VISUALIZATION OF VAPOR BUBBLE GROWTH

The growth of a single microscopic water vapor bubble under low-pressure condition at the heated surface is investigated experimentally. Details about the shape development of the bubble and velocity of the interface are studied using an image-process ing scheme specifically developed for this purpose. The interface velocity is evaluated using an optical flow based PIV technique. The flow seeded with thermochromic liquid crystals is used to evaluate velocity and temperature fields surrounding the bubble. It is found that under the investigated conditions observed bubbles usually exhibit non-spherical shape. The bubble detachment precedes development of a neck-like structure. In many details it recalls images of large air bubbles moving through a very viscous fluid or the break-up of a liquid jet.