THE FLIGHT OF ALBATROSSES (A COMPUTER SIMULATION)

Abstract

Summary.The equations of motion for gliding flight in a wind gradient have been used to study the way in which the albatross can gain height in non‐powered flight against a purely horizontal wind. It is argued that a type of potential and kinetic energy parameter is convenient for the assessment of climbing performance if the kinetic energy term involves the airspeed rather than the absolute velocity. The gradient with height of this parameter shows a maximum value at a particular climb angle for each speed and wind gradient.Two types of complete flight cycle have been investigated in a logarithmic wind velocity profile having a speed of 15 m/sec at a height of 10 m. The emphasis in the study has been on the possibilities of making progress against the wind. Progress in any other directions is very much easier to achieve.The first cycle is simple and unidirectional with an upwind dive. Although this leads to a fairly rapid progress against the wind it is shown to be impossible without some power input.By contrast, the more usual flight cycle which involves a dive in the downwind direction is completed very easily without loss of flying speed. In fact, by diving steeply, sufficient excess airspeed can be gained to permit a very long final upwind glide at low level. This repasses the starting position and thus gives a slow but definite nett progress against the wind.