Topic
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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TL;DR: In this article, an evolutionary algorithm hybridized with different games (cooperative Pareto game, competitive Nash game and hierarchical Stackelberg game) for comparison is implemented to optimize the airfoil shape with a larger laminar flow range and a weaker shock wave drag simultaneously due to a shock control bump (SCB) active device.
Abstract: In order to improve the performances of a civil aircraft at transonic regimes, it is critical to develop new computational optimization methods reducing friction drag Natural laminar flow (NLF) airfoil/wing design remain efficient methods to reduce the turbulence skin friction However, the existence of wide range of favorable pressure gradient on a laminar flow airfoil/wing surface leads to strong shock waves occurring at the neighborhood of the trailing edge of the airfoil/wing Consequently, the reduction of the friction drag due to the extension of the laminar flow surface of the airfoil is compensated with an increase of the shock wave induced drag In this paper, an evolutionary algorithm (EAs) hybridized with different games (cooperative Pareto game, competitive Nash game and hierarchical Stackelberg game) for comparison is implemented to optimize the airfoil shape with a larger laminar flow range and a weaker shock wave drag simultaneously due to a shock control bump (SCB) active device Numerical experiments demonstrate that each game coupled to the EAs optimizer can easily capture either a Pareto front, a Nash equilibrium or a Stackelberg equilibrium of this two-objective shape optimization problem From the analysis/synthesis of 2D results it is concluded that a variety of laminar flow airfoils with greener aerodynamic performances can be significantly improved due to optimal SCB shape and position when compared to the baseline airfoil geometry This methodology illustrate the potentiality of such an approach to solve the challenging shape optimization of the NLF wings in industrial design environments
12 citations
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10 Sep 2008TL;DR: In this paper, a medium fidelity panel method and equivalent beam finite element model are used to explore the possibilities of non-planar lifting surface configurations taking into account the coupling between aerodynamics and structures.
Abstract: Non-planar lifting surface aircraft configurations offer potentially significant gains in aerodynamic efficiency by lowering the total induced drag. There are many options for non–planar wing configurations, from winglets and multiwings to box and joined wings. Non–aerodynamic considerations such as structures, weight and stability and control can significantly impact the overall improvements in efficiency.Here, a medium fidelity panel method and equivalent beam finite element model are used to explore the possibilities of non–planar lifting surface configurations taking into account the coupling between aerodynamics and structures. Two main cases, a single discipline aerodynamic optimization and a multidisciplinary aero–structural optimization are investigated. To demonstrate the effect of non–planar configurations, the main lifting surface of a typical commercial aircraft at cruise is optimized. The optimization of the wing configurations is geometrically constrained by a maximum projected span and height. The effect of incorporating parasitic drag in the aerodynamic model is also explored. Due to the complexity of the design space and the presence of multiple local minima, an augmented Lagrange multiplier particle swarm global optimizer is used. The particle swarm algorithm is a global optimization algorithm based on a simplified social model and is closely tied to swarming theory. The aerodynamic optimum solution found for rectangular lifting surfaces is a box wing, as predicted by theory. Allowing for sweep and taper as design variables yields a joined wing as the aerodynamic optimum result. The addition of parasitic drag in the aerodynamic model reduces the size of the non–planar elements in the topology of the aerodynamic optimum solutions. Including structures and the coupling between structures and aerodynamics in the optimization has a profound impact due to the additional weight of non–planar segments. The aero–structural optimal solution found is the C–wing configuration when parasitic drag is neglected and the addition of a winglet to the planar wing when parasitic drag is included.
12 citations
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01 Jan 1993TL;DR: In this article, an application of supersonic natural laminar flow (NLF) technology for a high speed civil transport (HSCT) configuration is presented with a 70 deg inboard leading edge sweep and a 20 deg leading-edge outboard crank.
Abstract: Results are presented of a preliminary investigation into an application of supersonic natural laminar flow (NLF) technology for a high speed civil transport (HSCT) configuration. This study focuses on natural laminar flow without regard to suction devices which are required for laminar flow control (LFC) or hybrid laminar flow control (HLFC). An HSCT design is presented with a 70 deg inboard leading-edge sweep and a 20 deg leading-edge outboard crank to obtain NLF over the outboard crank section. This configuration takes advantage of improved subsonic performance and NLF on the low-sweep portion of the wing while minimizing the wave drag and induced drag penalties associated with low-sweep supersonic cruise aircraft. In order to assess the benefits of increasing natural laminar flow wetted area, the outboard low-sweep wing area is parametrically increased. Using a range of supersonic natural laminar flow transition Reynolds numbers, these aircraft are then optimized and sized for minimum take-off gross weight (TOGW) subject to mission constraints. Results from this study indicate reductions in TOGW for the NLF concepts, due mainly to reductions in wing area and total wing weight. Furthermore, significant reductions in block fuel are calculated throughout the range of transition Reynolds numbers considered. Observations are made on the benefits of unsweeping the wingtips with all turbulent flow.
12 citations
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TL;DR: The theory of crossflow aerodynamics is used to estimate the effect of thrower-induced vibrations on the javelin mean lift and drag as mentioned in this paper, and the results show that velocities of all modes increase both lift and speed.
Abstract: The theory of crossflow aerodynamics is used to estimate the effect of thrower-induced vibrations on javelin mean lift and drag. Vibrations of all modes increase both lift and drag from the vibration-free condition. Percentage in-creases in lift and drag are largest at small mean angles of attack, large vibrational amplitudes, and large relative wind speeds. Thus the consequences of vibration effects on aerodynamics may be most significant for elite throwers.
12 citations
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04 Jan 2016TL;DR: In this article, the effects of the tubercle amplitude, wavelength, and phase on the wing performance parameters were considered, whereby increasing the amplitude or wavelength not only resulted in these individual parameters to be more effectual, but for the phase to be effectual as well.
Abstract: Prandtl’s lifting-line theory has been implemented to determine the effects of a tubercle’s amplitude and wavelength on the lift coefficient, induced drag coefficient, and the lift-toinduced-drag ratio of a NACA 0021 wing at an angle of attack of 3°, and a Reynolds number of 120,000. In addition, a new tubercle parameter has been introduced; the point along a tubercle that a wing terminates. This parameter has been termed the phase of the tubercles. The phase of the tubercles tended to have the greatest effect on the lift coefficient, induced drag coefficient, and the lift-to-induced-drag ratio, while the wavelength had the least. However, the effects of the tubercle amplitude, wavelength, and phase on the wing performance parameters considered were inter-dependent, whereby increasing the amplitude or wavelength not only resulted in these individual parameters to be more effectual, but for the phase to be more effectual as well. Typically, a particular tubercle geometry that reduced the lift coefficient also reduced the induced drag coefficient, and the lift-to-induced-drag ratio would increase. The lift-to-induced-drag ratio was increase by as much as 7.7% for the considered tubercle geometries.
12 citations