The introduction of an interference-fit pin in a circular hole in a flat plate is found to result in a reduction in the stress concentration factor at the hole boundary under tension applied to the plate. The S.C.F. decreases rapidly with increase in the ratio of interference stress to applied tension, and decreases also with increase in the ratio of hole diameter to width of plate. Very little difference in the S.C.F. is found for different ratios of Young's modulus of pin and plate.

A general dynamic model of the hang glider is applied to the analysis of response to control. The transfer functions of the glider to the longitudinal and lateral controls are formulated and some significant results, in terms of frequency response are presented and discussed. The relevant effects of the unsteady aerodynamics on the dynamics of the system are shown and the characteristics of poor lateral control are confirmed as observed in flight.

This note reports tests in a shock tunnel in which a fully integrated scramjet configuration produced net thrust. The experiments not only showed that impulse facilities can be used for assessing thrust performance, but also were a demonstration of the application of a new technique(1) to the measurement of thrust on scramjet configurations in shock tunnels. These two developments are of significance because scramjets are expected to operate at speeds well in excess of 2 km/s, and shock tunnels offer a means of generating high Mach number flows at such speeds.

The contemporary approach to helicopter mathematical modelling in simulation for handling qualities applications is to represent each blade individually. This allows incorporation of effects not possible with a multiblade disc representation of the rotor system. This paper addresses the validation of such a model, which is uniquely performed for large amplitude manoeuvres, using a recently-developed approach to inverse simulation. The method is reviewed in the context of model validation, and comparisons between simulation and actual data are presented for a Puma helicopter executing sidestep manoeuvres in low-speed flight. The focus for interpreting the results is in the area of wake modelling. It is concluded that further developments are necessary in this area if helicopter flight mechanics models are to be used in simulation of role-related flight.

In this paper, we proposed a simple approach to analyse the efficiency and propulsive characteristics of the high-altitude propeller in accordance to the Vortex Lattice Lifting line Method (VLM) theory, which is commonly used in preliminary design and parametric studies of propeller propulsion. The Computational Fluid Dynamics (CFD) method was used to obtain aerofoil aerodynamic data. The optimal pitch angle and propeller blade chord length (along the radial direction) can be calculated using the information from the database. The propeller wake model sees helical slipstreams applied to both lightly and moderately loaded propellers. The proposed method is capable of identifying the optimal efficiency through varying the number of propeller blades, radius and the rotational speed. The relationship between the optimal efficiency and design parameters is then established. This method was verified using CFD calculations.

This paper presents a semi-empirical theoretical model for calculating the effect of nose bluntness on the stability derivatives of oscillating slender cones at hypersonic Mach numbers. It is based on a hybrid blast wave analogy/shock-expansion flow model and is used to obtain closed form analytic expressions for the derivatives for oscillating slender cones. Two models based on zero thickness and finite thickness entropy layers are proposed which are seen to be appropriate to the cases of very small and large nose bluntnesses, respectively. The results are compared with new and existing experimental data and with the predictions of previous theoretical methods.

Usually a fixed pitch propeller is designed to be optimal at cruise speeds. Thus the efficiency is quite low at takeoff or low speeds, as well as during other flight regimes. The present paper shows that by introducing a flexible element into the blade root, the propeller efficiency can be improved over a wide range of velocities. The flexible element reacts to root flap or torsion moments by changing the blade pitch at the root. The root flexibility and the pitch angles at the root at zero loads are chosen such that efficiency will increase during problematic regimes without decreasing the propeller thrust. In the case of straight blades the torsional moment at the root is too small to be used. In the case of swept blades this moment component is significantly increased and can contribute to the design of an optimal aeroelastically adaptive propeller.

A series of advanced aerofoil sections suitable for aircraft propellers has been developed. The sections combine advanced supercritical now characteristics with good low-speed performance and are also directly applicable to other rotating aerodynamic machinery, such as low-solidity ducted fans, windmills, etc. The work has focused initially on propeller sections of around 6 per cent thickness/chord ratio, typical of the fundamental blade station where peak loading is usually carried (0.7 × radius). The complete section family covers a wide range of thickness/chord ratios, from 3 per cent to over 20 per cent. The profiles are defined by mathematical formulae and distort with thickness to achieve a shape having optimum performance characteristics at the flow conditions expected for that thickness. A subset of the family is defined for higher Mach number penetration, up to near sonic values. Practical applications of the new sections have shown notable gains.

