This paper presents a combined experimental and computational study of annular cavities on a semi-angle cone in a Mach 8·9 flow. A range of cavity length-to-depth ratios has been considered, and a parameter has been determined that distinguishes between ‘weak oscillations’ and ‘strong oscillations’ of the cavity flow. Essentially the work identifies the transition from the case where the flow can be regarded as ‘pure cavity flow’ to that where the flow behaviour is tending towards that of a ‘spiked blunt body’. The CFD simulations also suggest that, for a certain range of cavity scale, the limiting cavity flow state depends upon the flow initialisation process; it may be weak or strongly oscillating.

The paper investigates, by means of a simulation methodology, the flow separating from a 40 degrees backward-swept wing at 9 degrees incidence and Reynolds number of 210,000, based on the wing-root chord length. The Simulation corresponds to LDA, PIV and suction-side-topology measurements for the same geometry, conducted by other investigators specifically to provide validation data. The finest block-structured mesh contains 23·6 million nodes and is organised in 256 blocks to maximise mesh quality and facilitate parallel solution on multi-processor machines. The near-wall layer is resolved, to a thickness of about y+ = 20, by means of parabolised URANS equations that include an algebraic eddy-viscosity model and from which the wall-shear stress is extracted to provide an unsteady boundary condition for the simulation. The numerical solution is in good agreement with the experimental behaviour over the 50-70% inboard portion of the span, but the simulation fails to resolve some complex features close to the wing tip, due to a premature leading-edge vortex breakdown and loss in vortex coherence. The comparisons and their discussion provide useful insight into various physical characteristics of this complex separated wing flow.

The present paper continues the work of Zhu et al. The closed-form expressions for the evaluation of forces on a body in compressible, viscous and rotational flow derived in the previous paper have been extended to different forms. The expressions require only a knowledge of the velocity field (and its derivatives) in a finite and arbitrarily chosen region enclosing the body. The equations are implemented on three-dimensional inviscid flows over wings and wing/body combinations. Further implementation on three-dimensional viscous flows over wings has also been investigated.

The long-term goal is to design and manufacture optimal ‘on-demand’ vortex generators, ‘dimples’ that can produce vortices of prescribed strength and duration for the real-time control of aerodynamic flows that are either undergoing transition or are fully turbulent, attached or separating. Electro-active polymers (EAP) are ideal for a dimple control surface, offering high strain rate, fast response, and high electromechanical efficiency. EAP can also be used as the basis of a resistanc – or capacitance – change pressure sensor, development of which has just begun. In terms of manufacture, inkjet printing of EAP also offers a paradigm shift such that a monolithic control surface is a very real possibility. Important features for integration into a control system are robustness and a predictable, repeatable motion. With these objectives in mind, the suitability of EAP-based actuators is assessed both mechanically and aerodynamically. The ultimate goal is to integrate these devices, along with shear-stress and pressure sensors and distributed control, also under development, into a flexible ‘smart skin’ which could be incorporated into an airframe structure. The response of a laminar boundary layer to forcing is investiagted using mechanical dimples.

A number of experimental studies have shown that postbuckling stiffened composite panels, loaded in uniaxial compression, may undergo secondary instabilities, characterised by an abrupt change in the buckled mode-shape of the skin between the supporting stiffeners. In this study high-speed digital speckle photogrammetry is used to gain further insight into an I-stiffened panel’s response during this transient phase. This energy-dissipating phenomenon will be shown to be able to cause catastrophic structural failure in vulnerable structures. It is therefore imperative that an accurate and reliable methodology is available to predict this phenomenon. The shortcomings of current non-linear implicit solution schemes, found in most commercially-available finite element codes, are discussed. A robust and efficient strategy, which utilises an automated quasi-static/pseudo-transient hybrid scheme, is presented in this paper and validated using a number of experimental tests. This approach is shown to be able to predict mode-jumping with good accuracy.

We use standard tools of the theory of dynamical systems such as phase plots, bifurcation diagrams and basins of attraction to analyse and understand the dynamic behaviour of a typical aerofoil section under dynamic stall conditions. The structural model is linear and the aerodynamic loading is represented by the Leishman-Beddoes semi-empirical dynamic stall model. The loads given by this model are nonlinear and non-smooth, therefore we have integrated the equation of motion using a Runge-Kutta-Fehlberg (RKF45) algorithm equipped with event detection. We perform simulations of the motion for a range of Mach numbers and show that the model is very sensitive to small variations. This is evidenced by the presence in the bifurcation diagram of co-existing attractors or, in other words, by the existence of more than one steady-state motion for a given Mach number. The mechanisms for the appearance and disappearance of the co-existing attractors are elucidated by analysing the evolution of their basins of attraction as the Mach number changes.

Commercially-driven air traffic management (ATM) innovations typically aim to increase air space capacity and/or reduce delays. Here, their potential application for environmental mitigation is discussed. Both carbon dioxide (CO2) and non-CO2 climate impacts are considered, as are noise and air quality issues. We outline the technological, scientific and political barriers to an integrated approach to applying ATM technologies to environmental mitigation. These issues highlight the need to improve comparison and prioritisation of the emissions and effects of aviation.

This paper reports results from numerical computations of low engine order and blade-passing forced response on the rotor of a high pressure turbine due to severe damage to a single nozzle guide vane. The computations are performed using a time-domain, nonlinear viscous compressible flow simulation code. The flow and the levels of forcing for a few selected modes are compared for the undamaged and the damaged configurations. The results show that the response in various modes is affected to a different extent by the damage. The main blade-passing response was found to be largely unaffected, if not marginally reduced. On the other hand, the vibration levels for some modes were seen to be up to eight times higher because of the low-order excitation harmonics created by the damaged passage.