0224 振動格子減衰乱流と気泡群が誘起する流れ場の相互干渉により生じる液相速度変調(OS2-5 乱流の計測・解析・制御,オーガナイズドセッション)

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The objective of this study is to clarify turbulence modulation induced by interaction between a bubble swarm and decay process of oscillating-grid turbulence. First, homogeneous isotropic turbulence was formed by operating oscillating-grid in cylindrical acrylic pipe filled with ion-exchanged and degassed water. Second, we stopped the oscillating-grid in arbitrary time after the homogeneous isotropic turbulence was achieved. A few moments later, the controlled bubble swarm (number of bubbles: 3, equivalent bubble diameter: 3mm, bubble Reynolds number: 859, Weber number: 3.48) was launched into the decaying turbulence. The bubble formation, bubble size and bubble-launch timing are controlled arbitrarily and precisely. The bubble and liquid motion was captured by high-speed video camera and PIV measurement. The liquid-phase ambient turbulence enhanced transition of the bubble motion from zigzag motion to spiral motion. The decay-rate of the turbulence was increased via interaction between the buoyancy flow induced by the bubble swarm and liquid-phase turbulence.
2009-11-06