Department of Engineering - Annual Report 1997/98

Fluid Mechanics

Fluid Mechanics
Compressible Aerodynamics
Flow Noise
Environmental Fluid Dynamics
Computational Fluid Dynamics
Coastal Engineering

References

Fluid Mechanics

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 is starting to link up with CFD activity in this area. 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. Big contributions are being made, via the European Commission, to debates on environmental concerns. Sediment transport in coastal engineering continues to be studied in our range of flumes, funded in part by EPSRC. The CFD laboratory is now recognised as a centre of excellence by both aerospace and the oil and gas industry.

Compressible Aerodynamics

The effect of suction on shock/boundary layer interactions in transonic and supersonic flow is currently
investigated. The aim of this research is to reduce drag and improve aerofoil performance for transonic aircraft. This work is supported by the European Commission as part of the Euroshock II programme. Further work has been initiated to investigate roughness effects on turbulent shock/boundary layer interactions.

Earlier experimental and theoretical studies into shock angles on delta wings(B12) and shock wave focusing(B2) have now been published. Also published this year is a major review of the role of high speed wind tunnels in aeronautical research(B17).

Flow Noise

Research into the generation of noise by the flow past engineering structures has continued. This is a significant source of sound both inside and outside passenger aircraft, and is also becoming important in trains as their speeds increase. The phenomenon is caused by the unsteady pressure forces on the surface of the structure. A number of mathematical models for these forces exist, but there is currently little agreement as to which should be used. To this end, a comparison study investigating the influence of the choice of model on the predictions of interest has been carried out(B9).

Another feature which is still incompletely characterised is the influence of the external flow(B11) on the acoustic field(B10), and hence on the structural vibration. Existing analytical results for the acoustic field on a finite plate have been extended to take account of the flow speed, providing valuable insight into the physical effects involved.

Environmental Fluid Dynamics

Three themes have continued, all associated with the European Commission. Monitoring strategies for urban air quality in European cities were compiled and reported(B5). A book was published for the European Commission overviewing research on the dispersion of hazardous material and placing the Commission's research programme in a broader context(B7). The importance of formalised evaluation of the quality (fitness-for-purpose) of technical models used for urban air quality studies has been considered; in particular they are used for regulatory purposes(B6) and collaborative work has resulted in reports on dense gas dispersion(B8).

Computational Fluid Dynamics

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 (like concrete). Our core competence lies in the ability to draw on fundamental modelling using DNS and LES in both combustion(A23,A24,A37,A38) and turbulence/transition(B1) to improve practical, Reynolds averaged models(A39,B3,B4,B13) and then apply this to real problems via state of the art unsteady, solution-adaptive, flow simulation in complex geometries(A4,A5,B14,B15,B19). 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*).

Coastal Engineering

Work has continued on the investigation of sediment transport under severe wave conditions. A model has been derived for the thickness of the mobile layer and the results presented at a conference in Copenhagen(B16). Measurements have been made of the velocity and concentration profiles in the mobile layer of sediment and the results published(B19).

The effect of sediment movement on turbulence intensity and bed friction has been studied in an oscillatory flow water tunnel and the results published(B20).

Work has started on an investigation funded by EPSRC into the entrainment of sediment from rippled beds.

B1. Alam, M., Avital, E., Craft, T.J., Fiddes, S.P., Horton, H.P., Howard, R.J.A., Jones, D.P., Luo, K.H., Sandham, N.S., Savill, A.M., Thomas, T.G., Voke, P.R., Williams, J.J.R. Understanding turbulence in fluids using direct simulations data. Proceedings, HPCI98, High Performance Computing Initiative Conference, Manchester (January 1998).

B2. Babinsky, H., Onodera, O., Takayama, K., Saito, T., Voinovich, P., Timofeev, E. Influence of entrance geometry of circular reflectors on shock wave focusing. Computers and Fluids, 27, (5/6), 611-618 (1998).

