Computational Fluid Dynamics
Flow Instability and Control
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.
Fundamental studies of shock-boundary layer interactions in our blow-down supersonic tunnels, part funded under EUROSHOCK, continued and have now linked up with CFD activity in this area via a large EPSRC grant awarded under the auspices of our Defence Aerospace Research Partnership in Turbulence & Transition Modelling. Work on aircraft vortical wake flows, part funded by EUROWAKE and the CAA, in our large low speed tunnel is contributing to aircraft safety issues. Flow instability(B19,B20,B21) and control continues to be a strong topic, both from the points of view of whole aircraft analysis and also building low order models to participate in control algorithms.
Big contributions are being made, via the European Commission, to debates on environmental concerns. Modelling of hazardous gas release and its interaction
with atmospheric turbulence continues as a speciality. Sediment transport in coastal engineering continues to be studied in our range of flumes, funded in part by EPSRC.
The CFD laboratory is now recognized as a centre of excellence by both aerospace and the oil and gas industry. Collaboration with other groups in the Department is now growing rapidly as the emphasis in real engineering shifts ever more towards multi-disciplinary team work.
Professor W.N. Dawes
Professor A.P. Dowling
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, design optimisation, the behaviour of MEM's etc (even the flow of electrical signals through heart tissue!).
Our core competence lies in the ability to draw on fundamental modelling including 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. This fundamental research in advanced numerics and modelling is currently supporting via about 20 research contracts, six main application areas:
- Aircraft Aerodynamics - multi-element high lift wings; drag reduction via riblets; shock boundary layer interaction control
- Aeroengines and Industrial Gas Turbines - fan noise; stall and instability; turbine aerodynamics and film cooling; combustion noise and instabilities
- Oil and Gas Industry safety Case Analysis - dispersion; deflagration and detonation; blast response and mitigation
- Racing Car Aerodynamics - front wing/end plate/ wheel interaction; cooling intake flows; rear wings
- CAD-to-mesh-to-CFD - a crucial enabling technology underpinning all our activity
- Design Optimisation - including studying para-meterisation itself as well as optimisation strategies.
We have a very advanced range of computing power available, including several multi-processor work stations and a "Boeuwolf" PC cluster together with substantial access to the University's Hitachi Massively Parallel Supercomputer. The combined impact of this is to give us more per capita computer power than any other group in the country!
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*).
A number of publications are now starting to appear from work performed within the framework of the CFD lab(A1,A6,A9,A13,A32,A33,A61,B9,B10,B18,B23,B24,B25,B27,B28) .
Dr H. Babinsky
Dr T.B. Nickels
The aerodynamics of paragliders has been studied for some time in the Department. In particular, several causes for their relatively poor performance have been identified(B3) and various mechanisms for their improvement have been suggested(B2).
Research into the separation of turbulent boundary layers has been initiated. The separation of turbulent
boundary layers is an important phenomenon that occurs in a number of industrially important flow.
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.
This work is part of a more general study of the response of turbulent boundary layers to changes in external conditions(B22).
A collaborative project with Dr W R Graham on merging of aircraft trailing vortices has also been initiated.
Dr H. Babinsky
Research in compressible aerodynamics has focused on the area of shock wave boundary layer interactions, with particular emphasis on civil transport applications. There are also a number of studies investigating fundamental physical mechanisms of such interactions.
Research into the active and passive control of transonic shock wave boundary layer interactions as part of the EUROSHOCK II programme has been concluded. In this research, a swept shock wave interacted with a turbulent boundary layer and various control systems including porous surfaces with and without suction as well as discrete suction were studied experimentally and numerically. The results demonstrated that suction can be used to modify shock strength and boundary layer growth throughout the interaction and is therefore capable of influencing viscous and wave drag on transonic aircraft. The results of this programme are due to be published in the Euroshock final report; some aspects have also been reported(B4). A similar control device for transonic wings, streamwise slots, is currently under investigation in conjunction with DERA Bedford.
Aerodynamic controls often incorporate some form of suction through porous surfaces. A new theoretical law for such flows is currently under development and first results are promising(B17).
The effect of surface roughness on supersonic shock/boundary layer interactions has been studied in conjunction with a theoretical approach using triple deck theory. This programme is still ongoing and some early results are presented(B5). Some earlier work in the field of shock wave dynamics has also been published(B1).
Future EPSRC funded research programmes include a fundamental study of turbulence effects in shock/boundary layer interactions and an investigation into shock oscillations on helicopter blades.
