Turbulence structure resulting from interaction between an embedded vortex and wall jet.
Green, James G.
Subramanian, Chelakara S.
Ligrani, Phillip M.
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Interactions of wall jets and vortices embedded in turbulent boundary layers commonly occur near gas turbine blades and endwalls where film cooling is employed. These interactions frequently result in undesirable heat transfer effects at blade and endwall surfaces. In this research, a crossed hot-wire probe is used to measure the turbulence structure resulting from this type of interaction. The vortex is generated using a half-delta-wing vortex generator mounted at 12 degrees with respect to a 10 m.'s mean velocity flow over a flat plate. A single injection hole, .95 cm in diameter, inclined 30 degrees to the horizontal, is located under the vortex downwash, 58 cm downstream from the vortex generator. Baseline measurements were made at one streamwise location downstream of the injection hole for the cases: (1) boundary layer only, (2) boundary layer with vortex, and (3) boundary layer with wall jet. Measurement of the interaction between the boundary layer, vortex and 2.5 blowing ratio wall jet was also made at this location. The 1.5 blowing ratio wall jet interaction was measured at three additional streamwise locations. Reynolds stress tensor components, vorticity distributions and mean velocities show that the vortex significantlv alters the turbulence structure of the 1.5 blowing ratio wall jet at all lour streamwise locations. Here the injectant is swept away from the injection hole by the vortex rotation. The most significant alterations to the turbulence structure occur in the vortex upwash region and beneath the vortex core. The 2.5 blowing ratio jet is much more resistant to disturbance by the vortex.
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