Numerical methods have been developed for the prediction of aerodynamic characteristics of canard wing configurations by considering both attached and separated flow over the canard surface; the flow over the main wing surface is always assumed to be attached. Experimental tests have been conducted in a low speed wind tunnel to compare the theoretical results predicted by the numerical methods. The comparison shows good agreement up to approximately 16° incidence.

Affine transformation and similarity rules has been used to solve the classical bending, buckling, and vibration problems of orthotropic plates. The present work extends these concepts to antisymmetric angle-ply laminated plates by employing a simple transformation, utilising previous material constant definitions by Tsai and Brunelle, and a similarity parameter. With the help of certain defined characteristic and bounded quantities, comprehensive solutions are found to this problem; hence, the curves presented in the text are generic rather than specific. The results indicate that the frequency parameters and buckling coefficients increase with increasing generalised rigidity ratio D* and decrease with increasing generalised Poisson’s ratio ε, and the static deflection coefficients decrease with increasing D* and increase with increasing ε. The results of a reduced set of equations agree with those obtained by previous investigators.

A low-order panel method is presented for the calculation of subsonic or supersonic linear flow about general configurations. The method uses piecewise constant source, doublet and/or vorticity singularities. The internal Dirichlet boundary condition is applied, providing zero perturbation potential inside the configuration. The external Neumann boundary condition may refer to a condition on the outward conormal component of the perturbation velocity (the so-called 'linearised normal mass flux'). However, the program may, if required, proceed to obtain specified conditions on the outward normal component of the perturbation velocity, using an iterative procedure.

Under zero-gravity conditions, the liquid surface in a container has a displaced equilibrium position due to surface tension effects; this depends upon the magnitude of the contact angle to the wall. Free and forced sloshing have been investigated for these conditions. It was found that the natural frequencies of the liquid increases with the contact angle to a maximum value at a contact angle slightly above π/2 and then decreases. This behaviour is not symmetrical within the wetting and non-wetting range. Thus, a completely non-wetting liquid has larger natural frequencies than a completely wetting liquid. It was also found that the sloshing mass of a wetting liquid is considerably larger under zero-gravity than under normal gravity conditions and that a non-wetting liquid exhibits substantially reduced sloshing mass, indicating that the influence of liquids with a small contact angle on the dynamics of a vehicle with liquid containers (with a free liquid surface) may be quite pronounced.

Reference to the few general papers on aircraft antennas which had been published up to 25 years ago shows that the underlying rules of antenna siting were well understood even though there were few theoretical models at the time. The hardware has changed considerably to reflect new environmental requirements and new manufacturing techniques. In this paper, antenna siting rules are reviewed in the light of aircraft developments and the increasing range of airborne radio systems. Some recent solutions to siting problems are discussed together with some thoughts on possible future problems.

Two versions of the Sequential Quadratic Programming technique for constrained optimisation are described and used to solve some minimum weight design calculations for aircraft wings. The problems and the solution methods are described and discussed in some detail: but the main feature of the work is the use of the programming language Ada for writing the necessary software. Some features of the language are illustrated which appear to be valuable for many kinds of numerical computation. In particular, it is also shown that Ada facilitates the calculation of the partial derivatives of function and constraint expressions which are required in optimisation calculations but which are often quite difficult to obtain in practice.

The problem of fracture characterisation of geometrically complex structures is considered. Numerical and experimental strategies are used to evaluate stress intensity factors and elastic fields for cracked thin shell and plate structures. Theoretical analyses, using different order theories, are also performed in order to evaluate stress and energy distributions in the neighbourhood of the crack tip. A geometrically complex strut component is analysed by using a ‘p-convergent’ finite element code based on hierarchic elements and on the high degree of approximating functions. Actual fracture modes, for different crack locations, have been singled out and the elastic fields are compared to those referring to cracked plate and shell structures. An experimental investigation, using the optical method of caustics, has been also performed and stress intensity factors for several crack configurations have been calculated. The numerical investigations have shown the ability of the p-version finite element method to provide accurate computation of local stress values and to quote the convergence of the numerical calculations. The caustics method has confirmed its accuracy for evaluating stress intensity factors, even for complex structures.

The pressure distributions over a 6:1 fineness ratio ogive cylinder model have been obtained over a wide pitch range in the rectilinear flow provided by the CoA 8 ft x 6 ft low speed wind tunnel and the curvilinear motion provided by the CoA Whirling Arm facility. The pressure distributions were integrated first to obtain the local normal-force loading distribution along the body and then the overall normal-force and pitching moment and hence the centre of normal-force.

A comparison of the results showed that the main difference between the aerodynamic characteristics was a considerable positive increase in normal-force loading over the whole of the afterbody in curvilinear motion which varied little with the magnitude or sign of the pitch angle. Some smaller changes were also apparent in the forebody loading characteristics. These changes resulted in the body developing considerably more normal-force and nose-down pitching moment in curvilinear motion than in rectilinear flow with the resultant large rearward movement of the centre of normalforce.

It was found possible to estimate the main features of the loadings, but the theoretical methods available did not predict very well the variations in loading obtained experimentally at the extreme beginning and end of the parallel afterbody.

The method of matched asymptotic expansions is used to calculate the lift for a class of thin aerofoils with highincidence flaps or blunt trailing edges. The analysis is based on smallness of the ratio between the flap length (or trailingedge thickness) and the chord of the main foil. Results are compared with exact solutions for bent plates and for triangular and quadrilateral bodies. A procedure for extension to general trailing-edge configurations, including detached flaps, is outlined.

