of a system is the same as that of the system with the flow reversed in direction. The theory of conical flow as applied to planar systems is developed and the results for a basic thickness distribution and various lifting triangles are presented. The method of the separation of the lateral variable is investigated using Schlomilch series. The flow about bodies of revolution is discussed and the application of the Riemann method to the problem is given.

96 citations

01 Jan 2003
TL;DR: In this paper, the design, development and testing of an inflatable telescopic wing that permits a change in the aspect ratio while simultaneously supporting structural wing loads is discussed. But the work is limited to a single UAV.
Abstract: This paper discusses the design, development and testing of an inflatable telescopic wing that permits a change in the aspect ratio while simultaneously supporting structural wing loads. The key element of the wing consists of a pressurized telescopic spar that can undergo large-scale spanwise changes while supporting wing loadings in excess of 15 lbs/ft. The wing cross-section is maintained by NACA0012 rib sections fixed at the end of each element of the telescopic spar. Telescopic skins are used to preserve the spanwise airfoil geometry and ensure compact storage and deployment of the telescopic wing. A small scale telescopic wing assembly was tested in a free jet wind tunnel facility at a variety of Reynolds numbers (182000, 273000, 363000 and 454000). The telescopic wing was deployed from 7 inches to 15”. Experimental wind tunnel results were compared to rigid fixed wing test specimen to compare the performance of the telescopic wing. Preliminary aerodynamic results are promising for the variable aspect ratio telescopic wing. Overall, the telescopic wing at maximum deployment did incur a slightly larger drag penalty and a reduced lift to drag ratio. Thus, it may be possible to develop UAVs with variable aspect ratio wings using inflatable telescopic spars and skin sections. Graduate Research Assistant, Aerospace Engineering Dept. † Undergraduate Student, Aerospace Engineering Dept. Associate Professor, Aerospace Engineering Dept., Associate Fellow of AIAA Nomenclature a Lift curve slope a0 Theoretical lift curve slope a Angle of attack (degrees) a i Induced angle of attack (degrees) AR Aspect ratio b Wingspan (ft) c Chord length (ft) cf Specific fuel consumption CL Lift coefficient CD Drag coefficient CD,0 Induced Drag coefficient at α = 0 CD,i Induced Drag coefficient e Span efficiency factor E Endurance ID Inside Diameter l Length L Lift force m Mass (lbs) ? Propeller efficiency μ Viscosity OD Outside Diameter P Pressure (Psi) q Dynamic pressure R Range Re Reynolds Number ? Density (lbs/ft ) S Surface area of the wing t Thickness (ft) V Speed (ft/s) W0 Gross weight (with full fuel an payload) W1 Empty weight (lbs) 8 Freestream

95 citations

Journal ArticleDOI
TL;DR: In this paper, the authors used random-textured hydrophobic surfaces (fabricated using large-length scalable thermal spray processes) on a flat plate geometry to demonstrate skin-friction reduction in the turbulent regime.
Abstract: Technologies for reducing hydrodynamic skin-friction drag have a huge potential for energy-savings in applications ranging from propulsion of marine vessels to transporting liquids through pipes. The majority of previous experimental studies using hydrophobic surfaces have successfully shown skin-friction drag reduction in the laminar and transitional flow regimes (typically Reynolds numbers less than ≃106 for external flows). However, this hydrophobicity induced drag reduction is known to diminish with increasing Reynolds numbers in experiments involving wall bounded turbulent flows. Using random-textured hydrophobic surfaces (fabricated using large-length scalable thermal spray processes) on a flat plate geometry, we present water-tunnel test data with Reynolds numbers ranging from 106 to 9 × 106 that show sustained skin-friction drag reduction of 20%–30% in such turbulent flow regimes. Furthermore, we provide evidence that apart from the formation of a Cassie state and hydrophobicity, we also need a low surface roughness and an enhanced ability of the textured surface to retain trapped air, for sustained drag reduction in turbulent flow regimes. Specifically, for the hydrophobic test surfaces of the present and previous studies, we show that drag reduction seen at lower Reynolds numbers diminishes with increasing Reynolds number when the surface roughness of the underlying texture becomes comparable to the viscous sublayer thickness. Conversely, test data show that textures with surface roughness significantly smaller than the viscous sublayer thickness and textures with high porosity show sustained drag reduction in the turbulent flow regime. The present experiments represent a significant technological advancement and one of the very few demonstrations of skin-friction reduction in the turbulent regime using random-textured hydrophobic surfaces in an external flow configuration. The scalability of the fabrication method, the passive nature of this surface technology, and the obtained results in the turbulent regime make such hydrophobic surfaces a potentially attractive option for hydrodynamic skin-friction drag reduction.

95 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202344
2022105
202138
202046
201944
201849