The use of finite element analysis in the modelling of an unloaded countersunk hole revealed that there is a consistent relationship between the maximum stress concentration factor and the design parameters of the hole — countersunk depth, edge distance, t/d ratio and countersunk angle. It has been shown that countersunk depth and edge distance have a strong influence on the Kt value while the t/d ratio has a lesser effect. Variation of countersunk angles between 90° and 110° was found to have a negligible influence on the maximum Kt values.

It has also been shown that normalising the stress concentration factors of a countersunk hole by dividing the Ktvalues at various countersunk depths by the Ktvalues for a plain hole of similar configuration, enables the stress concentration factors in a countersunk hole to be determined from values in a plain hole. This is very useful since extensive work had been done on stress concentration factors for a plain hole and data are therefore more commonly available.

The feasibility of mechanical flapping-wing flight has been studied by analyses and experiments. The key results from this work include the development of an efficient wing with unique features for twisting and lift balance, as well as a lightweight and reliable drive mechanism. These were incorporated into a radio-controlled, engine-powered, flapping-wing aeroplane (ornithopter), whose flight tests have been the proof-of-concept focus of this research. In September 1991, this aircraft achieved successful sustained flights, demonstrating the practicability of this particular solution for mechanical flapping-wing flight.

Self-preserving turbulent flows in the farfield of binary gas jets in an arbitrary stream are investigated. The governing equations solved are valid for jet flows only and are not applicable to wake flows where a linearised set of boundary layer equations are more appropriate. Gaussian error-functions are assumed for the mean excess velocity and mass fraction distributions. Thus formulated, the eddy diffusivities for momentum and mass are evaluated by solving the governing equations and are shown to vary across and along the jet. A condition is imposed on the eddy momentum diffusivity so that it correctly approaches the limiting behaviour for the case of an incompressible free round jet. This condition gives rise to an auxiliary equation for the determination of the decay of centreline properties and jet growth. The new and more general auxiliary equation is shown to model fluid entrainment and to reduce correctly to previous equations derived for the special cases of free gas jets and incompressible heated jets in a co-flowing stream. Thus deduced, the new auxiliary equation is solved together with other conservation equations to yield a set of growth rate and decay laws. The derived growth rate and decay laws correctly approach the various laws derived earlier for different special cases and correlate well with experimental measurements reported in the literature. The present solutions also represent solutions for compressible jets in a general stream where the pressure field is constant. Finally, this approach of analysing the self-preserving mean jet flow is also applicable to the study of wake flows where the linearised boundary-layer equations are solved.

Interpreting test data or a mathematical function is often aided by plotting results in the form of contours. Many routines are available to accomplish this, but if a qualitative survey of the data is sufficient then a simple method can be employed using the basic colour screen graphics facilities found on personal computers. The principles of the method are described in this note.

To form a set of contours a base area of the function plane must be defined and the method uses the screen as this base area.