A finite element method is used for the solution of the full-potential equation in conservation of mass form. The finite element analysis allows the boundary conditions to be treated in simple and exact manner, without the use of a mapping scheme. An efficient finite element computational grid is employed in order to obtain an accurate converged solution. An iterative method is used to solve the full-potential equation. The iteration is in two parts, new values for the velocity potential are found by matrix inversion while the density is not updated, then new values of the density are found from the isentropic relation. The density field is then relaxed using new values for the potential in conjunction with an artificial viscosity. Results are obtained for different types of axisymmetric configurations. Comparison is made with available experimental data and good agreement is found for the pressure coefficient distribution over a suitable blunted cone-cylinder axisymmetric body. Further comparisons with experimental data are required in order to assess the method.

Aircraft longitudinal ride-bumpiness during flight at high speed and low altitude is described in terms of the response to discrete gust patterns. Results are expressed statistically in a form that incorporates data from recent turbulence measurements. Effects of basic airframe parameters and of active controls are illustrated and data from a computer-simulation study are used to confirm the validity of the prediction method.

A unified similitude for super/hypersonic flow has been given for non-slender cones and quasicones with attached shock. The similitude space has been shown to be orthogonal to the bow shock and an accurate scaling law for cone flows of different Mach numbers has been provided. A constant density solution has been obtained which gives simple formulas for shock angle and pressure on a cone. This leads to an axisymmetric shock expansion theory which incorporates the effect of profile curvature of an ogive in inviscid flow or a cone in viscous flow whose boundary layer displacement thickness is known a priori. The hypersonic formulas for pitching moment derivatives of oscillating cones and ogives have been adjusted to extend them to supersonic Mach numbers.

Most organisations predict that the expansion of satellite applications to new areas, such as land mobile communications, will be in a rapid worldwide growth phase up to the end of the century. The geographical and geometrical link properties along with the economic aspects (with the projected saturation of the frequency allocation), have led communications services to consider non-conventional orbits for the near future. This paper presents an analysis of the fundamental problems and a statement on the short-term technical solutions within the particular framework of a general land mobile communication mission. The results of these efforts led the authors to propose the Sycomores concept, which is at least a twin satellite system located on particular inclined elliptical geosynchronous orbits.

Discharge coefficients for annular orifices formed between pistons and a cylindrical bore are reported for twelve pistons having orifice length to gap ratios in the range 12 to 50. Square-edged, radiused and tapered orifices are examined at high fluid pressure differentials with Reynolds number varying in the range 500-4000. The radial gaps were determined by examining the flow for each piston geometry at low Reynolds numbers.

Turbulent incompressible heated round jets in a co-flowing stream are analysed theoretically. The normalised mean excess velocity and temperature profiles, as determined by experiments, can be shown to be well represented by appropriately defined Gaussian error-functions. The resulting solutions of the equations of motion and energy give rise to turbulent diffusivities for momentum and heat that are both functions of the stream and radial coordinates and depend parametrically on the co-flowing stream to jet velocity ratio, λ. When λ approaches zero, the eddy diffusivities become independent of the stream coordinate and a constant turbulent Prandtl number is recovered, just as previous studies have predicted. Analytical expressions are obtained for the jet growth and the centreline decay of velocity and temperature. These growth and decay laws are nonlinear functions of the stream coordinate, and show significant deviation from linearity as λ increases. Finally, it is shown that the analytical results are in fair agreement with measurements of round jets in a co-flowing stream, and correctly predict the parametric dependence of jet growth and centreline decay of velocity and temperature on λ.

Cylindrical arrays subjected to external flow have been the subject of considerable study in recent years. Much of this study is concerned with a solitary cylinder or cylinder arrays involving many cylinders with the same diameters. Common structures however have cylinders with different diameters. For example, in a reactor, there are small diameter cylinders amongst large ones. In this situation, the dynamic behaviour of the cylinders are different from the cylinder arrays of equal diameters. Since the case of a pair of parallel circular cylinders in a cross-flow constitutes the simplest configuration, its study should be of importance in the understanding of more complicated situations. Various modes of oscillations associated with two interfering cylinders may be found in review papers by Zdravkovich. This note presents some laboratory observations of the response of a rigid twodimensional flexibly mounted smooth circular cylinder, with vibrations restricted to a plane normal to the incident flow, as induced by the vicinity of a rigid parallel circular cylinder of different diameter.

The general theory of the stability of equilibrium of discrete conservative systems is reviewed with an eye to implementation in finite element structural analysis. The approach features a natural parameter, such as the applied loading of a system, as the independent variable; all results are thus conveniently established without recourse to any of the artificial parameters advocated by some earlier authors. The criteria for identifying singular (critical) points, which include bifurcation points and limit points, and determining their stability are obtained in simple forms suitable for computation. Numerical results are given for an example problem characteristic of a loaded plate with multiple, stable and unstable, bifurcation points to demonstrate an application of the theory.

A method has been developed for calculating the load distribution, overall forces and moments on a thin wing of arbitrary shape undergoing small amplitude simple harmonic motion in inviscid, incompressible flow. The method is compared with experimental data and other theoretical methods for wings and control surfaces in pitching oscillation and wings going through a sinusoidal vertical gust.