PSEUDO-LAMINARIZATION OF MICRO-BUBBLE CONTAINING MILKY BUBBLY FLOW IN A PIPE

Micro bubble technology has become to attract people’s concerns due to its wide potential in practical applications to a variety of advanced and conventional science and technologies. However, our knowledge of micro bubbles containing bubbly two-phase flow is almost nothing. We developed a specially designed nozzle which generates high intensity micro air bubbles (mean diameter~ 40microns, number density more than 2×10/cc). Using this micro-bubble generator, we carried out, as a first step, a measurement of two-phase frictional pressure drop, cross-sectional average void fraction and liquid velocity profiles. The measurement of local void fraction is underway. The range of average void fraction was up to 0.6 % which is enough to realize milky bubbly flow. The most exciting result we found is that the two-phase flow becomes laminarized by injecting such ultra small bubbles into the water flow. For 0.3~0.5% void fraction, laminar-turbulent transition occurred at Re=10,000~20,000. The cross sectional averaged void fraction does not follow a homogeneous flow model, and radial liquid velocity profile was a little bit flattened. The mechanism of flow laminarization and flow structures are now being pursued.