Experimental analysis of local void fraction measurements for boiling hydrocarbons in complex geometry – Discussion

APRIN et al. (2007) should be congratulated for their significant contribution. They presented some challenging gas-liquid flow measurements with three different gases in a complex geometry using some interesting signal-processing. Herein the aim is to complement the discussion on local void fraction, especially in terms of the second statistical moment and signal correlation analyses. It is shown that there is a parabolic relationship between the second statistical moment of void fraction and the time-averaged void fraction, and it is valid for a broad range of gas-liquid flow situations. Some basic correlation analyses of the probe signal outputs may lead further information on the turbulent length and timescale of the gas-liquid flow. While the technique was validated in high-velocity free-surface flows, it is applicable to other gas-liquid flow situations