Computational Fluid Dynamics
Turbulent Flows and Vortical Flows
Environmental Fluid Dynamics
Many processes of practical importance can be viewed and interpreted in terms of their basic fluid mechanics. Research in our traditional areas continues but new directions with new emphases are opening up. Experimental, computational and analytical fluid dynamics are starting to work in partnership bringing their complementary strengths to bear on understanding real problems.
Within the group is located a specialised CFD (Computational Fluid Dynamics) Laboratory. This conducts research into all aspects of the CFD process including three-dimensional computational geometry, geometry parameterisation, and optimisation, mesh generation for arbitrary 3D domains, steady and unsteady Reynolds Averaged Navier Stokes simulations, large Eddy simulations, noise generation, combustion and acoustic-coupled instabilities. Our emphasis is on physical modelling to help solve real industrial problems. The CFD Laboratory has recently formed a Collaboration Partnership with Rolls-Royce to develop the company codes and systems. The group also collaborates strongly with other groups in the department, especially the Energy, Turbomachinery, Structures and Design groups. Unusually for a university these days, the group has excellent, high quality wind tunnel facilities, which are used together with CFD to solve a very wide range of fluid mechanics problems. This combination of computational and experimental resources has put the group in a strong position to interact with the oil and gas as well as the aerospace and power-generation sectors of industry. The Group enjoys good industry EPSRC and EU support. All the group's research emphasises the importance of close coupling between computation and experiment, with all members of the group working together in the same laboratory. Overall our research impinges on many important practical areas: blade cooling and life in gas turbines, fan noise, compressor stall, design optimisation, gas turbine combustion, flow disturbances caused by the wakes of large aircraft, the interaction of boundary layers with shocks on supersonically moving bodies, the noise of turbojets, the design of safer parachute and gliding devices, the erosion of river beds by wave action. Increasingly the protection of our environment provides strong motivation to deploy fluid mechanics in new ways: for example, we have industrially funded projects on the important problem areas of aeroengine noise and the instabilities of low NOx combustions.
Professor W.N. Dawes
Dr R.E. Britter
Dr R.S. Cant
Dr A.M. Savill
The CFD Laboratory is now well established and well-founded. Our strategy is to identify and perform fundamental research to enable a range of very practical problems to be attacked. The CFD activity is positioned to draw together cross-disciplinary modelling, not just in the areas of fluids and combustion modelling (our traditional strengths) but also moving to encompass other important problems in, for example, aeroelasticity of structures and process industry flows.
Our core competence lies in the ability to draw on fundamental modelling using DNS and LES in both combustion and turbulence/transition to improve practical, Reynolds averaged models and then apply this to real problems via state of the art unsteady, solution-adaptive, flow simulation in complex geometries. Funding is robust and from a variety of sources. Strong links have been forged with industry and the CFD lab has been selected to participate with Rolls-Royce and BAe in two Defence Aerospace Research Partnerships one in unsteady flow (PUMA) and one in turbulence/transition modelling (M*).
Dr H. Babinsky
Most research carried out in the high-speed lab is concerned with the understanding and control of shock wave/boundary layer interactions. The recent addition of a two-component LDA system now allows the study of turbulence properties in such interactions. One of the physical effects under investigation is surface roughness and previous research combining a theoretical study based on triple-deck theory and experiments in the high-speed wind tunnels has now been published(B1). More research into fundamental boundary layer physics is currently under way, supported by an EPSRC grant in co-operation with DNS simulations at the University of Southampton.
There are several projects investigating novel mechanisms for shock control on transonic aircraft wings, ranging from passive control(B7), via streamwise slot control to three-dimensional bumps. The recent work on slots and grooves has shown that these devices can reduce wave drag by changing the shock structure while also introducing beneficial streamwise vorticity into the flow, in a manner similar to vortex generators.
Other current research projects include a study of flow through porous surfaces, such as encountered in flow control applications. A new theoretical formulation describing such flows has been developed and published(B9).
A further EPSRC funded project, in conjunction with Professor Dowling (Acoustics) and CFD studies performed by Dr Hynes at the Whittle Lab is investigating unsteady transonic flow over an aerofoil in an oscillating free-stream. The results of this study will be used to formulate new methods of predicting helicopter noise, including oscillating shock noise. The high-speed aero-lab is also involved in the development of a new MEMS based fast response 5-hole flow sensor which is described elsewhere.
Dr T.B. Nickels
Dr W.R. Graham
Turbulent flows occur in many important engineering applications. These flows are extremely complex involving seemingly random and chaotic motions. The physics of these flows is still not fully understood and the structure of turbulent flows is one of the remaining unsolved problems in classical physics.
