Thirty-eight data sets from static tests of various 65° delta wings in many water and wind tunnels are compared with four empirical vortex breakdown location prediction methods and the results of two Navier-Stokes computations to assess their range of validity in pitch. Vortex breakdown is the sudden expansion and subsequent chaotic evolution of the otherwise orderly, spiraling, leading-edge vortex flow over the upper surface. Large fluctuations occur in vortex breakdown location at static test conditions making accurate experimental determination difficult.

The prediction methods do not account for the seemingly minor geometric details that vary between the models such as thickness, leading-edge bevel angle and radius, trailing-edge bevel angle, sting mounting, instrument housings, etc. These geometric variations significantly affect the position of vortex breakdown and degrade the accuracy of the predictions. The large changes in the flow produced by small geometric changes indicate that an efficient flow control strategy may be possible. Many of the data sets are not corrected for tunnel wall effects, which may account for some of the differences. Data presented herein are as published by the original authors, without additional corrections.

The European Supersonic Commercial Transport’s control surface configuration is based largely on Concorde’s and has been scaled to provide comparable un-augmented stability and manoeuvre performance. Hence, optimising the surface size could provide significant performance benefits in terms of reduced drag, noise, structural and actuator power requirements. Adequate control power will be required to meet current civil aviation regulations whose primary aim is to ensure the aircraft can be flown safely during both normal and emergency operation. Additional design criteria, combined with the optimum longitudinal control laws, are required to ensure desirable handling qualities with minimum pilot workload. Two critical low-speed flight conditions, normal and emergency, together with associated aircraft configurations for control surface sizing have been identified. The rudder must provide sufficient control power to achieve positive heading changes subsequent to a double asymmetric engine failure during normal operation. The fin should be sized to satisfy Dutch roll stability criteria with the un-augmented aircraft in its emergency configuration. The dual functionality of the elevons require that they are sized using both pitch and roll performance and handling quality criteria. The bank angle capture requirement provides the most critical elevon design case, the satisfaction of which also ensures adequate pitch control power. Validation using ‘pilot-in-the-loop’ simulation will be required whilst more explicit control surface size optimisation would require the definition of limiting airspeeds and operating conditions applicable to the European Supersonic Commercial Transport. Additional studies of control power requirements during transonic and supersonic cruise may also be required.

Experiments have been performed investigating the effectiveness of steady tangential blowing, with the blowing slot located downstream of separation (but inside the separation bubble) to control a trailing-edge separated flow at low speeds. Trailing-edge separation was induced on a two-dimensional aerofoil-like body and the shear layer closure occurred in the near-wake. Measurements made consisted of model surface pressures and mean velocity, turbulent shear stress and kinetic energy profiles in the separated zone using a two-component LDV system. It is explicitly demonstrated that the novel concept of tangential blowing inside the bubble can be an effective means of control for trailing-edge separated flows as well. Blowing mass and momentum requirements for the suppression of wall and wake flow reversals have been estimated.

Robotic in-orbit servicing has yet to be realised due to a number of technical difficulties. One such difficulty is analysed here. The requirement for force control in robotic manipulation imposes significant design requirements on space robots by virtue of the lack of a mounting platform to react against external forces and torques. The spacecraft attitude control system must effectively serve the same role as the ground in terrestrial manipulators. The reaction torques imposed on the spacecraft due to the manipulators is high when force control is used in grappling targets in space, limiting the choice of attititude actuator to control moment gyroscopes.

Most Individual Blade Control (IBC) approaches have attempted to suppress the rotor vibration by actively altering the varying aerodynamic loads on the blade using techniques such as trailing-edge servoflaps or imbedded piezoelectric fibres to twist the blade. Unfortunately, successful implementation of these approaches has been hindered by electromechanical limitations of piezoelectric actuators. The Smart Spring is an unique approach that is designed to suppress the rotor vibration by actively altering the structural stiffness of the blade out of phase with the time varying aerodynamic forces. The Smart Spring system is able to adaptively alter the stiffness properties of the blade while requiring only small deformations of the actuator, which overcomes the major problems inherent in the former approaches. The theoretical characterisation of the Smart Spring system as a class of active Tunable Vibration Absorbers (TVA) is presented in the paper. A real-time adaptive control system was developed for a Smart Spring to suppress vibration. Initial aerodynamic wind tunnel test results using the proof-of-concept model of the device in a fixed blade indicate that the Smart Spring can evolve into a powerful approach for IBC.

The Department of Mechanical Engineering at the University of Strathclyde has developed a novel flight experience/test course for undergraduate Aeronautical Engineers. In common with similar courses at undergraduate level the course contains practical instruction in how an aircraft is flown, an analysis of its stall characteristics and an assessment of an aircraft’s performance and stability. However, uniquely, the Strathclyde course consists of dual instructional flights in two seat gliders. This paper contains a detailed description of the flight experience/test course developed at Strathclyde and its incorporation into the undergraduate curriculum. A critical analysis of its delivery is also presented.

