鉛直円管内上昇気泡流における乱流エネルギ輸送機構の解明(混相(3),一般講演)

概要

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Particle tracking velocimetry (PTV) with Sub-Kolmogorov time and spatial resolution was used to investigate the mechanisms of turbulence modification by dispersed bubbles in an upward bubbly pipe flow. Experiments were conducted for two different bubble diameters of 1.7mm and 2.6mm. Void fraction, α, was set to be 0.5%, 1.0%, or 1.5%. A Reynolds number based on the pipe diameter and mean velocity was 9,900. Since bubbles were accumulated near the wall region and accelerated the fluid, the mean flow profiles were flattened. The flattened mean velocity suppressed the turbulence intensities. By utilizing the spatial filtering technique, we characterized the length scales that govern the energy transfer between bubbles and turbulence. Strong energy transport from bubbles can be clearly observed at the scale of from two to three times the bubble diameter, indicating the interactions between bubbles and the fluid are predominant at this scale.
2008-09-04