Diffusion of Bubbles in Two-Phase Flow : The 1st Report, On the Method for the Measurement of the Diffusivity of the Bubble

Abstract

Measuring the spread of tracer bubbles from a point source located at the center of an 80 mm. dia. pipe, we obtained the information of the diffusion of bubbles in a fully developed turbulent air-water two-phase flow. The features of the measuring technique in this apparatus are as follows: First, the local void fraction is measured with a fiber glass probe based on the principle of light refraction. Second, we used a sampling probe based on the principle of the hot-wire anemometer probe, by which we were able to discriminate bubbles between helium(tracer) and air. As a result, we conclude that the diffusivity of the bubble is smaller than the eddy diffusivity of momentum and it increases with an increasing value of void fraction.