Projects: Projects for Investigator |
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Reference Number | EP/F045093/1 | |
Title | Streak Instability and Bypass Transition | |
Status | Completed | |
Energy Categories | Energy Efficiency(Transport) 2%; Not Energy Related 90%; Other Power and Storage Technologies(Electric power conversion) 5%; Energy Efficiency(Industry) 3%; |
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Research Types | Basic and strategic applied research 100% | |
Science and Technology Fields | PHYSICAL SCIENCES AND MATHEMATICS (Applied Mathematics) 35%; ENGINEERING AND TECHNOLOGY (Mechanical, Aeronautical and Manufacturing Engineering) 65%; |
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UKERC Cross Cutting Characterisation | Not Cross-cutting 100% | |
Principal Investigator |
Dr X Wu No email address given Mathematics Imperial College London |
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Award Type | Standard | |
Funding Source | EPSRC | |
Start Date | 15 December 2008 | |
End Date | 14 June 2012 | |
Duration | 42 months | |
Total Grant Value | £353,257 | |
Industrial Sectors | Aerospace; Defence and Marine | |
Region | London | |
Programme | NC : Engineering | |
Investigators | Principal Investigator | Dr X Wu , Mathematics, Imperial College London (99.998%) |
Other Investigator | Dr T Zaki , Department of Mechanical Engineering, Imperial College London (0.001%) Professor SJ Sherwin , Aeronautics, Imperial College London (0.001%) |
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Web Site | ||
Objectives | ||
Abstract | Laminar-turbulent transition is a fundamental problem in fluid mechanics that has great implications for the prediction of drag, aerodynamic heating, and flow separation. For example, transition to turbulence can bypass flow separation in compressors, and in the low-pressure-turbine stage, 50% of the flow can be transitional. While the end-state may always be an equilibrium turbulent boundary layer, transition itself can be mediated by different mechanisms and each results in distinctly different transition locations and lengths.The literature generally divides transition scenarios into the natural, or orderly, route and the bypass mechanism. The former is characterized by viscous Tollmien-Schlichting (T-S) instability waves which can be observed experimentally under quiet testing conditions. In the presence of free-stream disturbances, which are loosely referred to as free-stream turbulence (FST), transition takes place more swiftly, thus bypassing the natural route, and hence the term "bypass transition".In the bypass mechanism, elongated high-amplitude disturbances, known as boundary layer streaks, are observed in the pre-transitional region of the flow. Breakdown has been attributed to a secondary instability of these streaks, but the exact dependence has only been speculated and never satisfactorily quantified. The proposed research is first to accurately and efficiently compute the non-linear streaks by using a combined theoretical and numerical approach. We will also analyze the stability of these streaks, and our study will provide an estimate for the required threshold of free-stream disturbances for streak instability. It will also give a quantitative relation between the location where the streaks first become unstable and the intensity of the free-stream disturbances. Such information will be useful for the design of airfoils which operate in transitional flow regimes | |
Publications | (none) |
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Final Report | (none) |
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Added to Database | 17/03/08 |