A three year project is proposed to make the advances necessary to allow the exploitation of Computational Fluid Dynamics for the simulation of flight. Flight simulation is based on solving Newton's second law of motion for the aircraft which various forces arising from gravity and aerodynamics, Various simplified models are normally used to represent the aerodynamic forces. The generation of these models can require substantial wind tunnel testing. As an alternative it is possible that computer simulation can be used to generate the necessary data if the simulation itself can be made to execute fast enough. The first part of this proposal is to develop and demonstrate a fast method for data set generation, based on a nonlinear frequency domain method for the Euler equations. A nonlinear frequency domain method will be implemented to allow the rapid generation of datasets for current flight dynamics simulations. Further the CFD simulation will be used to directly provide the aerodynamic forces to Newton's second law, allowing a general treatment of the aerodynamic forces without the simplifications which can be inherent in simpler approaches. The directly coupled simulation is however computationally very expensive and is likely to be necessary only for extreme manoeuvres. These two approaches will be evaluated both for moderate and extreme manoeuvres. A dataset from the MoD will be used for initial validation of the CFD predictions, followed by a generic Hawk trainer model and concluding with the proposed FLAVIIR demonstrator vehicle. Close collaboration with flight dynamics experts at Cranfield will be exploited to ensure that the work is compatible with current flight simulation practice and that maximum immediate exploitation of the results of the project is made. The cost of the project is 197,911.

Radio frequency glow discharges are been used in microelectronic device fabrication, ozone generation and in gas laser excitation. Such discharges operating at atmospheric pressure have been shown to produce jet flows to be used for flow control. Some of recent results obtained from our laboratory clearly confirmed these claims. Surface plasma actuators are simple device with no moving parts or ducting, which have high frequency response and thus have a realistic possibility for aeronautical applications. Already, tests have been conducted for airfoils and turbine blades for possible control of transition, skin-friction drag and flow separation in the last year of so. However, there is still a lack of information on surface plasma physics and associated fluid dynamics to fully utilise the devices for flow control. The production mechanism of wall jets by surface plasma is not well understood, nor is the optimum condition for plasma excitation in flow control. These are precisely the reasons why we propose this research, so that we can advance our understanding on surface plasma for many aeronautical applications, flow separation control in particular.In this investigation we would like to study active control of flow separation during static and dynamics stall. Control of static stall can be investigated by placing surface plasma actuators before the separation point over a circular cylinder with a view to delay flow separation. Here, the time averaged lift and drag forces should indicate the effectiveness of separation control. Control of dynamics stall over a lifting surface can be carried out by reducing the area of separation region or even to recover from separation by using surface plasma actuator. Novelty of this approach is that a real-time detection of flow separation over the body surface is not required, as the vortices are periodically shed from the cylinder surface. Besides, the flow around a circular cylinder is a subject that has been studied by many researchers, therefore there are enough database to help validate our baseline measurements.PIV (Particle Image Velocimetry) system is becoming a common flow measurement technique in fluid dynamic research in recent years, where an entire velocity field in a light-sheet plane can be obtained. With PIV system, small particles in the flow shone by the laser light sheet are photographed in a short interval with a digital camera. The distance and direction of movement of each flow particle gives the velocity vector, thereby globally mapping the velocity field. In our study, flow images will be captured at 1 kHz at a full camera resolution of 1600x1200 pixels for 8 seconds, with 20 mJ of energy being produced by the laser. All of these equipments will be made available from EPSRC Engineering Instrument Loan Pool for this study. The PIV measurements will be complimented by other techniques, such as hot-wire measurements and flow visualisation, which will give confidence in our results, add insight into vortical structures during flow separation and provide better understanding of the mechanisms in which flow separation control with surface plasma can be carried out.

The present proposal is the 3rd (LESUK_3)in a sequence begun in 1995 as part of a focussed initiative by a consortium of UK Universities to compete at world class level in developing and applying Large Eddy Simulation methods to complex engineering problems, with a particular emphasis on aerospace. The purpose of LESUK_3 is to produce accelerated devlopment of the LES technique where convincing demonstrations may be produced so that both academic and industrial CFD communities will recognise the benefits of LES and adopt this for future aerospace applications. The project is divided into work packages which give a balance between (i) addressing fundamental LES algorithm issues, and (ii) demonstrating to industry the progress achieved by applying the developed LES methods to a range of aerospace application challenges such as highly swept wings, noise generation from cavities, airfoils and jets, and vortex breakdown phenomena relevant to gas-turbine combustors.

This project concerns the invention, analysis and implementation of new numerical methods for computationally simulating high frequency wave scattering problems. These problems have diverse applications, for example in modelling radar, sonar, acoustic noise barriers, medical ultrasound, and scattering of radiation by atmospheric particles. Our research is supported by four industrial/research organisations who comprise a steering committee and will provide motivating physical applications for the project.The chief technological difficulty which we face in the project is that of computing accurately wave solutions which are highly oscillatory (i.e. varying very quickly). Standard approximation techniques usually break the domain of the problem up into small ''elements'', and use simple (e.g. polynomial) approximations on each element. Then it is known that about 5-10 elements are required in each wavelength to achieve acceptable accuracy, and so the computational work required grows at least in proportion to the frequency of the wave (and often faster than this). In this sense the methods are termed ''not robust'' as frequency increases.We are going to devise, analyse and implement new robust methods for which the cost to obtain a fixed accuracy is bounded (or at worst grows very slowly) as the frequency increases. The programme involves solving problems not only of approximation of highly oscillatory solutions, but also (and this is often harder) analysing the stability and conditioning (i.e. sensitivity ) of the equations which govern them.The chief device which we will use to achieve our objective is the great body of asymptotic techniques for high frequency wave phenomena, some of which which are well-known in the mathematics and physics communities but which have so far been very little used in numerical computation. Part of our project will involve the derivation of new asymptotic analyses and putting them in a form suitable for use in numerical analysis. Scattering problems will be reformulated in such a way that high frequency parts of the solution are handled explicitly (and thus exactly), leaving only the approximation of low frequency components which can be done with low cost. This approach leads to new, challenging and deep problems in consistency, stability, conditioning and numerical integration which must be solved before the robustness of the methods can be rigorously determined. Some of the problems which we face require applying technology which we know will work because of our earlier studies; others require a significant element of risk and a spirit of adventure.The project will involve four investigators and two PDRAs, one involved primarily in analysis and one primarily in scientific computation. Both will also work on applications of relevance to our collaborators.

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