The mean flow of an incompressible fluid in a straight suction duct with porous walls is considered and relations between the inflow and the pressure difference required to produce it are established on the basis of an elementary momentum analysis. It is assumed that bom the velocity and the pressure across planes normal to the direction of the mean flow inside the duct are distributed uniformly everywhere and that the effect of obstructions, which do not alter significantly the area of the duct cross section at any position, can be described in terms of losses of total pressure which are proportional to the square of the local speed within the duct. A variety of cases is discussed and it is shown that calculation of the internal pressure is straightforward and in agreement with experiment, at least for the case of a pipe having uniform porosity.

A boundary-layer development was measured on the near of a wing swept at 61°. The measurements approximately followed an external streamline from the minimum pressure to the neighbourhood of the separation line. Unfortunately the flow was found to be surprisingly sensitive to traverse gear interference. Moreover, the constraint imposed by the wind tunnel walls was sufficient to throw grave doubts on the use of the assumption of constant spanwise velocity to compute the external flow behaviour from the measured pressure distribution.

Comparison of the measurements with calculations using the method proposed by Cumpsty and Head showed the growth of streamwise momentum thickness, form parameter and crossflow to be seriously underestimated. However, only a small adjustment to the spanwise velocity outside the boundary layer over the rear of the wing was sufficient to bring the results into tolerable agreement. The necessity for such an adjustment to the spanwise velocity may be plausibly explained by the effect of tunnel constraints.

The historical development and current status of compressive orthotropic stability is reviewed and a concise development of the linear theory for the compressive case is presented. Available test data on orthotropically stiffened cylinders are synthesised and correlated in terms of this theory. The correlation has been used to establish regions in which linear orthotropic theory appears to be valid in terms of currently available test data.

A detailed discussion on the difference between an initial value line and a line characterised by a boundary condition has been presented. Two types of boundaries are described and illustrated. To examine each boundary, several different calculations have been performed for a straight pipe. The results of the numerical calculations are compared with an analytical solution. It is shown that known pressure and velocity at the pipe ends give the most accurate results. Comparisons are also made between several practical types of calculations which give similar findings. The use of time-dependent boundaries can lead to errors as large as 40 per cent in derived results. It is shown that good accuracy can be restored by converting the boundaries into initial value lines. It is concluded that in general no more than one time-dependent boundary should be used in any calculation. Finally it is demonstrated that errors are not revealed by means of pressure diagrams alone.

The Dynamic Relaxation method is used to analyse the post-buckling of flat rectangular plates. Extensive results are obtained for two types of problem in which the transverse edges are unloaded; in one case the transverse edges remain straight, in the other they are free to wave. Comparisons are made with alternative experimental and theoretical results. The potentiality of this approach to post-buckling problems is demonstrated by considering a variable thickness plate with mixed boundary conditions.

The solution to the problem of the loading generated on a two-dimensional thin aerofoil by an incompressible flow whose normal velocity component is of the general form exp [i(λx+/μy — ωt)] is calculated. The method used extends the two-dimensional integral equation solution for the induced vorticity by means of a Chebyshev expansion of part of the kernel function. Thin aerofoil approximations are made throughout, but no collocation procedure, as such, is required.