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The purpose of this study is to compare two unsteady actuators: an oscillator and a sweeping jet. Both actuators can produce an oscillating jet of different amplitudes and frequencies without any moving parts, making them an attractive actuator concept. The Coanda effect phenomenon can explain the operating principles of these two unsteady actuators.

A numerical study was conducted to compare the amplitudes and frequencies of fluidic and sweeping jet (SJ) oscillators to obtain an efficient actuator to control separated flows at high Reynolds numbers. For this goal, two-dimensional unsteady Reynolds-averaged Navier-Stokes simulations were carried out using computational fluid dynamics (CFD) fluent code to evaluate the actuator performances. The discrete fast Fourier transform method determined the oscillation frequencies.

The oscillation frequencies gradually increase as the inlet pressure increases. The characteristics and dimensions of the vortices produced in the mixing chamber and feedback loops vary overtime when the injected fluid is swept sideways. The frequencies supplied by the SJ are stronger than those obtained by the fluidic oscillator, which may contribute to improving the aerodynamic performance at a lower power supply cost.

The existence of the splitter in the fluidic oscillator led to the production of separate pulses, which would be useful in various industrial applications, including active control of combustion and mixing processes while other applications such as flow separation control require SJs. With the latter actuator higher and interesting frequencies can be obtained, leading to efficient flow control.

The development of variable geometry in general is traced as applied to aircraft wings with particular emphasis on variable sweepback, including discussion of some experimental aircraft. The characteristics of swept wings illustrate the reason for variable sweep in some advanced aircraft and a comparison made with jet lift. Some of the implications and problems involved in variable sweep design are discussed in detail and some observations made on the weight aspect. To illustrate the discussion, three sketch designs of aircraft with variable sweep are presented.

This paper aims to address shortcomings of current tiltrotor designs, such as the small aspect ratio of the wings, large download and the close proximity of the rotor tips. It also aims to avoid the complex transition of tiltrotors to normal airplane mode.

This design combines tiltrotor and tiltwing aircraft designs into a hybrid that is augmented by active flow control, using a gimbaled channel wing for attitude control in hover.

The proposed hybrid design is based on experimental results of components that were tested individually for potential use in hover and steep ascend from a stationary position.

This research was inspired by the extremely short take-off of the V-22, when its rotors were tilted forward. It combines several design approaches in a unique way to achieve extremely short take-off capabilities combined with high-speed and reduced maintenance costs.

THE purpose of this article is to indicate the developments in aircraft that have appeared since the first post‐war S.B.A.C. Display of 1946. Now is perhaps the time to pause and consider progress in British aviation, particularly as the first turbo‐jet air liner, the Comet, has entered service, the first turbo‐propeller aircraft, the Viscount 700, is being manufactured in quantity, and production orders have been placed for the Hawker Hunter swept‐wing fighter and the Gloster G.A.5 Delta. These aircraft represent a few of the British types evolved in the post‐war period and demonstrate aeronautical advancement.

This paper discusses a large range of layouts that have been studied in relation to both strike and transport V/S.T.O.L. requirements. The performance of aircraft with different powerplant arrangements is considered, with the effects on structure and aerodynamics being based on extensive detail design work.

GIVEN by Dr John Fozard of British Aerospace, who was Chief Designer, Harrier, 1963–78, this paper formed part of the presentation on shipborne V/STOL aircraft held recently at the Royal Aeronautical Society. Dr Fozard reviewed the effects of Harrier jet V/STOL on an evolving world defence scene in the past 20 years. In naval aviation, the advent of the jet aircraft and swept wings forced other developments such as the angled deck and the mirror sight. Large carriers were essential with costs also very high. On the other ‘side of the fence’, jet V/STOL was just beginning with the first P 1127 making its first cautious hovers in 1960. It was developed in the next few years and made the first flight from a carrier of this kind of aircraft. Changing naval fortunes made it policy at one time that tactical air power at sea would be provided by land based aircraft. Later, this began to be overturned and studies were made of smaller carriers, thought they were called ‘through deck cruisers’ or some similar name, for a variety of reasons.

WHEN a high‐speed jet aircraft is flying at transonic speeds — near or just above the speed of sound — a large proportion of the total drag of the aircraft will come from the afterbody of the fuselage. This may be as much as 30–40%, which is a very significant amount to the aircraft designer. The flow over the afterbody is also important because it affects the behaviour of the fin, and because if the flow is oscillatory, this can have adverse consequences on the airccraft. The necessity of maximising knowledge of the after‐body flow while minimising the cost of wind‐tunnel and in‐flight testing is bringing computational fluid dynamics (CFD) into prominence. British Aerospace has recently commissioned a study by CHAM (Concentration Heat and Momentum Ltd) in the application of the extremely sophisticated CFD code PHOENICS to the problem. The study has concentrated upon predicting the effect of jet entrainment on the surface pressure distribution around the afterbody, an area which has previously been difficult to model computationally. A large amount of experimental work has already been carried out using wind‐tunnel measurements, and the study sought first to validate the program by reference to experimental data.

Under this heading are published regularly abstracts of all Reports and Memoranda of the Aeronautical Research Council, Reports and Technical Memoranda of the United States National Advisory Committee for Aeronautics and publications of other similar Research Bodies as issued.

AIRCRAFT ENGINEERING was born in March 1929 of the belief that the emerging technology from which it took its title would become a fundamental element of engineering progress. The keystone of its policy was that it would attempt to meet the needs of engineers and students working in this field and that its contents should be ‘written by engineers — for engineers’. That this venture was fully justified has been amply vindicated by the achievements of the industry during the ensuing 41 years — as recorded in the first 500 issues of this Journal, the major milestone celebrated this month. This is a propitious occasion on which to review the record to date because, although aviation has always been about looking forward, history is instructive and it is the impressive performance of the aerospace industry to date that inspires and motivates confidence in its future.

THE possibility of adopting the compression ignition engine for use in aircraft is one which has been exciting great interest ever since the War. The advantages claimed for such an engine for any type of aircraft are:—