| Budget Amount *help |
¥10,200,000 (Direct Cost: ¥10,200,000)
Fiscal Year 2000: ¥4,800,000 (Direct Cost: ¥4,800,000)
Fiscal Year 1999: ¥5,400,000 (Direct Cost: ¥5,400,000)
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| Research Abstract |
One of the most important aspects of dispersed two-phase flow is the interaction of dispersed phase with turbulent flow, which controls the performance of many engineering devices. In gas-liquid two-phase flow many experimental evidence indicated that the turbulent intensity became decreased or increased according to dependence on the void fraction and gas flow rate. However the mechanisms of turbulent modulation by bubbles are still unexplored, especially microstructure of the interaction between bubbles. The objective of the present study is to elucidate the mechanism of interaction of bubbles and microstructure of turbulence and heat and mass transfer process in dispersed two-phase flow. Experiments have been performed on turbulent microstructures in a simple shear layer flow involving a single rising bubble, an upward bubbly channel flow. Velocity measurements were made using one digital high-speed CCD camera for Digital Particle Image Velocimetry (DPIV) with fluorescent tracer particles (PIV/LIF). The recorded image data were analyzed by cross-correlation technique. A second CCD camera was used to detect the bubble's shape and translational motion via backlighting from a square array of infrared LED's (Infrared Shadow Technique IST). We clarified turbulent structures of surrounding fluid that was influenced by the bubble motion, quantitatively measured by PIV/LIF/IST technique. For the experiments of single bubble in shear layer, we estimated various forces on the bubble, bubble trajectory, and the interactive influence on flow structure. Further more, in upward bubbly channel flow, it can be seen that when the void fraction was low vorticities appeared in the vicinity of the bubble individually, while when the void fraction was high value of vorticities appeared in inter-particle spacing. These experimental results have been related to detailed mechanism of transport phenomena in bubbly turbulent flows.
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