Abstract
We experimentally studied the behavior of a single bubble in superpurified water. We developed the apparatus that can maintain the purity of water during the experiment. The apparatus is equipped with the measurement system for the resistance and TOC value of water so that we can quantitatively evaluate the purity of water. We investigated the critical Reynolds number over which the rising motion of bubble changed from rectangular to zigzag or spiral. We found out the critical Reynolds number was 660 for a bubble in superpurified water. We also compared the experimental results for terminal rise velocity and drag coefficient with the theoretical value for ellipsoidal bubble obtained in the limit of potential flow theory. For small bubbles, experimental values of the terminal velocity and drag coefficient were in good agreement with theoretical ones. For large bubbles, however, experimental values and theoretical ones had the relative deviation of about 8% in the terminal velocity and drag coefficient. This is because the bubble shape shows a deviation from fore-aft symmetry.
