102 回転二重円筒内の微小気泡運動と抵抗低減(2)(OS1-1 流れの抵抗低減,OS1 流れの抵抗抵減,オーガナイズドセッション)

概要

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Relationship between drag reduction and microbubble motion in a vertical Taylor-Couette flow is investigated by visualization of r-z cross section. We have measured the vorticity distribution in two-phase condition by means of particle tracking velocimetry (PTV). The bubble distribution shows two modes as Re number changes, i.e. toroidal and spiral modes. In low Re number region, the vortex structure is modified significantly by the bubbles. The presence of bubbles provides elongation of vortical wavelength to be around 1.5 times as that without bubbles. This alternation of the cell yields a large reduction ratio of the shear stress in low Re number region while the drag reduction effect is weakened as Re number increases for the high kinetic energy of the cell motion.
2007-11-17