Aerodynamics of the Cupped Wings during Peregrine Falcon’s Diving Flight

Abstract

During a dive peregrine falcons can reach velocities of more than 320 km/h and makes themselves the fastest animals in the world. The aerodynamic mechanisms involved are not fully understood yet and the search for a conclusive answer to this fact motivates the three-dimensional (3-D) flow study. Especially the cupped wing configuration which is a unique feature of the wing shape in falcon peregrine dive is our focus herein. In particular, the flow in the gap between the main body and the cupped wing is studied to understand how this flow interacts with the body and to what extend it affects the integral forces of lift and drag. Characteristic shapes of the wings while diving are studied with regard to their aerodynamics using computational fluid dynamics (CFD). The results of the numerical simulations via ICEM CFD and OpenFOAM show predominant flow structures around the body surface and in the wake of the falcon model such as a pair of body vortices and tip vortices. The drag for the cupped wing profile is reduced in relation to the configuration of opened wings (without cupped-like profile) while lift is increased. The purpose of this study is primarily the basic research of the aerodynamic mechanisms during the falcon's diving flight. The results could be important for maintaining good maneuverability at high speeds in the aviation sector.

From wing shape to fluid dynamics in the barn owl (Tyto alba)

“…Birds fly over a wide range of speeds by morphing their wings and tail to modulate aerodynamic force production. At the fastest gliding speeds, birds hold their wings in a folded and swept back configuration, and the tail is held in a contracted state to minimise area; as in the stooping postures of hunting birds (Ponitz et al, 2014). With decreasing speed, birds unfold their wings, reduce wing sweep until they spread laterally, but maintain the tail in the same contracted state (Rosen and Hedenström, 2001; Henningson and Hedenström, 2011).…”

Vortices enable the complex aerobatics of peregrine falcons

“…The success of the attack largely depends on the manoeuvrability during the second phase of the stoop, when the bird 1 starts to pull out from the dive, while undergoing two important morphological transformations, namely the cupped-wing shape (C-shape, detail presented in ref. 4 ) and the M-shape (the focus of this manuscript). In C-shape the arms are slighly untucked, creating a cavity between the body and the primary feathers, which are oriented vertically.…”

Investigation of Falcon Dive and Developing Kinematic Approach

“…As per Ponitz et al, the cupped wing configuration is when wings are downward tilted and aimed at adopting a marginal deceleration to adjust its trajectory. [11] On the contrary, the open-cupped wing configuration is an intermediate configuration between the cupped shape and tear drop shape, mainly concerned with control and maneuverability. [11] In order to better understand aerodynamics of these configurations, computational fluid dynamics was performed with the help of ICEM CFD, and Open FOAM.…”

“…[11] On the contrary, the open-cupped wing configuration is an intermediate configuration between the cupped shape and tear drop shape, mainly concerned with control and maneuverability. [11] In order to better understand aerodynamics of these configurations, computational fluid dynamics was performed with the help of ICEM CFD, and Open FOAM. [11] The numerical simulation enabled the calculation of integral forces such as lift and drag using the velocity and pressure data field obtained.…”

“…[11] In order to better understand aerodynamics of these configurations, computational fluid dynamics was performed with the help of ICEM CFD, and Open FOAM. [11] The numerical simulation enabled the calculation of integral forces such as lift and drag using the velocity and pressure data field obtained. [11] These forces were then used to find its corresponding coefficients using Eq.…”