Butman Cheryl Ann

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Technical Report

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

1989-05 , Trowbridge, John H. , Geyer, W. Rockwell , Butman, Cheryl Ann , Chapman, Robert J.

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.

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Technical Report

The 17-meter flume at the Coastal Research Laboratory. Part I, Description and user's manual : technical report

1989-05 , Butman, Cheryl Ann , Chapman, Robert J.

The 17-Meter Flume, a recirculating, temperature-controlled, seawater channel, was recently constructed in W.H.O.I.'s Coastal Research Laboratory for studies of boundary-layer flows and sediment transport, and for interdisciplinary research where adequate simulation of the near-bed flow environment is required. The flume channel is 17.3-m long by 0.6-m wide and can be filled to a maximum depth of 0.3 m. The water is circulated by a centrifugal pump and is temperature controlled to ± 0.5°C over a range of about 4-30°C. Made of fiberglass , glass, plastics and high-grade stainless steel, all surfaces of the flume that come into contact with the water are noncorrosive and nontoxic to organisms. The flume is equipped with a computer-controlled, two-axis, laser-Doppler velocimeter (LDV) for detailed, accurate and precise measurements of flow characteristics anywhere along the flume channel. In addition to detailed descriptions and illustrations of all components of the flume, this report provides instructions for use of the flume and associated instrumentation. In Part II, flume flow characteristics measured with the LDV are illustrated and evaluated relative to theoretical and empirical expectations for open-channel flows.

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