The lecture recalls great Manchester traditions in the mechanics of fluids and in related areas of mathematics which were brilliantly renewed from 1945 onwards through Sydney Goldstein’s work as Beyer Professor of Applied Mathematics. Goldstein brought to this important task not only his own personal distinction in those fields but also his great experience in leading interacting groups working in experimental and theoretical fluid dynamics with largely aeronautical objectives. The University has continued strongly to maintain these traditions.

The lecture celebrates also two fine pieces of research where gifted biologists have successfully used certain key mathematical ideas and methods in the mechanics of fluids to solve problems of importance in the field of animal locomotion. The first example is the work of C. J. Pennycuick, J. M. V. Rayner and G. R. Spedding in determining the character of the vortex wake behind a steadily moving bird in horizontal flapping flight. Typically, this takes the form of a “concertina wake” of fluctuating width but approximately constant circulation, exerting forces which are greater in the downstroke (which sheds a wide wake) and less in the upstroke (which sheds a narrower wake). Some notable advantages of the concertina wake are indicated.

Finally, work by Sir Eric Denton, Sir John Gray and Dr J. H. S. Blaxter on schooling behaviour in herrings and other clupeoid fishes is described. These fishes’ mechanisms for advantageously maintaining well coordinated motion of the school as a whole depend not only on eye vision but also on certain specialised organs admirably fitted to the sensing of hydrodynamic pressure fields (associated with the motions of other fishes) and of their lateral and longitudinal gradients.

Aspects of numerical simulation of aircraft program flight along a predetermined trajectory are presented. An emphasis is laid on the problem of describing the required trajectory by means of a succession of defined points. A spline function method is used for interpolation and smoothing routines. Some numerical illustrations of aircraft trajectory flight simulation (only planar motion) are demonstrated and discussed.

Kites are currently used in a number of applications (anemometry, aerial platform, traction), but very little information is available for the systematic design of kite systems. An experimental technique based on an instrumented tether for single-line kites is described. This was used to measure the performance of a variety of single-line kites. The analysis techniques are briefly outlined, and incorporate allowances for kite unsteadiness, the displacement of the kite from the anemometers, extrapolation of the line tension from the tether to the kite, and the kite’s velocity relative to the ground. The results are correlated with aspects of kite design, and specific recommendations for kite applications are made.

Numerical methods have been developed to analyse incompressible viscous flows past three dimensional wings with deflected flap using viscous-inviscid interaction techniques. By using a surface transpiration technique, a panel method for external potential flow calculation is combined with a boundary-layer calculation based on an integral method. For the clean wing case, both three dimensional boundary layer corrections and two dimensional boundary layer corrections are applied in a strip theory sense and compared with experimental results in the literature. It is found that for wings with moderate aspect ratio and sweep angle, viscous corrections at low incidences by the two methods are of the same order. Based on this observation, a two dimensional boundary layer correction method (strip theory sense), including the wake-boundary layer interaction, is developed for the case of wings with a deflected flap of similar planform. Experiments have been conducted to assess the accuracy of the calculation methods for wings with deflected flap; comparison between the experimental and predicted results is encouraging.

Among the experimenters listed in ‘A Directory of Heavier-Than-Air Flying Machines in Western Europe, 850 BC-AD 1783’, was the name of Charles Bernouin, a surgeon of Grenoble, who was said to have flown from a high tower in Regensburg on 15 January 1673. A colleague in Germany has recently sent me two broadsheets, published soon after the event, which show that Bernouin, who has often been mentioned in histories of aviation, should be removed and placed in the ‘List of Rejected Items.’