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EFFECT OF BUBBLE DIAMETER ON MODIFICATION OF TURBULENCE IN AN UPWARD PIPE FLOW

Akiko Fujiwara
Intelligent Modeling Laboratory, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan

Daiju Minato
Department of System Design Engineering, Keio University, Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan

Koichi Hishida
Department of System Design Engineering, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, 223-8522

Abstract

The objective of the present study is to elucidate the effect of dispersed bubble size on turbulence modification in vertically upward driven bubbly pipe flow. The experiment was conducted with void fractions of 0.5 and 1.0%. Liquid phase velocity is measured by particle image velocimetry with fluorescent tracer particles (PIV/LIF). Bubbles' size and velocity are estimated from the bubbles' image observed by projecting shadow image technique. Bubbles strongly accumulate near the wall and slide up. The high concentration of bubbles in the vicinity of the wall induce reduction of fluctuation velocity intensity. The effect of bubble-induced turbulence on the global pipe flow structure was discussed with the turbulent energy production and dissipation are estimated from experimental data, and local vortical structure around the bubbles.