B3. Biesinger, T.E., Savill, A.M. Non-equilibrium and non linear k-e model contribution to ERCOFTAC Test Case No.3 . Proceedings, 6th ERCOFTAC Seminar and Workshop on Turbomachinery Flow Predictions, Aussois, France (January 1998).

B4. Biesinger, T.E., Savill, A.M., Coupland, J. Refined k-e turbulence model Q3D-predictions in compressor cascades at design and off-design. Proceedings, ASME International Gas Turbine and Aeroengine Congress and Exhibition, Stockholm, Sweden, ASME Paper 98-GT-322 (June 1998).

B5. Bozo, L., Carratala, D., Millan, M.M., Palmgren, F., Arend, M., Britter, R.E. Urban Air Quality Monitoring Strategies and Objectives in European Cities. (European Commission DG XII, 1998).

B6. Britter, R.E. The evaluation of model quality. COST CITAIR Newsletter (European Commission DG XII), 1/98, 6-7 (1998).

B7. Britter, R.E. Recent Research on the Dispersion of Hazardous Materials. EUR 18198 (European Commission, 1998). ISBN 92-828-3048-9

B8. Daish, N.C., Britter, R.E., Linden, P.F., Jagger, S.F., Carissimo, B. SMEDIS: Scientific model evaluation of dense gas dispersion models. Proceedings, 5th International Conference on Harmonisation with Atmospheric Dispersion Modelling for Regulatory Purposes, Rhodes, Greece ( May 1998).

B9. Graham, W.R. A comparison of models for the wavenumber-frequency spectrum of turbulent boundary-layer pressures. Journal of Sound and Vibration, 206, (4), 541-565 ( 1997).

B10. Graham, W.R. The effect of mean flow on the radiation efficiency of rectangular plates. Proceedings of the Royal Society of London, Series A, Mathematical, Physical and Engineering Sciences, 454, (1968),111-137 ( 1998).

B11. Graham, W.R. Review of `Fluid dynamics for physicists', by T.E. Faber, Cambridge University Press, 1995. Journal of Fluids and Structures, 11, (7), 855-856 ( 1997).

B12. Koide, S., Loria, A.F., Babinsky, H. Prediction of shock angles caused by sharp delta wings with attack angle. AIAA Journal, 36, (7), 1327-1328 ( 1998).

B13. Savill, A.M. ERCOFTAC SIG 10 - Transition Modelling update report. ERCOFTAC Bulletin, 37, 33 ( June 1998).

B14. Sinclair, F.M., Birkby, P.J., Savill, A.M., Cant, R.S., Dawes, W.N. Numerical flow visualisation using results from an unstructured adaptive mesh. Proceedings, 8th International Symposium on Flow Visualisation, Sorrento, Italy, 3.1-3.7 ( September 1998).

B15. Sinclair, F.M., Connell, I.J., Bray, K.N.C., Savill, A.M. Investigations of using computer aided design and virtual reality to enhance CFD for complex environmental flow. Proceedings, Engineering Applications of Computational Fluid Dynamics Theme Day, EPSRC, London ( May 1998).

B16. Sleath, J.F.A. Depth of erosion under storm conditions. Proceedings, 26th Conference on Coastal Engineering, Copenhagen, Denmark ( June 1998).

B17. Squire, L.C. A review of the role of some small high-speed wind tunnels in aeronautical research. Progress in Aerospace Sciences, 34, (3-4), 107-166 ( 1998).

B18. Watterson, J.K., Connell, I.J., Savill, A.M., Dawes, W.N. An solution-adaptive mesh procedure for predicting confined explosions. International Journal for Numerical Methods in Fluids, 26, (2), 235-247 ( 1998).

B19. Wijetunge, J.J., Sleath, J. F.A. Effects of sediment transport on bed friction and turbulence. Journal of Waterway Port Coastal and Ocean Engineering (ASCE), 124, (4), 172-178 ( 1998).

B20. Zala Flores, Z., Sleath, J.F.A. Mobile layer in oscillatory sheet flow. Journal of Geophysical Research, 103, (C6), 12783-12786 ( 1998).

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Last modified: October 1999