Hole Exit TI Measurements in Film Cooling Flows
The local turbulence intensity profiles at hole exit are also found to
be highly sensitive to the film cooling length. In general, high
coolant momentum correlates to low local turbulence. Film cooling
with short holes (L/D=2.3 in figures) tends to have a great deal of
its coolant mass distributed towards the upstream portion of and along
the edges of the hole at the exit plane. In general, local turbulence
levels in these regions are lowest. Film cooling through long lengths
(L/D=7.0 in figures) though is characterized by more uniform profiles
or those slightly favoring the downstream portion of the hole at exit.
Local turbulence levels are lowest in high-coolant-momentum regions.
All film cooling flows tend to have a large region of very high
turbulence levels upstrem of the hole. These high levels (~50%)
correspond to the coolant-freestream stagnation region. Precise
turbulence levels over the hole exit, though, depend on the
coolant-to-freestream blowing rates. Hole exit local turbulence
intensity (u'/Ulocalx100) profiles for film cooling through short and
long lengths (L/D=2.3 and 7.0) and at low and high (VR=0.5 and 1.0)
blowing rates are provided below.
Low Blowing Rate (VR=0.5):
High Blowing Rate (VR=1.0):
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