Dr W.R. Graham
Optimal control ideas have been applied to low-order models derived from numerical simulations of the flow past a cylinder(B12,B13). The work has called into question the commonly-held view that low-order models which give accurate representations of uncontrolled unsteady flows can be used as a basis for control of the unsteadiness. Instead, the low-order model must be extended so that it includes a description of the effects of control action. Simulations of an optimal control strategy based on such a model have shown promise in reducing the level of unsteadiness in the cylinder wake.
Work has also been carried out on the fundamental theory of aircraft stability(B11). A new, asymptotic, approach has been developed, allowing analytical approximations to the classical aircraft modes of motion to be obtained without recourse to the a priori assumptions used in the past. The theory has been introduced into the Department of Engineering's Part IIB course on Aircraft Stability and Control.
Dr J.F.A. Sleath
Investigation of the way in which sand is entrained from rippled beds in oscillatory flow continues. Now experimental equipment has been developed and tested and a start has been made on the numerical modelling of these flows.
Earlier work, which showed the existence of a plug flow mechanism at flow reversal, has been extended(B29,B30) and wave tank measurements of the way in which the drift current generated by waves is affected by bottom roughness have been accepted for publication.
Dr R.E. Britter
The development of an operational shallow model for releases of hazardous materials within sites having complex topography has been completed and the extensive validation undertaken(B14,B15,B16).
Work was completed on scientific model evaluation(B8) and on the behaviour of high pressure gas releases in naturally ventilated offshore modules in the petroleum industry(B7,B26). The latter papers are currently being developed into an operational Workbook for the industry. A broad review of recent research on the dispersion of hazardous materials was presented to the A.I.Ch.E.(B6).
B1. Abe, A., Ojima, H., Ogawa, T., Babinsky, H., Takayama, K. Animated display of sequential holographic interferograms of shock wave/vortex propagation. Proceedings, 22nd International Symposium on Shock Waves, London, Paper 4850 (July 1999).
B2. Babinsky, H. Aerodynamic improvements of paraglider performance. Proceedings, 17th AIAA Applied Aerodynamics Conference, Norfolk, VA, USA, AIAA Paper 99-3148, 362-367 (June/July 1999).
B3. Babinsky, H. The aerodynamic performance of paragliders. Aeronautical Journal, 103, (1027), 421-428
B4. Babinsky, H. Control of swept shock wave/turbulent boundary-layer interactions. Proceedings, 22nd International Symposium on Shock Waves, London, Paper 0051 (July 1999).
B5. Babinsky, H., Inger, G.R., McConnell, A.D. A basic experimental/theoretical study of rough wall turbulent shock/boundary layer interaction. Proceedings, 22nd International Symposium on Shock Waves, London,
Paper 0050 (July 1999).
B6. Britter, R.E. Recent research on the dispersion of hazardous materials. Proceedings, International Conference and Workshop on Modeling Consequence of Accidental Releases of Hazardous Materials, San Francisco, CA, USA, 97-130 (September/October 1999).
B7. Cleaver, R.P., Buss, G.Y., Tam, V., Connolly, S., Britter, R.E. Gas build-up from high pressure natural gas releases in naturally ventilated offshore modules. Proceedings, 7th Annual Conference on Offshore Installations: Hazard Management and Fire and Explosion Engineering (December 1998). Published in: ERA report 98-0958 (ERA Technology Ltd, Leatherhead, 1998).
B8. Daish, N.C., Britter, R.E., Linden, P.F., Jagger, S.F., Carissimo, B. SMEDIS: scientific model evaluation techniques applied to dense gas dispersion models in complex situations. Proceedings, International Conference and Workshop on Modeling Consequence of Accidental Releases of Hazardous Materials, San Francisco, CA, USA, 345-371 (September/October 1999).
B9. Dawes, W.N. Challenges for turbomachinery CFD in the 21st century. (Invited Lecture). 1st International Conference on Engineering Thermophysics (ICET'99), Beijing, China (August 1999).
B10. Denton, J.D., Dawes, W.N. Computational fluid dynamics for turbomachinery design. Proceedings of the Institution of Mechanical Engineers, Part C, Journal of Mechanical Engineering Science, 213, (C2), 107-124 (1999).
B11. Graham, W.R. Asymptotic analysis of the classical aircraft stability equations. Aeronautical Journal, 103, (1020), 95-103 (February 1999).
