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Experimental Investigation of Unsteady Transition Processes on High-Lift T106A Turbine Blades
Periodic wake-boundary layer interactions on the T106A high-lift low-pressure turbine blade cascade at engine-representative flow conditions are described. Through a comparison with previously published moderate Reynolds number/low freestream turbulence data, the influence of elevated freestream tur...
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Published in: | Journal of propulsion and power 2008-05, Vol.24 (3), p.424-432 |
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Main Authors: | , |
Format: | Article |
Language: | English |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | Periodic wake-boundary layer interactions on the T106A high-lift low-pressure turbine blade cascade at engine-representative flow conditions are described. Through a comparison with previously published moderate Reynolds number/low freestream turbulence data, the influence of elevated freestream turbulence intensity and Reynolds number is assessed and the following conclusions are drawn. At elevated freestream turbulence, the mechanism of turbulence production outside of the boundary layer did not change. Although, an enhanced diffusion of turbulence in the wake was responsible for small decreases in the maximum value of the turbulent kinetic energy in the freestream. For both freestream turbulence cases, the wake from upstream interacted with the inflexional or separated shear layer and forced an inviscid Kelvin-Helmholtz type of breakdown, resulting in the formation of roll-up vortices. At corresponding Reynolds numbers, the turbulence in the wake induced a bypass transition, at a similar streamwise location and phase of the unsteady wake interaction cycle. Furthermore, the higher freestream turbulence delayed the appearance of the inflexional profiles in space, and the transition onset occurred farther upstream. The latter is related with the effect of changes in the Reynolds number. Reduced Reynolds numbers extended the length of the inflexional shear layer, resulting in the formation of a greater number of vortices. Furthermore, the delayed transition allowed these vortices to penetrate farther downstream. Increasing the Reynolds number, at the higher freestream turbulence level, led to the limiting case, where roll-up vortices were not seen to be formed. [PUBLISHER ABSTRACT] |
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ISSN: | 0748-4658 1533-3876 |
DOI: | 10.2514/1.31947 |