Turbulent boundary layers are turbulent flows that form close to plates and their behaviour determines the drag on bodies in motion. In an effort to understand turbulent flows new structural models have been developed in collaboration with Professor Ivan Marusic at the University of Minnesota which highlight the differences between turbulent boundary layers and free shear flows such as turbulent jets.
The separation of turbulent boundary layers is an important phenomenon that can radically change the drag on bodies. One particular example is in the stalling of aircraft wings that occurs when the aerofoil is at a large angle to the oncoming flow. This can lead to a dramatic drop in lift and increase in drag.
This behaviour is very difficult to predict due to the fact that the detailed physics of the process is not well understood. Careful experiments concentrating on the structure and topology of separating flows should lead to improved physical models and predictions. To this end a new boundary layer water-tunnel is being constructed and new experimental techniques are being developed.
This work is part of a more general study of the response of turbulent boundary layers to changes in external conditions(B12).
A collaborative project with Dr W Graham on merging of aircraft trailing vortices has also been initiated that involves experiments and numerical simulations.
Work on the hazard posed by trailing vortices behind aircraft has continued with studies of the process of transition from the complex near-field wake to the classical far-field counter-rotating vortex pair. Extensive experimental efforts have yielded a much more detailed characterisation than was previously available, furthering understanding of this complicated phenomenon.
Dr R.E. Britter
A major field campaign in the City of Birmingham on urban air quality was completed. This was in conjunction with the Department of Chemistry, University of Bristol. Tracer pollutants were tracked within the urban canopy through the centre of Birmingham(B3,B4,B5). This novel field experiment is only the second of its type to ever be undertaken.
A close collaboration with the Department of Architecture, University of Cambridge has addressed the problem of the morphology of the urban surface and how best to describe the flow and pollutant dispersion through cities. The use of Digital Elevation Models has been very successful(B13,B14).
These and other studies have led to a review of the general field of the effects of urban and industrial roughness on flow and dispersion(B8). A book on the topic commissioned by the American Institute of Chemical Engineering is to be published in 2001.
Dr J.F.A. Sleath
Work on Coastal Engineering, particularly the way in which sand is moved around by the sea, continues. During the year papers have been published on the novel mechanism for sediment transport under severe wave conditions (plug flow) identified in previous studies, the steady drifts induced by waves over rough beds, and the mechanisms of ripple formation and extinction at high sediment transport rates(B15,B19). The study of sediment entrainment from rippled beds continues.
B1. Babinsky, H., Inger, G.R. The effect of surface roughness on shock wave/turbulent boundary layer interactions. 18th AIAA Applied Aerodynamics Conference, Denver, CO, USA, AIAA paper 2000-3918 (August 2000).
B2. Bertenyi, T., Graham, W.R. An experimental study of the merging of aircraft wake vortices. 18th AIAA Applied Aerodynamics Conference, Denver, CO, USA, AIAA paper 2000-4129 (August 2000).
B3. Britter, R.E., Caton, F., Di Sabatino, S., Cooke, K., Simmonds, P., Nickless, G. Dispersion of a passive tracer within and above an urban canopy: Birmingham, UK, experiment. American Meteorological Society, 3rd Symposium on Urban Environment, Davis, CA, USA (August 2000).
B4. Cooke, K.M., Caton, F., Di Sabatino, S., Britter, R., Simmonds, P.G., Nickless, G. Tracers and dispersion of gaseous pollutants in the urban canopy. 6th EUROTRAC Symposium, EUROTRAC - 2 Symposium 2000, Transport and Transformation of Pollutants in the Troposphere, Garmisch-Partenkirchen, Germany (March 2000).
B5. Cooke, K.M., Simmonds, P.G., Nickless, G., Caton, F., Di Sabatino, S., Britter, R.E. Tracers and dispersion of gaseous pollutants. Proceedings, URGENT (Urban Regeneration and the Environment) Annual Meeting, Cardiff (April 2000).
B6. Dawes, W.N., Dhanasekaran, P.C., Demargne, A.A.J., Kellar, W.P., Savill, A.M. Reducing bottlenecks in the CAD-to-mesh-to-solution cycle time to allow CFD to participate in design. ASME Turbo Expo 2000, 45th ASME International Gas Turbine and Aeroengine Technical Congress, Exposition and Users Symposium, Munich, Germany, ASME paper 2000-GT-0517 (May 2000).
B7. Gibson, T.M., Babinsky, H., Squire, L.C. Passive control of shock wave-boundary-layer interactions. Aeronautical Journal, 104, (1033), 129-140 (March 2000).
