Axial, normal (radial) and tangential turbulence intensity measurements have been carried out in the past in pipe and two-dimensional channel flows, e.g. Refs. 1-9. A similarity in the distribution of these turbulence intensities is observed. They are all minimum at the centreline, increasing steadily as the wall is approached, until they reach some maximum values close to the wall, then they start to decrease as the wall is approached further. Furthermore, the three components of turbulence intensity have been observed to vary in a similar way with the Reynolds number.

On the other hand, the Prandtl mixing length theory assumes that the turbulent fluctuations are proportional to the product of a local mixing length and a velocity gradient. This implies that the turbulence fluctuations are directly proportional to each other. It is, therefore, found worthwhile examining the possibility of a relationship between the turbulence intensities. Smooth pipe and channel flows are chosen for this purpose.

This note describes brief tests made to check a proposed extension to the Royal Aeronautical Society Stressed Skin Data Sheets on stresses and deflections in flat panels subjected to normal pressure. Simple modifications to the test rig, which greatly improved the edge fixing, are also included.

In this paper it is shown how, in an angular contact ball bearing, the motion of a ball depends on the dimensions, loading and speed of the bearing. In general, ball motion in an angular contact bearing differs from the simple motion usually visualised by including oscillatory occurrences, shown here analytically, graphically and visually. These oscillatory occurrences are shown to lead to premature fatigue of the bearing metal, as a function of the speed of rotation, thereby imposing the present limitations on maximum speed and “ life.”

It is further shown that only when the dimensions of an angular contact ball bearing are related in a certain way, a motion is produced in which the oscillatory phenomena are eliminated. These relations are given as functions of loading and speed in a system of equations and limiting conditions (hereafter referred to as “ Relations of the Dimensions ”).

The planar vortex lattice method is extended to the case of wings in small-amplitude oscillations in ideal flow. Vortex rings are used to represent the bound vorticity on the wing and the trailing vorticity in the wake. A modified procedure for solving the unknown vortex strengths gives greater computing efficiency. Comparisons with results reported in the literature show good agreement for the various test cases considered. Convergence with increasing lattice density is uniform.

The Free and damped vibrations of a circular plate with given initial conditions, which is either free or elastically restrained along its outer edge, are discussed using the method developed by Reid and some numerical results are also given.

The vibration of a circular plate has been studied considerably and most of the authors seem to be interested in determining the frequencies of vibration and the nodal patterns. A few investigators have studied the problem of determining the subsequent motion of a thin plate started with some given initial displacement or velocity. Sneddon has attempted this problem, taking into account an approximate boundary condition. Recently Reid has discussed this problem without taking recourse to any approximate boundary condition. He has developed a method of analysis to determine the displacement of a freely vibrating thin circular plate with the given initial conditions, using the norm of the eigen functions.

In 1972 civil sales formed some 30% of the US aerospace industry. Although in 1973 there was a swing back to defence products, civil sales retain an important position. Not surprisingly, aerospace industries without sizeable civil projects on hand, such as Britain's and Canada's, are looking with concern at their future prospects.

Such increasing dependence brings its own problems, for civil sales have been characterised by large fluctuations in the past. Predictions have often been wrong and costly, yet accuracy is a prerequisite of the industry's steady development. The heavy research and development and expenditure involved in a major civil programme necessitates a forecasting horizon of up to a decade.

Today we speak of the quality of life and the need to improve the quality of the environment. The removal of all kinds of pollution from our environment is a laudable aim and for some types of pollution positive action and an awareness of the problem can make improvements with a minimum of cost. However, in the case of most forms of pollution, and this includes noise, improvement in the quality of the environment can only proceed at a price. Thus there is considerable need for phased reductions in pollution and future planning with imposed realistic targets is paramount. In this region of social planning the problem of cost benefit analysis cannot always be applied and pressures are exerted to directing funds for economic gains and combating other pressures in national and international life in directions which lead away from pollution control. Nevertheless improvements to the environment dependent on the supply of finance can only be achieved, all other things being equal, when the economic state of a country is stable and attention of governments is directed with a willingness to achieve what at first sight is a downright impossibility.

In a recent note, Allen has investigated the use of Preston tubes and Clauser charts for determining the skin friction in supersonic, boundary-layer flows. He concluded that the Preston tube was best used in conjunction with the law of the wall of Fenter and Stalmach but that the Baronti and Libby wall law was most suitable for determining local skin friction from velocity profiles; both methods are complex and do not permit the direct use of Clauser charts. The present note presents a simple transformation which permits incompressible Clauser charts to be used for the evaluation of skin friction in supersonic flows; the method is applicable to both adiabatic and nonadiabatic situations. Some conclusions, based on experimental experience, are drawn regarding the determination of skin friction by sub-layer methods.

In Figs. 1 and 2 are shown two cantilevers, one acted on by a force which maintains its direction as the cantilever deflects, and the other acted on by a follower force which remains tangential to the end of the cantilever. It can be shown, by a simple demonstration, that a follower force is non-conservative (see Bolotin), and therefore has the capability, if it exceeds a certain critical magnitude, of causing oscillatory instability. Thus, the follower force system in Fig. 2 can become unstable in the oscillatory sense while the Euler Strut in Fig. 1, being a conservative system, can become only “statically” unstable, i.e. with the strut diverging monotonically from its equilibrium position. The follower force system can, of course, also become statically unstable. The overall stability of this system has been examined by Bolotin and Beck. Herrmann and Bungay have investigated the stability of a system that combined the main characteristics of the two above in any chosen proportion.

Supersonic speeds of flight have brought thermal problems due to the kinetic heating of skin materials. These materials, generally metallic, suffer loss of strength and stiffness with increase in temperature and a knowledge of changes in value of these properties at elevated temperatures is a pre-requisite to a design study. More particularly for stress offices the compressive stress-strain curves are required from which are derived tangent- and secant-moduli used to predict buckling in components. A fixture has therefore been developed for testing under edgewise compression sheet materials up to temperatures of 400 °C.

An established method is used to find the stresses in a square plate pierced by a central circular hole. Although the method is not new, the problem is a practical one which has attracted some interest and for which some excellent experimental results are available.

The general problem of a finite plate containing a circular hole was examined by Sekiya who selected various combinations of the general solutions of the biharmonic equation in polar co-ordinates such that the boundary conditions on the hole were satisfied exactly. The boundary conditions on the sides of the plate were satisfied approximately by collocation. The same approach has recently been suggested by Waters for the particular case of a stress-free hole.

In the past, the Society did much for Lighter-than-Air, through its lectures, most of which I was able to attend. I well remember that anti-airship man, E. F. Spanner, who used to face a basically hostile audience, and the fighting speeches from that great protagonist for airships, the late Captain Boothby.

The first, I think, to give lectures on airships was the late Colonel Waterlow in 1912 and 1913, but I was at Wellington then, and so was not present. Nobody fought harder than he did for airships, and he was very helpful to me when I used to visit the airship station at Wormwood Scrubbs.

The main contribution of psychology to the design of displays up to the present time has been in advising on detailed points of design. It is suggested that there are three areas in which psychology can make a useful contribution; these are

(a) in stating the basic characteristics of the human operator, particularly the working of the perceptual mechanism,

(b) in stating the effect of environmental conditions on performance, and

(c) in assessing the information required and in advising on man's rôle in the system.

A method for the detection of the important modes participating in flutter is presented in this paper. The method is based on energy considerations and is illustrated by numerical examples.