As part of the collaborative NASA/industry/academia Low Pressure
Turbine (LPT) Flow Physics program, smoke flow was visualized
from a simulated low-pressure turbine experiment in NASA Lewis
Research Center's CW-7 test facility. As shown in the photographs,
a laminar separation bubble formed on the bottom flat surface.
This is characteristic of the flows in a large-scale, low-pressure
turbine operating under off-design conditions. A contoured upper
wall was designed to generate a pressure distribution on a flat
plate to match the suction surface pressure distribution from
a generic low-pressure turbine blade.
This photograph was taken from a 2-sec burn of smoke from a smoke-wire
generator located upstream of the test section. At the time, the
Reynolds number was 90,000 (based on exit velocity) and the free-stream
turbulence intensity was 0.7 percent. The photograph helped to
validate the existence and axial location of the separation bubble
and provided qualitative features of the bubble such as the large
eddy structures in its trailing edge region.
Previous articleLast updated May 6, 1997
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