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.

Reduced drag airfoil platforms

Abstract: A flow directing apparatus for use in an axial flow turbomachine is disclosed. Techniques for reducing aerodynamic drag along the walls of the flow directing apparatus are developed. In one embodiment, rotor blades have multiplanar platform surfaces which reduce aerodynamic drag pressure losses at the interface between each blade platform and the adjacent structure.

Numerical investigation of air jets for dynamic stall control on the OA209 airfoil

Abstract: The design and numerical investigation of constant blowing air jets as fluidic control devices for helicopter dynamic stall control is described. Prospective control devices were first investigated using 3D RANS computations to identify effective configurations and reject ineffective configurations. Following this, URANS investigations on the dynamically pitching OA209 airfoil verified that configurations had been selected which reduced the peaks in pitching moment and drag while preserving at least the mean lift and drag from the clean wing. Two configurations using jets at 10% chord on the airfoil top were identified, and one configuration using a tangential slot at 10% chord on the airfoil top, with each configuration evaluated for two jet total pressures. For the best configuration, a reduction in the pitching moment peak of 85% and in the drag peak of 78% were observed, together with a 42% reduction in the mean drag over the unsteady pitching cycle.

Reduction of wave drag by antisymmetric arrangement of wings and bodies.

Abstract: The wave interference effects for bodies or wings in a mirror-symmetric arrangement, and in an antisymmetric arrangement are discussed. It is shown that while in the case of a mirror-symmetric arrangement large adverse interference effects can be observed, antisymmetric arrangements provide comparatively much smaller wave drags. The single continuous wing panels also adapt themselves more readily to varying angles of obliquity, and hence, to varying flight speeds. A detailed review is presented of the previous work on the aerodynamic properties and flight stability of oblique elliptic wing combinations. A possible mode of application of these combinations to transport aircraft operating at moderate supersonic speeds is suggested.

Multidisciplinary optimization of transonic wing design based on evolutionary algorithms coupled with cfd solver

Abstract: Evolutionary Algorithms (EAs) were applied to multidisciplinary transonic wing design optimizations. Aerodynamic performances of the design candidates were evaluated by using the three-dimensional compressive Navier-Stokes equations to guarantee an accurate model of the flow field. The wing structure is modeled on a box-beam to estimate the wing thickness and wing weight. To overcome enormous computational time necessary for the optimization, the computation was parallelized on Numerical Wind Tunnel at NAL in Japan and NEC SX-4 computers at Computer Center of Tohoku University in Japan. First, a singleobjective wing design optimization was demonstrated by maximizing L/D with a structural constraint using a real-coded Adaptive Range Genetic Algorithm (ARGA). Because the structural constraint imposed a tradeoff between minimizations of the induced drag and the wave drag, the present ARGA found a compromised but reasonable design. Then, a multiobjective wing design optimization is performed by minimizing both drag and weight with a constraint on CL using a Multiobjective Evolutionary Algorithm (MOEA). Due to the tradeoff between minimization of aerodynamic drag and minimization of weight of wing structure, the solution to this problem is not a single point but a set of compromised designs. The present MOEA successfully captured these solutions that revealed the tradeoff information. These results showed that EAs were promising approach to multidisciplinary optimization problems.

Spatially distributed control for optimal drag reduction of the flow past a circular cylinder

Abstract: We report high drag reduction in direct numerical simulations of controlled flows past circular cylinders at Reynolds numbers of 300 and 1000. The flow is controlled by the azimuthal component of the tangential velocity of the cylinder surface. Starting from a spanwise-uniform velocity profile that leads to high drag reduction, the optimization procedure identifies, for the same energy input, spanwise-varying velocity profiles that lead to higher drag reduction. The three-dimensional variations of the velocity field, corresponding to modes A and B of three-dimensional wake instabilities, are largely responsible for this drag reduction. The spanwise wall velocity variations introduce streamwise vortex braids in the wake that are responsible for reducing the drag induced by the primary spanwise vortices shed by the cylinder. The results demonstrate that extending two-dimensional controllers to three-dimensional flows is not optimal as three-dimensional control strategies can lead efficiently to higher drag reduction.