The work described here concentrates on under-expanded, axisym-metric turbulent jets issuing into quiescent conditions. Under-expanded turbulent jets are applicable to most aircraft propulsion applications that use convergent nozzles. Experimental studies used laser doppler velocimetry (LDV) and pitot probe measurements along the jet centreline. These measurements were made for two nozzle pressure ratios (2·5 and 4·0) and at various streamwise positions up to 10 nozzle diameters downstream of the nozzle exit plane. A computational fluid dynamics (CFD) model was developed using the Fluent code and utilised the RNG K-ε two-equation turbulence model. A mesh resolution of approximately one hundredth of nozzle exit diameter was found to be sufficient to establish a mesh independent solution.

Comparison of the jet centreline axial velocity (LDV data) and pressure ratio (pitot probe data) showed good agreement with the CFD model. The correct number of shock cells had been predicted and the shock strength agreed well between the experiments and numerical model. The CFD model was, however, found to over-predict the shock cell length resulting in a longer supersonic core. There was some evidence, based on analysis of the LDV measurements that indicates the presence of swirl and jet unsteadiness, which could contribute to a shortening of the shock cell length. These effects were not modelled in the CFD. Correlation between the LDV and pitot probe measurements was generally good, however, there was some evidence that probe interference may have caused the premature decay of the jet. Overall, this work has indicated the good agreement between a CFD simulation using the RNG k-ε turbulence model and experimental data when applied to the prediction of the flowfield generated by under-expanded turbulent jets. The suitability of the LDV technique to jet flows with velocities up to 500ms-1 has also been demonstrated.

The problem of induced drag reduction during formation flight is revisited by means of a simple aerodynamic model based on lifting line theory. The optimum configuration for minimum induced drag is analysed both in and out of the ground effect and the influence of the main geometrical and aerodynamic parameters is considered. The results are discussed and compared with existing numerical and experimental data.

An analysis is presented both of flight test and simulation data obtained from a gyroplane aircraft. This class of rotary-wing vehicle has found limited application in areas other than recreational flying, however the accident rate has been such that it has prompted the study of the configuration’s stability and control characteristics. It is concluded that the flight dynamic response of the gyroplane examined is dominated by a fast, non-stable mode, affecting all states and thus increasing pilot workload. Simulation results indicate that the position of the centre of gravity significantly influences the stability of this mode.

A new similarity parameter has been used for analyzing the unsteady aerodynamic behaviour of vehicles undergoing sinusoidal pitching motion. If this parameter is identical for two unsteady manoeuvres with different reduced frequencies and oscillation amplitudes, the corresponding hysteresis loops of the force and moment collapse on each other. To support and verify this, extensive unsteady wind tunnel tests have been conducted on a standard model, which is a well known fighter type configuration. The acquired data were used to train a certain type of neural network, called the Generalised Regression Neural Network (GRNN), to reduce the number of wind tunnel runs. The scheme, once proved to give the correct results for various conditions, was applied to extend the experimental data to other conditions that have not been tested in the tunnel. Both the predicted and acquired tunnel data were used to show the performance of the similarity parameter.

Active drag reduction systems, such as hybrid laminar flow control (HLFC), have the potential for significant fuel savings; however, this is at the expense of an increase in aircraft weight and engine power off-take. A computer program – capable of accurately determining the trip fuel for a given mission profile – has been developed. The program was validated against manufacturer’s payload-range data, and then modified to emulate the installation of an active drag reduction system, by incorporating changes to the drag polars, specific fuel consumption (SFC) data and operating empty weight (OEW). Results of sensitivity studies are presented that enable the reduction in trip fuel to be determined for given changes in CD, SFC and OEW. The underlying assumption of linear independence of the three parameters is explored. The linearised method was observed to underestimate the fuel savings of the HLFC aircraft by approximately 0·6% compared to an analysis which took into account the coupling between the parameters. A mathematical relationship has been established to estimate the impact on cruise fuel burn arising from relative changes to the aircraft’s mass, lift-to-drag ratio and SFC.

Modern civil transport aircraft utilise increasingly complex command and stability augmentation systems to restore stability, optimise aerodynamic performance and provide the pilot with the optimum handling qualities. Provided it has sufficient control power a second generation fly-by-wire supersonic transport aircraft should be capable of exhibiting similarly desirable low-speed handling qualities. However, successful flight control law design requires identification of the ideal command response type for a particular phase of flight, a set of valid handling quality design criteria and piloted simulation evaluation tasks and metrics. A non-linear mathematical model of the European supersonic transport aircraft has been synthesized on the final approach to land. Specific handling quality design criteria have been proposed to enable the non-linear dynamic inversion flight control laws to be designed, with piloted simulation used for validation. A pitch rate command system, with dynamics matched to the aircraft’s flight path response, will consistently provide Level 1 handling qualities. Nevertheless, pre-filtering the pilot’s input to provide a second order pitch rate response, using the author’s suggested revised constraints on the control anticipation parameter will generate the best handling qualities during the terminal phase of flight. The resulting pre-filter can be easily applied to non-linear dynamic inversion inner loop controllers and has simple and flight proven sensor requirements.

