JEB desktop wallpaper calendar 2016

JEB desktop wallpaper calendar 2016

Experimental verification of dynamic soaring in albatrosses
G. Sachs, J. Traugott, A. P. Nesterova, F. Bonadonna

SUMMARY

Dynamic soaring is a small-scale flight manoeuvre which is the basis for the extreme flight performance of albatrosses and other large seabirds to travel huge distances in sustained non-flapping flight. As experimental data with sufficient resolution of th ese small-scale movements are not available, knowledge is lacking about dynamic soaring and the physical mechanism of the energy gain of the bird from the wind. With new in-house developments of GPS logging units for recording raw phase observations and of a dedicated mathematical method for postprocessing these measurements, it was possible to determine the small-scale flight manoeuvre with the required high precision. Experimental results from tracking 16 wandering albatrosses (Diomedea exulans) in the southern Indian Ocean show the characteristic pattern of dynamic soaring. This pattern consists of four flight phases comprising a windward climb, an upper curve, a leeward descent and a lower curve, which are continually repeated. It is shown that the primary energy gain from the shear wind is attained in the upper curve where the bird changes the flight direction from windward to leeward. As a result, the upper curve is the characteristic flight phase of dynamic soaring for achieving the energy gain necessary for sustained non-flapping flight.

FOOTNOTES

  • AUTHOR CONTRIBUTIONS

    Conception: G.S. Design: G.S., J.T. and F.B. Execution: J.T. and A.P.N. Interpretation of the findings: G.S. and J.T. Drafting and revising the article: G.S. and J.T.

  • COMPETING INTERESTS

    No competing interests declared.

  • FUNDING

    The authors are grateful to the Institut Polaire Français Paul Emile Victor, which supported this work (IPEV, Program No. 354) – the work was performed according to guidelines established by IPEV and CNRS for the Ethical Treatment of Animals. The authors are also grateful for the support provided by National Science Foundation International Research Fellowship for A.P.N. (no. 0700939).

  • LIST OF SYMBOLS AND ABBREVIATIONS

    CD
    drag coefficient
    CL
    lift coefficient
    Embedded Image
    drag vector
    E
    total energy
    Fflapping
    propulsive force due to flapping
    Fpropulsive
    propulsive force
    g
    acceleration due to gravity
    h
    altitude
    Embedded Image
    lift vector
    Embedded Image
    lift vector component in speed vector plane
    Embedded Image
    lift vector component perpendicular to speed vector plane
    m
    mass
    Pavailable
    available power
    Prequired
    required power
    S
    wing reference area
    t
    time
    tb
    arbitrary time base (1–3)
    tj
    current time
    V
    airspeed
    V*
    speed at the minimum drag-to-lift ratio, (CD/CL)min
    Vinert
    inertial speed
    VPrequired
    speed at minimum power required
    VW
    wind speed
    x
    longitudinal coordinate
    y
    lateral coordinate
    αW
    wind angle
    Δ
    bias
    ρ
    air density
    τ
    time
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