In looking through the list of British Commonwealth Lectures one finds that the great majority deal with the work or problems of a particular country. There are few which deal with the Commonwealth as a whole, the outstanding exception being the remarkable paper on Aviation and the Development of Remote Areas given by H.R.H. the Duke of Edinburgh in 1954.

In this paper an experiment is described in which a detailed study was made of the flow field associated with a slender sharp-edged delta wing which was rolling steadily at zero angle of attack to an air stream. The investigation was made by performing two pressure surveys: first , one of the static pressure acting on the wing’s surface and second by measuring the total-head distribution in the neighbourhood of the wing. From the former the local rolling-moment coefficients, Clp, are evaluated and these are compared with the predictions for attached flow, thus assessing the contributions to the forces acting on the wing which arise as a consequence of the leading-edge separations. The second set of surveys is used to construct a picture of the flow-field details and this is compared with that known to occur on a similar wing when it is set at an angle of attack to the airstream. One interesting finding is that the secondary separation which appears to cause the discrepancy between the theoretical predictions and the measurements made on slender wings at incidence, is absent in this configuration and thus it is concluded that these data could be used for a more meaningful test of the theory.

The problem of maximising the range of a given unpowered, air-launched vehicle is formed as one of Mayer type in the calculus of variations. Eulers’ necessary conditions for the existence of an extremal are stated together with the natural end conditions. The problem reduces to finding the incidence programme which will give the greatest range.

The vehicle is assumed to be an air-to-ground, winged unpowered vehicle flying in an isothermal atmosphere above a flat earth. It is also assumed to be a point mass acted upon by the forces of lift, drag and weight. The acceleration due to gravity is assumed constant.

The fundamental constraints of the problem and the Euler-Lagrange equations are programmed for an automatic digital computer. By considering the Lagrange multipliers involved in the problem a method of search is devised based on finding flight paths with maximum range for specified final velocities. It is shown that this method leads to trajectories which are sufficiently close to the “best” trajectory for most practical purposes.

It is concluded that such a method is practical and is particularly useful in obtaining the optimum incidence programme during the initial portion of the flight path.

Starting from the momentum integral equation an analysis is made of fully-developed flow in a straight pipe. This analysis shows the assumptions implicit in the one-dimensional theory of adiabatic constant-area flow with friction. For conditions of practical interest the approximations associated with the use of the one-dimensional flow theory are shown to be small.

Flow with a developing velocity profile and flow in a bend are then analysed. Introducing approximations revealed in the analysis of fully-developed flow, a simple relation is obtained between the variation of mean flow properties along the duct under incompressible and compressible flow conditions. This relation may be written in the same form as the corresponding relation derived using the one-dimensional flow theory. In a similar manner to one-dimensional flow theory, the relation is readily extended to apply over a series of components of constant cross-sectional area.

The results of the analysis are also presented in terms of static and total pressure loss coefficients. This form of presentation demonstrates that there are appreciable effects of Mach number, on the pressure loss coefficients, where they are often assumed to be small.

The analysis does not enable the variation of the mean flow properties to be calculated ab initio. Its application is to be found in problems where a knowledge of the performance of a component, or series of components, is required under compressible flow conditions, the performance under incompressible flow conditions already being available from theoretical or experimental data.

A comparison of predicted and experimental data for flow in bends and flow in combinations of duct components shows good agreement over much of the subsonic speed regime.

This contribution to the proceedings of the Agricultural Section of the Society is intended: —

• (a) To describe a problem in agricultural logistics which when solved should help developing countries in Asia to increase their food production, especially of rice.

• (b) To suggest that the problem could be solved from the air.

• (c) To offer some layman’s suggestions as to methods by which aircraft and associated installations might be designed and organised to meet the special situation to be found in Asia. From professional advice on these suggestions it is hoped that a workable plan may be devised, and the necessary finance provided from Government or commercial sources to carry out the necessary research and development.

• (d) If a workable plan can be devised it is hoped that one or more of the countries which might benefit would wish to accept any assistance offered and to co-operate in the arrangements necessary.

• (e) While the observations in this paper are believed to be generally applicable to the flat rice-growing monsoonal areas of Asia the ideas have been derived from working experience (for three years) in only two of these countries: Burma and E. Pakistan.

A type of structure for which no general method of analysis appears to be available is that of a curved beam of low torsional strength and stiffness supported by a torque box. This note outlines ways of analysing two simple cases.

The purpose of this note is to report the results of an experimental investigation which was conducted to permit the local mass transfer rate around a sphere to be visualised. The present problem of mass transfer from a sphere had its origin in a study of the evaporation of a water droplet in a superheated steam atmosphere. Because of the small physical size of the droplet and the difficulty of measuring local mass transfer rates from the droplet surface, it was necessary to employ a large scale model to study local transfer rate around a sphere. It was considered that flow visualisation would afford at least a qualitative result of local mass transfer rate. In fluid mechanics studies, the flow visualisation techniques are well known. Such methods include the use of smoke filaments, tufts, or chemical coatings and so forth to provide information about the state of boundary layer over a solid surface, fluid particle paths and state of flow.