The current understanding of periodic transonic flow is reviewed briefly. The effects of boundary-layer transition, non-adiabatic wall conditions and modifications to the aerofoil surface geometry at the shock interactions on periodic transonic flow are discussed. Through the methods presented, it is proposed that the frequency of periodic motion can be predicted with reasonable accuracy, but there are limitations on the prediction of buffet boundaries associated with periodic transonic flows. Several methods have been proposed by which the periodic motion may be virtually eliminated, most relevantly by altering the position of transition fix, contouring the aerofoils surface or adding a porous surface and a cavity in the region of shock interaction. In addition, it has been shown that heat transfer can have a significant effect on buffet.

This paper presents the application of a relatively new technique of fluidic thrust-vectoring (FTV), named Co-flow, for a small gas-turbines. The performance is obtained via experiment and computational fluid dynamics (CFD). The effects of a few selected parameters including the engine throttle setting, the secondary air mass-flow rate and the secondary slot height upon thrust-vectoring performance are provided. Thrust vectoring performance is characterised by the ability of the system to deflect the engine thrust with respect to the delivered secondary air mass-flow rate. The experimental study was conducted under static conditions in an outdoor environment at Cranfield University workshop that was especially designed for this purpose. As part of this investigation, the system was modelled by CFD techniques, using Pointwise’s Gridgen software and the three-dimensional flow solver, Fluent. Also, Cranfield’s gas-turbine performance code (TurboMatch) was utilised to estimate boundary conditions for the CFD analysis with respect to the integrated nozzle. The presented technique is easy-to-use approach and offers better result for thrust-vectoring problems than previously published works. Experimental results do show the overall viability of the blowing slot mechanism as a means of vectoring the engine thrust, with the current configuration. Computational predictions are shown to be consistent with the experimental observations and make the CFD model a reliable tool for predicting Co-flow fluidic thrust-vectoring performance of similar systems.

In this paper, a new original method based on the least squares method is presented for the conversion of unsteady aerodynamic forces from frequency into Laplace domain, in which the error is written in an analytical form as a function of the Laplace variable, similar to the analytical form of the aerodynamic forces calculated by use of the least squares method. This method is applied on an F/A-18 aircraft (14 symmetric and 14 anti-symmetric modes) for one Mach number and for a set of 14 reduced frequencies. Two different types of results are obtained and analysed: aerodynamic force approximations in the Laplace domain and flutter speeds and frequencies values. For a better comparison of these results, different lag term numbers are used. Results obtained by this new method are better in terms of execution speed and precision than the results obtained by use of the least squares method.

Some in-service deterioration in any mechanical device, such as an aircraft’s gas-turbine engine, is inevitable. However, its extent and rate depend upon the qualities of design and manufacture, as well as on the maintenance/repair practices followed by the users. Deterioration of an engine normally results in the engine seeking a different steady operating-point relative to that for an engine without any deterioration. The variation in engine’s steady operating point leads to changes in the specific fuel consumption (SFC) and/or fuel flow (FF). Any rise in SFC and/or FF and thereby the increased quantity of fuel required is of prime importance in military aviation.

For a military aircraft’s mission-profiles (consisting of several flight-segments), using a bespoke computer simulations, the consequences of low-pressure compressor’s deterioration of an aeroengine upon the weight of the fuel that has to be carried and consumed are predicted. This will help in making wiser management decisions (such as whether to remove an aero-engine from the aircraft for maintenance or to continue using it with some changes in aircraft’s mission profile). Hence improved engine utilization can be achieved, so resulting in lower overall life-cycle costs.

The dynamic inflow model is a powerful tool for predicting the induced velocity distribution over a rotor disc. On account of its closed form and simplicity, the model is especially practical for studying flight mechanics or for designing control systems for helicopters. Scant attention has, however, been paid so far in utilising the dynamic inflow model to analyse an autorotating rotor, which is different from a powered rotor in the geometric relation between the direction of the inflow and the rotor disc. Autorotation is an abnormal condition for helicopters, but for gyroplanes it is the normal mode of operation. Therefore the theoretical discussion on an autorotating rotor is of importance not only to improve the understanding of present gyroplanes, but also in the development of new gyroplanes and to analyse the windmill-brake state of helicopters. Dynamic inflow modelling is reviewed from first principles, and this identifies a modification to the mass flow parameter. A qualitative assessment of this change indicates that it is likely to have a negligible impact on the trim state of rotorcraft in autorotation, but a significant effect on the dynamic inflow modes in certain flight conditions. This is confirmed by numerical simulation, although considerable differences only become apparent for steep descents with low forward speed. It is concluded that while modification of the mass flow parameter is perhaps mathematically accurate, for practical purposes it is required only in a limited area of the flight envelope of autorotating rotorcraft.

This 2007 Lanchester Lecture covered a theoretical result, thought to be new and in print in the Journal of Fluid Mechanics, and some lines of thought on the interpretation of induced drag and recurring paradoxes which interfere with teaching ‘how wings work’. Some of these were presented in the author's 1998 Annual Review. The difficulties are not confined to drag, but also concern lift; they are no less severe in two dimensions than in three. The flow-field in the far wake of an aircraft is examined with the primary purpose of identifying lift and drag in a simple and unified manner, preferably an intuitive one acceptable by novices (and even by those who mind using Bernoulli's equation!).