Natural frequencies of free flexural vibration of rectangular plates may, in many cases, be considerably increased by attaching to the plate one or more elastic stiffening ribs parallel to one edge, or by casting or machining the plate and stiffeners integrally.

Hoppmann has determined by a semi-empirical method the natural frequencies of an integrally stiffened simply-supported square plate, using the concept of a homogeneous orthotropic plate of uniform thickness having elastic compliances which are equivalent to those of the stiffened plate. Filippov has obtained the exact solution for the fundamental frequency of a simply-supported square plate having a number of equally spaced stiffeners and has considered the effect of point loads applied to the stiffeners in a direction perpendicular to the plane of the plate.

In recent years a number of authors have analysed the bending of clamped skew plates under uniform pressure. Many of these solutions are very approximate. Favre and Dorman adopted the Ritz method and their expressions for displacement are restrictive. Based on the generalised method postulated by Lardy, Mirsky has presented a solution which involves considerable algebraic and arithmetic work. Komatsu's paper contains a solution using conformal mapping. Quinlan has given a powerful method to solve skew plate problems involving different boundary conditions and various types of loadings, but no numerical work has been done.

The components of an aeroengine gas-turbine combustor have to perform multiple tasks – control of external and internal air distribution, fuel injector feed, fuel/air atomisation, evaporation, and mixing, flame stabilisation, wall cooling, etc. The ‘rich-burn’ concept has achieved great success in optimising combustion efficiency, combustor life, and operational stability over the whole engine cycle. This paper first illustrates the crucial role of aerodynamic processes in achieving these performance goals. Next, the extra aerodynamic challenges of the ‘lean-burn’ injectors required to meet the ever more stringent NOx emissions regulations are introduced, demonstrating that a new multi-disciplinary and ‘whole system’ approach is required. For example, high swirl causes complex unsteady injector aerodynamics; the threat of thermo-acoustic instabilities means both aerodynamic and aeroacoustic characteristics of injectors and other air admission features must be considered; and high injector mass flow means potentially strong compressor/combustor and combustor/turbine coupling. The paper illustrates how research at Loughborough University, based on complementary use of advanced experimental and computational methods, and applied to both isolated sub-components and fully annular combustion systems, has improved understanding and identified novel ideas for combustion system design.

Comparisons are made between some measurements of skin friction and heat transfer over five axisymmetric bodies and the predictions of a simple theory. The development of the theory is outlined and explicit expressions obtained for all the gross turbulent boundary-layer characteristics (δ*,θ,H,Cf and St).

Recent advances in two lifting surface methods are reported. The present subsonic constant pressure method improves upon the program robustness of the doublet lattice method. The present unified supersonic-hypersonic method extends the range of applicability of lifting surface theory to the Newtonian limit. Based on a uniformly-valid series formulation, the method accurately approximates the non-linear thickness effect, whereas this effect is neglected by the linear theory and overestimated by piston theory. In fact, the present results generally agree well with the trends of several Euler solutions. Among other findings, cases computed by the unified method confirm that the effect of thickness is to reduce the supersonic flutter speed.

A simple technique is proposed that allows the definition of the geometry and characteristics of an air-jet vortex generator to be defined, using the system requirements in practical design. Typically, the aircraft designer is concerned with the mass flow-rate and air pressure requirements of any pneumatic system for inclusion to an airframe. These parameters are not congruent with those for air-jet vortex generator aerodynamic design, and therefore, some tool is required to bridge the gap.

Such a tool is proposed, based on empirical methods for the prediction of air-jet vortex generator behaviour. The technique allows the comparison of the vortex strength, and the system inputs (the jet mass flow-rate and the air-jet plenum pressure) for the air-jet, for a range of jet nozzle diameters and jet velocity ratios. Through this comparison, the optimum air-jet design can be reached for a given system input.

Recent work by Tsitas and Kingston(1) has demonstrated that an 8kg 6U CubeSat can be designed to perform Earth observation missions equivalent to those of 50-150kg microsatellites. Their design is reviewed and its commercial potential is compared to the 156kg RapidEye spacecraft. Three other commercial applications of this design are described. These are: a standard spacecraft for space scientists and astronomers; the spacecraft component of an N nation 5 spectral band disaster monitoring constellation and a night imaging satellite. Nanosatellites should now be considered for commercial missions previously thought to require microsatellites.

