TED-AJ03-198 THE MODIFICATION OF TURBULENCE STRUCTURE IN BUBBLY PIPE FLOW : EFFECT OF VOID FRACTION AND BUBBLE DIAMETER

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概要

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• The objective of present study is to elucidate the mechanism of modification of turbulence structure in gas-liquid bubbly flow. Many research on turbulent bubbly flows indicated that the turbulence augmentation and the reduction strongly depend on their void fraction and the distribution of bubble size. In order to obtain fundamental knowledge of the effects of void fraction and bubble diameter on modification of turbulence structure experimentally, we explored the two-dimensional flow structure in the vicinity of bubbles by applying PIV with fluorescent tracer particles. Also bubble shapes and positions were obtained by projecting shadow-image technique. The experiment consisted of a vertical upward pipe flow with 0.5 and 1.0% of void fraction. The pipe diameter 2R is 44mm and Re number is 9700. In order to compare the effect of the bubble diameter in same void fraction, nearly 60ppm of 3-Pentanol (C_5H_<11>OH) are added as the surfactant. Moreover, to avoid optical distortion by refraction of pipe, we applied FEP pipe, the[figure] refractive index of FEP is approximately the same as that of water, in test section. Figure A-1 shows the instantaneous vorticity contours in the case of α=0.5% in both with and no surfactant fluid. Gray spots denote bubbles, and they accumulated in the vicinity of the wall (γ/R=1.0). And they accelerated the mean streamwise velocity near the wall as shown in Figure A-2. Thus mean streamwise velocity profile became flat. Moreover, the streamwise fluctuation velocity suppressed. It is suggested that the high concentrated bubbles in the vicinity of the wall disturb the transport of turbulence energy produced by the wall shear layer toward the middle of pipe. Thus the fluctuation velocity is remarkably reduced at the wide region of the pipe center. Moreover, in the middle of channel, the turbulence structure is governed by pseudo-turbulence induced by present bubbles.[figure]

著者

• Hishida Koichi

  Dept. Of System Design Engineering Keio University

• Hishida Koichi

  Dept. Of Mech. Engng. Keio University

• Tanaka Tomohiko

  Dept. Of System Design Engineering Keio University

• MAEDA Masanobu

  Dept. of Mech. Engng., Keio University

• MINATO Daiju

  Dept. of System Design Engineering, Keio University

• FUJIWARA Akiko

  Dept. of Mechanical Engineering, The University of Tokyo

• Minato Daiju

  Dept. Of System Design Engineering Keio University

• Maeda Masanobu

  Dept. Of System Design Engineering Keio University

• Maeda Masanobu

  Dept. Of Mech. Engng. Keio University

• Fujiwara Akiko

  Dept. Of Mechanical Engineering The University Of Tokyo

関連論文

• TED-AJ03-198 THE MODIFICATION OF TURBULENCE STRUCTURE IN BUBBLY PIPE FLOW : EFFECT OF VOID FRACTION AND BUBBLE DIAMETER
• Feedback Control of Heat Transfer by Impinging Planar Two Jets Array : Controller Tuning Based on Simultaneous Measurements of PIV/Heat Transfer
• Development of Fibre LDV and Measurements of Turbulence in Boundary Layer on a Flat Plate

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