抄録
This paper provides an experimental understanding of liquid film characteristics to examine flooding mechanisms in the countercurrent annular two-phase flow in a vertical tube. The experiments are performed in an air-water system with a large diameter tube, 50mm or 100mm in diameter. Time variations of liquid film thicknesses at four different elevations along the tube are measured, and their power spectra are used to examine interfacial wave characteristics. At the top region of the tube periodic wave with a frequency of about 45Hz is observed at a low gas flow rate condition. Increasing gas flow rate, the periodic wave disappears and the continuous spectra indicating a chaotic aspect is observed in the power spectrum profile. At the bottom of the tube the spectra indicate the continuous feature even at a low gas flow rate condition. As the gas flow rate increases, a power of the spectra increases due to large amplitude waves produced by interaction between the gas and liquid flows. The frequency of maximum power spectra shifts slightly to the low frequency region, but the profile does not change significantly before flooding. At the just before flooding, however, the profile become more flat in the high frequency region. The probability density of interfacial velocity increases in the large velocity region at just before flooding than at low gas flow rate condition. As the gas flow rate increases, the wave number of large amplitude tends to be small.