Experiments were carried out on jets issuing from circular nozzles with grooved exits and the results compared with those of the plain nozzle. The plain nozzle had an exit diameter of 10mm. Because of the introduction of semi-circular grooves at the exit, the effective or equivalent diameter of the grooved nozzles was 10·44mm. The groove lengths were varied as 3, 5 and 8mm. The nozzles were operated at fully expanded sonic and underexpanded exit conditions. The corresponding fully expanded Mach numbers were 1·0 and 1·41. The shock cell structure of the underexpanded jets from grooved nozzles appeared to be weaker than that of the plain nozzle, as indicated by lesser amplitudes of the cyclic variation of the Pitot pressure. The iso-Mach contours indicate that the jet spread along the grooved plane is significantly higher than that along the ungrooved plane. Off-centre peaks were observed in the mean pressure profile of underexpanded jets from grooved nozzles. They were probably due to the streamwise vortices shed from the grooves.

The effects on the wall pressure of the plate caused by the introduction of a gap near the ground and the flaps were investigated experimentally. The mean pressure on the plate surface was found to decrease with the size changing of the gap near the ground when the gap size (g) is larger than the flap height (h), but the one in the recirculation region increase with the size of the gap when the gap size is about 0 ≤ g ≤ 2h. Three kinds of flow structure appear with increasing the gap sizes, and the transit point is at g/h = 0·2, 0·8 respectively. For the zigzag flap (d/h = 0·19, d is the height of the zigzag), the variation of wall pressure with g/h is similar to the flat flap in general. The zigzag affects the mean wall pressure in the region of 0 ≤ x/h ≤ 20 (the recirculation zone) and can decrease the fluctuating pressure in the region of x/h > 20 downstream.

A statistical approach is followed for prediction of tolerences of notched strength of composite laminates using the recently proposed improved inherent flaw model (IFM). In order to examine the validity of this approach, the existing fracture data on graphite/epoxy composite laminates containing central holes and cracks were used. The notched strength estimations are found to be within the range of tested values.

An investigation of active control of the swept shock wave/boundary-layer interaction using ‘smart’ flap actuators is presented. The actuators are manufactured by bonding piezoelectric material to an inert substrate to control the bLeed/suction rate through a plenum chamber. The cavity provides communication of signals across the shock, allowing rapid thickening of the boundary layer approaching the shock. This splits the shock foot into a series of weaker shocks forming a lambda structure, thus reducing wave drag. Active control allows optimisation of the unimorph deflection, hence rate of mass transfer.

In this paper, results of the interaction using pressure sensitive paint (PSP) are emphasised. It is shown that the use of PSP, in conjunction with discrete pressure data, enables the main features of the interaction to be observed when the actuators are subject to different deflections.

Laminar separation bubbles formed on NACA 0012 aerofoil near the onset of a stall were investigated to clarify the behaviour of the laminar separation bubble. Measurements were done at a chord Reynolds number of 1·3 × 105. Mean velocity measurements indicate that the long bubble of about 35% chord length is formed at α = 11·5° after the short bubble burst occurred. However, the instantaneous flow visualisation picture indicates that the flow is strongly oscillating at this angle of attack. The phase averaging technique has been applied to analyse this oscillating behaviour. The results indicate that the flow is oscillating between a small separation-reattachment bubble formed near the leading-edge at about a 10% chord length and a large separated region extending over the aerofoil surface. It is suggested that this small separation-reattachment bubble has a similar flow structure to that of the short bubble formed at a lower angle of attack.

Results of numerical simulation of inviscid compressible flow around a generic satellite launch vehicle (SLV) with strap-on boosters using a commercial computational fluid dynamics (CFD) code named Star-CD are experimentally evaluated. Governing equations of flow around the SLV with two and two strap-on boosters were solved in three dimensions using the SIMPLE algorithm in an unstructured tetrahedral mesh, to determine longitudinal aerodynamic coefficients and surface pressure distribution at Mach numbers from 0·6 to 2·0, and angles-of-attack from 0° to 16°. To evaluate the numerical results, 1:100th scale models of the SLV were tested in a trisonic wind tunnel in the same configurations and flow conditions as those analysed numerically. Comparison of results shows reasonable agreement between numerical and experimental values, however, drag coefficients had to be corrected to compensate the effects of base flow and the struts connecting the boosters to the core rocket. This evaluation shows that a relatively simple simulation of flow using a commercial CFD code can be considered an efficient tool for prediction of aerodynamic characteristics of a multi body satellite launch vehicle with a level of accuracy acceptable in the process of preliminary aerodynamic design.

As one aspect of a balance research and development programme, engineers at the Aircraft Research Association (ARA) have addressed the unique problems associated with the design of an internal single piece balance suitable for small military type aircraft models that experience very high loads during a wind tunnel test. The paper details the nature of the problems and the stages undertaken in the design, manufacture and commissioning of an initial prototype balance followed by a re-designed version to meet the stringent requirements. Data from recent tests indicate the quality of the measurements and the suitability of the balance for the testing of fighter type aircraft.