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DRAG FLUCTUATIONS ON DEFORMED BUBBLES IN A TURBULENT SHEAR FLOW BY MEANS OF DNS

Yoshinobu Yamamoto
Department of Nuclear Engineering, Kyoto University, Yoshida Sakyo-ku, Kyoto 606-8501,Japan

Tomoaki Kunugi
Department of Nuclear Engineering, Kyoto University, Kyoto Daigaku-Katsura, Nishikyo-ku, Kyoto, Japan

Kazuyuki Takase
Japan Atomic Energy Agency

Résumé

In this study, the direct numerical simulation of a fullydeveloped turbulent channel flow with deformed bubbles were conducted by means of the MARS method, turbulent Reynolds number 150, and Particle Reynolds number 120. As the results, large scale wake motions round bubbles were confirmed. At the bubble related region, mean velocity was degreased and turbulent intensites and Reynolds shear stress were incresed by the effects of the large scale wake motions round bubbles. On the other hands, near wall region, effects of bubbly flow might act on flow laminarlize and drag reduction.
Two types of drag coefficient of bubble were estimated from the accelerated velocity of bubble and experimental equation as a function of Particle Reynolds number. Drag coefficient estimated by the accelerated velocity of bubble was below the results estimated by the experimental equation.