The 17-meter flume at the Coastal Research Laboratory. Part II, Flow characteristics : technical report

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Date
1989-05Author
Trowbridge, John H.
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Geyer, W. Rockwell
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Butman, Cheryl Ann
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Chapman, Robert J.
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https://hdl.handle.net/1912/6413DOI
10.1575/1912/6413Keyword
Hydraulic models; TurbulenceAbstract
This report summarizes the characteristics of the idealized one-dimensional turbulent
channel flow for which the 17-Meter Flume was designed, and describes a measurement program
designed to determine whether the flume can in fact produce such a flow. The measured
quantities include mean velocities, Reynolds stresses, turbulence intensities and velocity spectra.
Measured profiles of mean velocity, Reynolds stress and turbulence intensity are consistent
with previous theoretical and empirical results. Measured spectra, although consistent
with expectations over a wide range of frequencies, indicate a few unexpected features, including
a constant spectral density at high frequencies (possibly due to aliasing or high-frequency
noise) , motion at a few well-defined high frequencies of order 10 hz (possibly due to structual
vibrations), oscillations with time scales of order 30 s (possibly due to low-mode standing
surface waves) and irregular motions with time scales of several minutes (possibly due to
fluctuations in pump performance) . The unexpected features indicated by the spectra at
high and low frequencies do not have a significant effect on mean velocities and low-order
statistics, but they may be important in some applications.