This paper aims to demonstrate the viability of using the large eddy simulation (LES) CFD methodology to model a representative, complete STOVL aircraft geometry at touch down. The flowfield beneath such a jet-borne vertical landing aircraft is inherently unsteady. Hence, it is argued in the present work that the LES technique is the most suitable tool to predict both the mean flow and unsteady fluctuations, and, with further development and validation testing, this approach could be a replacement, and certainly a complementary aid, to expensive rig programmes. The numerical method uses a compressible solver on a mixed element unstructured mesh. Examination of instantaneous flowfield predictions from these LES calculations indicate close similarity with many flow features identified from ground effect flow visualisations, which are well known to be difficult to model using RANS-based CFD. Whilst significant further work needs to be carried out, these calculations show that LES could be a practical tool to model, for example, Hot Gas Ingestion for the Joint Strike Fighter aircraft.

The drag of an aerofoil is often conveniently measured with reasonable accuracy by traversing pitot and static tubes across the wake of the aerofoil and calculating the drag from either the analysis of Betz or that of Jones.

A simulation study was conducted in order to investigate the influence of vortex deformation on wake encounter characteristics. Wake vortices tend to be strongly deformed during the decay process, depending on the atmospheric conditions in terms of turbulence and thermal stratification. For quantification of the influence of vortex deformation, encounters of an aircraft of the ‘Medium’ category behind a generator aircraft of the ‘Heavy’ category were simulated with straight vortices and with realistically deformed vortices derived from large-eddy simulations. All relevant parameters that influence the encounter characteristics, such as encounter angles and positions, were varied within a wide range. In order to cover all kinds of vortex deformation, encounters with different vortex ages from 16-136 seconds were simulated. Hence, all relevant phases during the vortex decay from nearly straight and wavy vortices to vortex rings were considered.

The parameter variation study revealed that on average the impact on the encountering aircraft is less with deformed vortices than with straight vortices of comparable strength. Especially with vortex rings, the encountering aircraft is exposed to a much smaller impact. However, the results also show a larger aircraft response during encounters with wavy vortices just prior to vortex linking. The maximum aircraft response with wavy vortices is stronger than with straight vortices of comparable strength. Also, the strongest encounters occur under greater encounter angles with deformed vortices than with straight ones.

The development of the non-linear equations of motion for the hang glider from first principles is described, including the complex geometry of control by pilot ‘weight shift’. By making appropriate assumptions the linearised small perturbation equations are derived for the purposes of stability and control analysis. The mathematical development shows that control is effected not by pilot weight shift, but by centre of gravity shift and that lateral-directional control by this means is weak, and is accompanied by significant instantaneous adverse response.

The development of a comprehensive semi-empirical mathematical model of the flexible wing aerodynamics is described. In particular, the modelling attempts to quantify camber and twist dependencies. The performance of the model is shown to compare satisfactorily with measured hang glider wing data obtained in earlier full scale experiments. The mathematical aerodynamic model is then used to estimate the hang glider stability and control derivatives over the speed envelope for substitution into the linearised equations of motion.

Solution of the equations of motion is illustrated and the flight dynamics of the typical hang glider are described. In particular, the dynamic stability properties are very similar to those of a conventional aeroplane, but the predicted lateral directional stability margins are significantly larger. The depth of mathematical modelling employed enables the differences to be explained satisfactorily. The unique control properties of the hang glider are described in some detail. Pitch and roll control of the hang glider is an aerodynamic phenomenon and results from the pilot adjusting his position relative to the wing in order to generate out of trim aerodynamic control moments about the centre of gravity. Maximum control moments are limited by hang glider geometry which is dependent on the length of the pilot‘s arm. The pilot does not generate control moments directly by shifting his weight relative to the wing. The modelling thus described would seem to give a plausible description of the flight dynamics of the hang glider.

It was pointed out in ref. 1 that various interpolation techniques could be used to develop elements (for the matrix displacement method) of increasingly more complex characteristics both as far as geometry and specification of strain are concerned. A number of authors have examined this problem in detail and attention is drawn to the excellent work of Bogner, Fox and Schmit on plate elements, and to the elegant paper by Pestel. Over a number of years the ISD at the University of Stuttgart has investigated the application of interpolation functions and has developed within the ASKA language a number of corresponding elements.