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National Advisory Committee for Aeronautics, Technical Notes - Turbulence Intensity Measurements in a Jet of Air Issuing from a Long Tube

Data are presented for turbulent—vslocity-fluctuation components
and mean—velocity distributions measured in the subsonic jet issuing
from a pipe in which fully‘developed turbulent flow was established.
Boundary conditions were set by mounting this pipe concentrically with
a larger pipe and maintaining the maximum velocity in the resulting
annulus equal to the mean velocity in the inner pipe.

Axial and radial components of the fluctuation velocities were
examined as functions of Reynolds number and position in the jet. The
dimensionless velocity profiles varied only slightly with varying Reynolds
number. The ratios of the root~mean-square axial turbulent fluctuation
velocities to the local mean velocities shOWed a slight increase with
increasing Reynolds numbers. The radial components of the fluctuation-
velocity parameter showed no systematic variation with Reynolds number.

The turbulence was not isotropic in the jet formed by the inner -
pipe. The axial-fluctuation-velocity component was approximately
2.5 times as great as the radial component at the pipe center line.,
Near the pipe wall at the exit survey station, the axial- fluctuation-
velocity component was about 3 or A times as great as the radial
component.

The axial components of the turbulent fluctuation velocities
diminish rapidly directly downstream of the pipe wall, whereas the radial
components are practically constant, so that the axial and radial com-
ponents approach a condition of equal magnitude with increasing distance
from the pipe exit.

An investigation of the flame-propagation properties in burners by
the Bureau of Mines of the United States Department of Interior has
indicated that, for the correlation of the flame-propagation velocities
with local turbulence intensity in the flow, quantitative turbulence
data are needed. In order to obtain such data, an experimental investi-
gation has been made at the Langley.Aeronautical Laboratory of the
National Advisory Committee for Aeronautics for a configuration closely
resembling that of the Bureau of Mines.