Journal
FLOW TURBULENCE AND COMBUSTION
Volume 89, Issue 4, Pages 547-562Publisher
SPRINGER
DOI: 10.1007/s10494-012-9407-y
Keywords
Separated-flow transition; Kelvin-Helmholtz instability; Loss production mechanisms; Deformation work; Ultra-high-lift turbine blade profile
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Funding
- European Commission
- Italian Ministry for Instruction, University and Research
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The present paper reports the results of a detailed experimental study, carried out by means of a two-component Laser Doppler Velocimeter, aimed at investigating the loss generation mechanisms induced by laminar separation bubble and transition process. Measurements have been performed along a flat plate installed within a double contoured test section, designed to produce an adverse pressure gradient typical of Ultra-High-Lift turbine blade profiles, which induces the formation of a laminar separation bubble. Results were detailed enough to allow calculating laminar and turbulent deformation works in the separated flow region. Normal and shear contributions of both viscous and turbulent deformation works have been analyzed and employed to explain the generation of total pressure losses in the separated flow region, where the generation and amplification of Kelvin-Helmholtz instability induces the separated shear layer roll-up, thus the bubble reattachment. Results obtained for different Reynolds number conditions have been employed for the formulation of a loss scaling procedure involving the separated shear layer thickness, which is directly correlated to the dynamics of Kelvin-Helmholtz roll-up vortices.
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