B12. Graham, W.R., Peraire, J., Tang, K.Y. Optimal control of vortex shedding using low-order models. Part I - open-loop model development. International Journal for Numerical Methods in Engineering, 44, (7),
B13. Graham, W.R., Peraire, J., Tang, K.Y. Optimal control of vortex shedding using low-order models. Part II - model-based control. International Journal for Numerical Methods in Engineering, 44, (7), 973-990 (1999).
B14. Hankin, R.K.S., Britter, R.E. TWODEE: the Health and Safety Laboratory's shallow layer model for heavy
gas dispersion. Part I, mathematical basis and physical assumptions. Journal of Hazardous Materials, 66, (3), 211-226 (1999).
B15. Hankin, R.K.S., Britter, R.E. TWODEE: the Health and Safety Laboratory's shallow layer model for heavy gas dispersion. Part 2, outline and validation of the computational scheme. Journal of Hazardous Materials, 66, (3), 227-238 (1999).
B16. Hankin, R.K.S., Britter, R.E. TWODEE: the Health and Safety Laboratory's shallow layer model for heavy
gas dispersion. Part 3: experimental validation (Thorney Island). Journal of Hazardous Materials, 66, (3),
B17. Inger, G.R., Babinsky, H. Viscous compressible flow across a hole in a plate. Proceedings, 17th AIAA Applied Aerodynamics Conference, Norfolk, VA, USA, AIAA Paper 99-3191 (June/July 1999).
B18. Kellar, W.P., Savill, A.M., Dawes, W.N. Integrated CAD/CFD visualisation of a generic formula 1 car front wheel flowfield. High Performance Computing and Networking: Proceedings, 7th International Conference, HPCN Europe 1999, Amsterdam, the Netherlands (April 1999); Edited by P. Sloot, et al. Lecture Notes in Computer Science 1593 (Springer-Verlag, 1999).
B19. Lingwood, R.J. Book review: Hydrodynamics and Nonlinear Instabilities; edited by C. Godrèche, P. Manneville, Cambridge University Press, 1998. Journal of Fluid Mechanics, 380, 377-378 (1999).
B20. Lingwood, R.J. On the application of en-methods to three-dimensional boundary-layer flows. European Journal of Mechanics-B/Fluids, 18, (4), 581-620 (1999).
B21. Lingwood, R.J., Alfredsson, P.H. Experimental study of the stability of the Bödewadt layer. Proceedings, IUTAM Symposium on Laminar-Turbulent Transition, Sedona, AZ, USA (September 1999).
B22. Nickels, T.B., Joubert, P.N. Separation in a rotating diffuser. Proceedings, 13th Australasian Fluid Mechanics Conference, Melbourne, Australia; Edited by M.C. Thompson, K. Hourigan, 2, 769-771 (December 1998).
B23. Sandham, N., Savill, A.M., Dawes, W.N. Direct numerical simulation and modelling of turbulence in trailing edge flows. Proceedings, Royal Aeronautical Society University Days Meeting, London (January 1999).
B24. Savill, A.M. ERCOFTAC SIG 10 - transition modelling: update report. Proceedings, Isaac Newton Institute for Mathematical Sciences and ERCOFTAC Workshop on Breakdown to Turbulence and its Control, Cambridge
B25. Savill, A.M. SIG 10 - transition modelling. ERCOFTAC Bulletin, 41, 30-31 (June 1999).
B26. Savvides, C., Tam, V., Cleaver, R.P., Darby, S., Buss, G.Y., Britter, R.E., Connolly, S. Gas dispersion in a congested, partially confined volume. Proceedings, International Conference and Workshop on Modeling Consequence of Accidental Releases of Hazardous Materials, San Francisco, CA, USA, 435-456 (September/October 1999).
B27. Sinclair, F.M., Birkby, P., Savill, A.M., Dawes, W.N. Flow visualisation and animation using results from flow analyses. Prooceedings, Eurographics UK 17th Annual Conference, Cambridge (April 1999).
B28. Sinclair, F.M., Dhanasekaran, P.C., Demargne, A.A.J., Dawes, W.N., Savill, A.M. From CAD to CFD - interior volume removal as a data conversion tool. Proceedings, Eurographics UK 17th Annual Conference, Cambridge (April 1999).
B29. Sleath, J.F.A. Conditions for plug formation in oscillatory flow. Continental Shelf Research, 19, (13), 1643-
B30. Sleath, J.F.A. Plugs and plumes. Coastal Ocean Processes Symposium, Woods Hole, MA, USA, 211-215 (September 1998). Published as: Woods Hole Oceanographic Institution Technical Report WHOI-99-04 (1999).
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Last modified: June 2000