This series of lectures recalls the achievements of that outstanding pioneer of rotary wing flight Juan de la Cierva. At around the age of 23, he began to develop the concept of improved safety in flying machines, and included in his studies the concept of the helicopter. Having carried out many tests of various possible configurations, he discarded the concept of true helicopter flight as not being achievable with the then current state-of-the-art.

However, he became convinced that his basic objectives of short takeoff and landing, and safe low speed flight could be achieved by replacing the wing of a conventional aircraft with an autorotating rotor.

Four flow cases are calculated using a boundary layer method with five turbulence models. The Johnson-King model, in particular, is modified and two variant forms are used in the present work. The variant forms involve an anisotropic form of three-dimensional eddy viscosity formulations and a modification in the outer viscosity expression. It is found that the Johnson-King model generally performs very well as compared to the others, and the variant forms provide further improvement in most cases.

A “dual-time” method for solving the three-dimensional Euler equations describing the compressible flow about wings undergoing arbitrary motions and deformations is presented. A finite-volume formulation is chosen where the volumes distort as the wing moves or deforms. Independent motion of the inner and outer boundaries of the grid is permitted with a sequence of grids generated using transfinite interpolation.

An implicit real-time discretisation is used, and the equations are integrated in a fictitious pseudo time. This approach allows the real-time step to be chosen on the basis of accuracy rather than stability. It also permits the acceleration techniques commonly used to speed up steady flow calculations to be used when marching in pseudo time, without compromising real-time accuracy. A two-dimensional version of the method has also been developed and results for both two and three-dimensional transonic flows are presented and compared with experimental data where available.

A computational procedure has been developed in order to predict aerodynamic interference between lifting surfaces, and to devise configurations which best meet given aerodynamic requirements. The procedure, which couples an aerodynamic solver with a numerical optimisation routine, is useful in the preliminary design of aircraft. The essential features of the aerodynamic code and of the optimisation routine are described, along with the coupling criteria. Some of the most significant predictions obtained in induced-drag minimisation for wing-tail and canard configurations are described and discussed.

The regional air transport industry is slowly emerging from the ravages of a prolonged structural recession. Long term survival in an industry which has traditionally traded in one of the world's most aggressive market places, will impose enormous demands upon everyone involved. Those regional aircraft manufacturers and operators who are brave enough to take advantage of emerging technologies, adjust to new processes and develop highlyskilled and motivated people will be best equipped to meet the global demands of the marketplace in an ever-changing world.

The actions and achievements of Avro International Aerospace, a division of British Aerospace, with its Regional Avroliner family of aircraft provides an example through which to identify the key components in this process. The challenges facing the regional aircraft industry are identified, together with the resulting business opportunities and the significance of Government support, in order to draw appropriate conclusions with respect to the likely future of the industry.

An improved version (HLLC) of the Harten, Lax, van Leer Riemann solver (HLL) for the steady supersonic Euler equations is presented. Unlike the HLL, the HLLC version admits the presence of the slip line in the structure of the solution. This leads to enhanced resolution of computed slip lines by Godunov type methods. We assess the HLLC solver in the context of the first order Godunov method and the second order weighted average flux method (WAF). It is shown that the improvement embodied in the HLLC solver over the HLL solver is virtually equivalent to incorporating the exact Riemann solver.

An experimental study investigating the aerodynamic characteristics of generic delta wing-body combinations up to high angles of attack was carried out at a subsonic Mach number. Three delta wings having sharp leading edges and sweep angles of 50°, 60° and 70° were tested with two forebody configurations providing a variation of the nose fineness ratio. Measurements made included six-component forces and moments, limited static pressures on the wing lee-side and surface flow visualisation studies. The results showed symmetric flow features up to an incidence of about 25°, beyond which significant asymmetry was evident due to wing vortex breakdown, forebody vortex asymmetry or both. At higher incidence, varying degrees of forebody-wing vortex interaction effects were seen in the mean loads, which depended on the wing sweep and the nose fineness ratio. The vortex breakdown on these wings was found to be a gradual process, as implied by the wing pressures and the mean aerodynamic loads. Effects of forebody vortex asymmetry on the wing-body aerodynamics have also been assessed. Comparison of Datcom estimates with experimental data of longitudinal aerodynamic characteristics on all three wing-body combinations indicated good agreement in the symmetric flow regime.

Passive boundary layer control experiments were conducted on a small supersonic sidewall intake at a Mach number of 1·46 to study the possibility of controlling and improving the intake performance by such a control. The passive control configurations tested included a suction slot in the intake duct located down stream of the shock system (1) connected by a breather passage to a narrow tangential injection slot upstream of the intake and (2) vented to a location where the pressure is free stream static pressure and well away from the inlet of the intake. The results of the experiments showed, that for a supersonic intake, passive control can control the pre-entry shock position, reduce the shock interaction losses and improve the overall pressure recovery.

This paper presents the results of an experimental investigation into the characteristics of boundary layer transition to turbulence in hypervelocity air flows. A series of experiments was conducted using a flat plate model, equipped with static pressure and thin film heat transfer transducers, in a free piston shock tunnel. Transition was observed in the stagnation enthalpy range of 2·35 to 19·2 MJ/kg. The transition Reynolds number correlates well with the unit Reynolds number through a simple empirical relation. The influences of Mach number, pressure and wall cooling are examined. The measured heat transfer rates in laminar and turbulent regions are compared with empirical predictions. Freestream disturbances of the test flow were also measured and analysed.