B8. Hanna, S., Britter, R.E. Effects of urban and industrial roughness obstacles on maximum pollutant concentrations. Proceedings, NATO CCMS International Technical Meeting on Air Pollution Modelling and its Application, Boulder, CO, USA (May 2000). Published in: Air Pollution Modelling and Its Application XIV; Edited by S.E. Gryning, F.A. Schiermeier, 551-559 (Kluwer Academic, 2001). ISBN 0306465345.
B9. Inger, G.R., Babinsky., H. Viscous compressible flow across a hole in a plate. Journal of Aircraft (AIAA), 37, (6), 1028-1032 (December 2000).
B10. Kellar, W.P., Pearse, S., Savill, A.M. Formula 1 car wheel aerodynamics. Sports Engineering Journal, 2, (4), 203-212 (1999).
B11. Kellar, W.P., Targett, G.J., Savill, A.M., Dawes, W.N. An investigation of flowfield influences around the front wheel of a formula 1 car. Engineering of Sport: Research, Development and Innovation: Proceedings, 3rd International Conference on the Engineering of Sport, Sydney, Australia (June 2000); Edited by A.J. Subic, S.J. Haake, 353-360 (Blackwell Science, 2000). ISBN 0632055634.
B12. Nickels, T.B., Joubert, P.N. The mean velocity profile of turbulent boundary layers with system rotation. Journal of Fluid Mechanics, 408, 323-345 (April 2000).
B13. Ratti, C., Caton, F., Di Sabatino, S., Britter, R.E. Morphylogical parameters for urban pollution models. Proceedings, PLEA (Passive and Low Energy Architecture) Conference, Cambridge, UK, 775-776 (July 2000).
B14. Ratti, C.F., Di Sabatino, S., Caton, F., Britter, R.E. An application of digital elevation model data to urban dispersion modelling. American Meteorological Society, 3rd Symposium on Urban Environment, Davis, CA, USA (August 2000).
B15. Ridler, E.L., Sleath, J.F.A. Effect of bed roughness on time-mean drift induced by waves. Journal of Waterway, Port, Coastal, and Ocean Engineering (ASCE), 126, (1), 23-29 (January/February 2000).
B16. Rycroft, N.C., Savill, A.M., Dawes, W.N. Reynolds-averaged and large-eddy simulations of flow through a tube bundle. Proceedings, 3rd International Symposium on Turbulence, Heat and Mass Transfer, Nagoya, Japan (April 2000).
B17. Savill, A.M., Pittaluga, F. Meeting report: ERCOFTAC Transition Modelling SIG10 Annual Workshop 1999 (1st Workshop of the TRANSPRETURB Thematic Network): Implementation and further application of refined transition prediction methods for turbomachinery and other aerodynamic flows, Cambridge, March 1999. ERCOFTAC Bulletin, 44, 78-79 (March 2000).
B18. Savill, A.M., Pittaluga, F. Meeting report: ERCOFTAC Transition Modelling SIG10 Annual Workshop 2000 (2nd Workshop of the TRANSPRETURB Thematic Network): Implementation and further application of refined transition prediction methods for turbomachinery and other aerodynamic flows, Genoa, Italy, March 2000. ERCOFTAC Bulletin, 45, 7-10 (June 2000).
B19. Sleath, J.F.A. Ripple geometry under severe wave conditions. Proceedings, 27th Conference on Coastal Engineering, Sydney, Australia (July 2000).
B20. Vicedo, J., Vilmin, S., Dawes, W.N., Hodson, H.P., Savill, A.M. The extension of CFD-friendly turbulence modelling to include transition. 8th European Turbulence Conference (ETC8), Barcelona, Spain (June 2000).
B21. Vicedo, J., Vilmin, S., Dawes, W.N., Savill, A.M. Extension of intermittency transport modelling to natural transition in external aerodynamic applications. Proceedings, Royal Aeronautical Society Aerodynamics Research Conference, London (April 2000).
B22. Watterson, J.K., Dawes, W.N., Savill, A.M., White, A.J. Predicting turbulent flow in a staggered tube bundle. International Journal of Heat and Fluid Flow, 20, (6), 581-591 (December 1999).
B23. Yao, Y.F., Savill, A.M., Sandham, N.D., Dawes, W.N. Simulation of turbulent trailing-edge flow using RANS & DNS. Proceedings, 3rd International Symposium on Turbulence, Heat and Mass Transfer, Nagoya, Japan (April 2000).
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Last modified: September 2001