The Bow in the NASA Langley Mach 6 quiet wind tunnel has been investig
ated to quantify the effectiveness of laminar-flow control techniques
used to delay transition of the nozzle-wall boundary layer, The result
s of this investigation include an assessment of the mean and unsteady
nozzle flow to define the quiet core length, and hence performance, o
ver the operating range of the facility, A large, uniform region of Ma
ch 5.91 flow was documented for a variety of unit Reynolds numbers. By
using a prototype constant-voltage anemometer to measure the unsteady
flowfield, acoustic radiation patterns from the transitional nozzle w
all boundary layers were mapped, These disturbances originating at the
irregular edge of the transitional nozzle-wall boundary layer were sh
own to follow Mach lines into the test section of the nozzle, thereby
limiting the length of the quiet core, With a virtual origin downstrea
m of the nozzle throat, a Reynolds number dependency was found for the
amplitudes of the acoustic radiation, The spectral evolution of noisy
Bow in the quiet tunnel was shown, and measurable freestream disturba
nces, outside the region of quiet flow, were found to be qualitatively
similar to those documented for conventional high-speed tunnels. In s
um, the laminar-flow control techniques used to delay nozzle-wall boun
dary layer transition in the Mach 6 nozzle test chamber facility have
succeeded in producing a substantial region of quiet flow suitable for
high-speed boundary layer stability research.