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 computational model for estimating the mechanics of horizontal flapping flight in bats: model description and validation

Abstract: We combine three-dimensional descriptions of the movement patterns of the shoulder, elbow, carpus, third metacarpophalangeal joint and wingtip with a constant-circulation estimation of aerodynamic force to model the wing mechanics of the grey-headed flying fox (Pteropus poliocephalus) in level flight. Once rigorously validated, this computer model can be used to study diverse aspects of flight. In the model, we partitioned the wing into a series of chordwise segments and calculated the magnitude of segmental aerodynamic forces assuming an elliptical, spanwise distribution of circulation at the middle of the downstroke. The lift component of the aerodynamic force is typically an order of magnitude greater than the thrust component. The largest source of drag is induced drag, which is approximately an order of magnitude greater than body form and skin friction drag. Using this model and standard engineering beam theory, we calculate internal reaction forces, moments and stresses at the humeral and radial midshaft during flight. To assess the validity of our model, we compare the model-derived stresses with our previous in vivo empirical measurements of bone strain from P. poliocephalus in free flapping flight. Agreement between bone stresses from the simulation and those calculated from empirical strain measurements is excellent and suggests that the computer model captures a significant portion of the mechanics and aerodynamics of flight in this species.

Ideal Lift Distributions and Flap Angles for Adaptive Wings

Abstract: An approach is presented for determining the optimum flap angles and spanwise loading to suit a given flight condition. Multiple trailing-edge flaps along the span of an adaptive wing are set to either reduce drag in rectilinear flight conditions or to limit the wing bending moment at maneuvering conditions. For reducing drag, the flaps are adjusted to minimize induced drag, while simultaneously enabling the wing sections to operate within their respective low-drag ranges. For limiting wing bending moment, the flaps are used to relieve the loading near the wing tips. An important element of the approach is the decomposition of the flap angles into a distribution that can be used to control the spanwise loading for induced-drag control and a constant flap that can used for profile-drag control. The problem is linearized using the concept of basic and additional lift distributions, which enables the use of standard constrained-minimization formulations. The results for flap-angle distributions for different flight conditions are presented for a planar and a nonplanar wing. Postdesign analysis and aircraft-performance simulations are used to validate the optimum flap-angle distributions determined using the current approach.

Lift-drag and flow structures associated with the "clap and fling" motion

Abstract: The present study focuses on the analysis of the fluid dynamics associated with the flapping motion of finite-thickness wings. A two-dimensional numerical model for one and two-winged “clap and fling” stroke has been developed to probe the aerodynamics of insect flight. The influence of kinematic parameters such as the percentage overlap between translational and rotational phase ξ, the separation between two wings δ and Reynolds numbers Re on the evolvement of lift and drag has been investigated. In addition, the roles of the leading and trailing edge vortices on lift and drag in clap and fling type kinematics are highlighted. Based on a surrogate analysis, the overlap ratio ξ is identified as the most influential parameter in enhancing lift. On the other hand, with increase in separation δ, the reduction in drag is far more dominant than the decrease in lift. With an increase in Re (which ranges between 8 and 128), the mean drag coefficient decreases monotonously, whereas the mean lift coefficient decreases to a minimum and increases thereafter. This behavior of lift generation at higher Re was characterized by the “wing-wake interaction” mechanism which was absent at low Re.