A comparison between Full Potential and Euler numerical solutions for 2D transonic unsteady flow is presented. The pros and cons of the potential model are discussed and the main features of both computational methods are summarised. The comparison is done for a Naca 0012 aerofoil oscillating in pitch at a freestream Mach number ranging from 0·755 to 0·825, in order to investigate the limit of application of the potential approximation in an unsteady flow.

A numerical technique for the stability analysis of linear mechanical dynamic systems with periodically varying parameters is proposed. The technique is based on representation of the solution vector in terms of Chebyshev polynomials defined over the principal period. Two formulations have been presented. The first formulation is suitable for systems described by state space equations, while the second can be applied directly to a set of second order equations with periodically varying mass, damping and stiffness matrices. As an illustrative example, the flap-lag stability of a multi-bladed rotor is examined. The numerical accuracy and efficiency of the proposed technique is compared with standard numerical codes based on Runge-Kutta, Adams-Moulton and Gear algorithms. The results indicate that the suggested approach is by far the most efficient one, particularly for systems with larger dimensions.

This paper is part of a DLR research programme to develop a three-dimensional Euler code for the calculation of unsteady flow fields around helicopter rotors in forward flight. The present research provides a code for the solution of Euler equations around aerofoils in arbitrary unsteady motion. The aerofoil is considered rigid in motion, and an O-grid system fixed to the moving aerofoil is generated once for all flow cases. Jameson's finite volume method using Runge-Kutta time stepping schemes to solve Euler equations for steady flow is extended to unsteady flow. The essential steps of this paper are the determination of inviscid governing equations in integral form for the control volume varying with time in general, and its application to the case in which the control volume is rigid with motion. The implementation of an implicit residual averaging with variable coefficients allows the CFL number to be increased to about 60. The general description of the code, which includes the discussions of grid system, grid fineness, farfield distance, artificial dissipation, and CFL number, is given. Code validation is investigated by comparing results with those of other numerical methods, as well as with experimental results of an Onera two-bladed rotor in non-lifting flight. Some numerical examples other than periodic motion, such as angle-of-attack variation, Mach number variation, and development of pitching oscillation from steady state, are given in this paper.

The effects of windtunnel constraint during low speed unsteady aerodynamic experiments are assessed by comparing the data from two Naca 0015 models, one with a chord length of half the other. Ramp-up and ramp-down tests are considered, to distinguish between the effects of constraint upon separation and attachment. The unsteady separation process measured in terms of the normal force, pitching moment and stall vortex convection speed, is virtually unaffected by the difference in constraint between the two models, whereas the attachment process, assessed in terms of the normal force response and attachment behaviour, is sensitive to the size of the model.

A hybrid integral equation finite volume scheme has been developed for the calculation of transonic potential flow about complex configurations. A new technique has been used for evaluating the potential values in the field cells intersecting the body surface panels. These potential values then serve as Dirichlet boundary conditions for computing the potentials in the field by a finite volume Successive Line Over Relaxation (SLOR) scheme. In this approach there is no need to evaluate the potentials anywhere in the field by direct application of Green's third identity, thus significantly reducing computer processing time and storage requirement, while improving accuracy of surface pressure prediction and shock capture, as results indicate. The capability of tackling additional complex geometry with ease, the primary advantage of the integral equation approach, is demonstrated by using the same field grid for wing-alone and wing-body combination cases, while maintaining the solution accuracy.

An investigation was carried out to study the parameters affecting single-jet ground-effect hover lift loss and to identify the cause(s) behind the large discrepancies in lift loss between the experiments of Wyatt of RAE Bedford and Corsiglia et alof Nasa Ames. The cause of the discrepancies was traced to a single geometrical parameter: baffle plate edge geometry, which significantly affected the flow separation underneath the plate. In contrast, the out-of-ground lift loss is insensitive to the edge geometry, but can be significantly affected by room size restriction. The investigations have highlighted the importance of accurately representing the edge geometry in ground effect testing of Vstol aircraft, and the importance of the test environment when conducting out-of-ground hover experiments.

This paper describes the development of a simple theory of the longitudinal static stability of the hang-glider. The classical theory, as developed for the conventional aeroplane, is modified to accommodate the particular features of the hang-glider. When the appropriate assumptions are made, the theory provides simple insight into the controls fixed and controls free stability and control characteristics of the hang-glider. The validity of the theoretical models is successfully demonstrated by application to a typical fifth generation hang-glider wing for which good quality aerodynamic data were available.

A simple model is presented for an aerofoil with a recirculating Prandtl-Batchelor region behind a spoiler. Using thin aerofoil theory the model is posed as a pair of coupled nonlinear singular integrodifferential equations for the shape of the separating streamline and the distribution of vorticity along the aerofoil. These equations are solved numerically and results are presented. In particular, some conclusions are drawn regarding the lift on such aerofoils.

An experimental study has been performed manipulating a fully developed turbulent channel flow, by means of blade manipulators known as outer layer devices (Olds). A large amount of investigation has been performed for boundary layer flow, whereas little research is available for internal flow manipulation. The influence on drag reduction for different configurations (single and tandem) and for some geometric parameters (distance from the wall and blade gap), have been analysed. Reynolds number effect has also been investigated. Some of the mechanisms involved in the skin friction reduction process are examined, in terms of time-space integral scales, Reynolds stresses and spectral analysis. Results show better efficiency for tandem configurations. These give high local skin friction reductions, up to 20%, which are strongly dependent on the manipulator distance from the wall, but have very little dependence on the blade gap and Reynolds number. Turbulence analysis displays reduced fluctuations in all three directions — as with space-time integral scales. Evidence of suppression for the large structures is also shown by spectral analysis. From a global balance it has been verified that no net drag reduction is obtained due to the additional drag introduced by the manipulators.