The present state of knowledge on the problem of fatigue failure due to vibrations excited by jet noise is reviewed. It is concluded that it should currently be possible to make reasonable estimates of the stress levels set up in a structure by jet noise but, in general, the resultant fatigue life of the components cannot be estimated with any confidence.

The momentum equation is used to calculate the drag that acts near the tip of a semi-infinite swept-forward wing of constant chord that is at zero incidence to a uniform stream of incompressible, inviscid fluid. The drag is given as a function of wing section and angle of sweep and is shown to be unaffected by shaping the tip. The results may be used to calculate the drag that acts near die centre and the thrusts that act near the tips of a swept-back wing, provided that its aspect ratio is sufficiently great for the regions where the different forces act to be separated. Some results due to Neumark and to Küchemann and Weber suggest that this will be so provided that the aspect ratio is greater than about two. The results are combined with some due to these authors to estimate the spanwise extent of the forces. It is found that this extent decreases as the angle of sweep is increased and that it depends quite markedly on the wing section.

This paper is concerned with the buckling under uniform longitudinal compression of a variety of structures composed of plates whose thickness tapers linearly to zero across the section. Such structures include the angle of Fig. 1, the strut of cruciform section of Fig. 2 and the simply-supported strip of Fig. 3. For given cross-sectional area and overall dimensions (e.g. length of arm) the sections with linearly varying thickness achieve a greater buckling load (assuming that local buckling, rather than Euler buckling, is the criterion) than sections with any other smooth variation of thickness. These particular sections are therefore optimum sections and, even if they may not be used in practice, provide a convenient yardstick for purposes of comparison. The buckling loads are considerably greater than those for the corresponding “constant thickness” sections.

The equations of motion for an isolated laminar viscous vortex at moderate to large Reynolds numbers are linearised, by assuming that both the rotational velocity and the deficit of longitudinal velocity are small compared with that in the free stream. The rotational motion and the longitudinal motion may then be superimposed and solutions are readily obtained for each. If the vortex is generated by a body with profile drag it is predicted that the deficit of longitudinal velocity will be positive, which is in agreement with experimental observation. Further details of the solution and its relation to the flow in real vortices are discussed; and the theory is compared with some measurements in a turbulent vortex.

Previous theories on the surging of axial compressors have been based on a quasi-static theory, whereas a finite rate of growth of the circulation around each blade must occur in practice. An examination of this factor is made in the paper, studying the stability with respect to small changes in speed instead of mass flow as in the normal approach. Effects of capacity are neglected. It is concluded that an instability occurs in the last stage of the compressor, even when that stage is itself unstalled, which could give rise to surge. It has been found necessary to introduce one empirical factor into the analysis but, when this is given a value compatible with other experimental and theoretical evidence, reasonably good agreement with experimental results is obtained.

General expressions are obtained for the stress distribution in a flat plate end-loaded by equal principal stresses and containing a circular hole reinforced by an annular plate. The reinforcement is placed on one side of the plate only so that the other side remains flush. It is shown that the effect of an asymmetrically placed reinforcement is to induce, in the plate and rein-forcement, bending stresses which are not negligible compared with the externally applied direct stress. From particular examples it is found that reinforcements having practical dimensions can give rise to stress concentrations in the same order of magnitude as those in a similarly loaded plate containing an unreinforced hole. For practical purposes, data have been obtained which enable the designer to determine quickly the stress distributions associated with reinforcements and plates having a reasonably wide range of dimensions.