Experimental and numerical study of the flight of geese

Abstract

The flight of barnacle geese at airspeeds representing high-speed migrating flight is investigated using experiments and simulations. The experimental part of the work involved the filming of three barnacle geese (Branta Leucopsis) flying at different airspeeds in a wind tunnel. The video footage was analysed in order to extract the wing kinematics. Additional information, such as wing geometry and camber was obtained from a 3D scan of a dried wing. An unsteady vortex lattice method was used to simulate the aerodynamics of the measured flapping motion. The simulations were used in order to successfully reproduce the measured body motion and thus obtain estimates of the aerodynamic forces acting on the wings. It was found that the mean of the wing pitch angle variation with time has the most significant effect on lift while the difference in the durations of the upstroke and downstroke has the major effect on thrust. The power consumed by the aerodynamic forces was also estimated; it was found that increases in aerodynamic power correspond very closely to climbing motion and vice versa. Root-mean-square values of the power range from 100W to 240W. Finally, it was observed that tandem flying can be very expensive for the trailing bird.

Unsteady Lifting Line Theory Using the Wagner Function for the Aerodynamic and Aeroelastic Modeling of 3D Wings

“…The unsteady Vortex Lattice Method (VLM) is used as a reference solution to which the results obtained by the Wagner lifting line approach are to be compared. The particular implementation of the VLM used here is more thoroughly described by Dimitriadis et al [29]. The difference between the solutions obtained from WLL and VLM is quantified using the Normalized Root-Mean-Square Deviation (NRMSD).…”

“…T , reduce the time step to ∆t/2 • otherwise, go to the next time instance t i+1 = t i + ∆t and reset ∆t to its default value Figure 5 plots the variation of the error of Equation (29) with the tolerance Tol used in the Runge-Kutta-Fehlberg algorithm with respect to a reference Tol = 10 −9 . The solid line represents the convergence for a step case and the dashed line the convergence for a sinusoidal oscillation case with a reduced frequency k = 0.3.…”

“…The VLM is more sensitive to the chordwise than the spanwise number of panels [30], so a convergence for the number of chordwise panels is performed. Figure 6 plots the variation of the error of Equation (29) with the number of chordwise panels for a rectangular wing (AR = 6) oscillating around its leading edge with a reduced frequency k = 0.3. The reference number of chordwise panels is j = 100.…”

Vortex Lattice Simulations of Attached and Separated Flows around Flapping Wings

“…The Vortex Lattice model employed for this work is similar to the one used by Dimitriadis et al [20] with one major difference: the drag is calculated using both the Katz and Joukowski approaches, as discussed by Simpson et al [34] and Lambert and Dimitriadis [35]. The VLM method is described in detail in several authoritative publications [29,36].…”

“…Computational cost is quite an important consideration due to the unsteady nature of the flow fields so that lower fidelity approaches can be preferable, at least under attached flow conditions. The Vortex Lattice Method (VLM) has been proposed for modeling flapping flight by several authors [15][16][17][18][19][20]. Ames et al [21] compared predictions from a vortex lattice simulation against experimental measurements for a flapping rigid rectangular wing.…”