Design Problem on Bubble Occurrence for Complex Lequid Jet Flow

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1. The measurement of nuclei distribution was conducted with Coulter counter under various conditions in bubble occurrence experiments. The air content was measured with Numachi's method and compared with the nuclei concentration. Next, the dissolved oxygen in water was measured with D. O. meter and compared with the air content. The measurement method of the water quality was established through these process.2. The bubble occurrence phenomena in jet flow are stochastic and random because the measurement values scatter largely. In the present research, the flow around a circular cylinder was chosen from the viewpoint of the experimental method and the mechanism of bubble occurrence because it has essetially the same characteristics as complex jet flows. The following points were made clear : a)the effects of air content b)the effects of methods of pressure reduction in water tunnel, c)the method of defining the inception point and/or desinent point of bubbles, d)measurement uncertaint … More y on cavitation test. The method of bubble occurrence test and the method of defining bubble occurrence point were established through these results.3. The flow around a circular cylinder changed qualitatively by the existence of bubbles under high air content, so that the characteristics of bubble occurrence changed greatly. Next, the experiment on bubble occurrence was conducted in low Reynolds number using thin wires. The results show that the mechanism of bubble occurrence depends on Weber number, different from high Reynolds number range and the appearance of bubbles is also different. The important factors on bubble design in complex jet flows were investigated through these results.4. The nozzle-test section was constructed after the above-mentioned results. The appearance and characteristics of bubble occurrence in jet flows were investigated using a laser doppler velocimeter, a high speed motion movie, a video-camera syncronyzed with a micro-flash, a measurement system for shock pressure and so on. Less