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 first attempt to numerically compute forces on birds in v formation

Abstract: A model for studying the flow forces experienced by cylinders placed in V formation is presented, and an elementary comparison with flocking birds is made. The cylinders are modeled as two-dimensional square bodies exposed to incoming flow at Reynolds number 100. The effects of angle of formation (α), streamwise spacing (Ss), and number of cylinders (N) on parameters such as the coefficient of drag, coefficient of lateral force, and Strouhal number are studied. It is observed that the drag experienced by the cylinders decreases with a decrease in the angle of formation. The leading cylinder experiences the smallest drag, irrespective of the angle. The drag becomes less than the drag on an isolated cylinder at certain angles depending on the position of the cylinder in the formation. The average drag on cylinders in V formation is found to be less than on an isolated cylinder, leading to energy saving when flying in formation. It is also noted that the cylinders experience a substantial lateral force. Study of this simple model may help better understand certain features of flocking birds.

Numerical investigation of the ground effect for a small bird

Abstract: An investigation with computational fluid dynamics of the ground effect on a small bird revealed quantitatively the obstruction of the vortex expansion resulting from the presence of the ground at varied distance. Preceding authors focused mainly on the bird’s wings, generally neglecting the bird’s body; we discuss specifically the distinction of the aerodynamic effect between cases with and without the presence of the bird’s body. The results of simulation show that, considering only two wings, for a distance between the wing model and the ground smaller than a semi-span, the smaller is the ground clearance, the more significant is the ground effect. At clearance 0.37 times a semi-span, the drag is decreased 11, and the lift is increased 5.6. The ground effect for an intact bird model composed of both wings and body is less effective than that for a simplified model with body omitted, because a suction was observed on the lower surface of the intact bird’s trunk at clearance 0.37 times a semi-span; for this reason the intact bird model benefits less from the ground effect than the model with body excluded, but increased lift and decreased drag remain observable. This research treating the ground effect on a gliding bird reveals the importance of the presence of the bird’s body in both computational and experimental models.

Impact of Airfoil Profile on the Supersonic Aerodynamics of Delta Wings

Abstract: A nonlinear flow model was employed to predict the flowfield, pressure and force data for delta wings at supersonic speeds. The goal of the study was to investigate the influence the airfoil profiles has on the wing aerodynamics. The analysis covers wing aspect ratios from 0.5-3.0 with leading edge sweep of 0.5-4.0 on diamond, circular arc and NACA modified 4-digit airfoils. Nonlinear aerodynamics are approximated with nonlinear zero-lift wave drag curves, yielding results significantly different from those obtained from linear calculations. The analytical technique, useful in preliminary design studies, indicates in all cases that 90 percent of wave drag is generated at the wing apex and trailing edge.