Statistical Characteristics of Differential Pressure Fluctuations and Flow Patterns of Gas-Liquid Two-Phase Flow in an Inclined Pipe

Differential pressure fluctuations are used to characterize various flow patterns in inclined two-phase flows as well as in vertical and horizontal flows. They are measured at the short observation scale equal to the pipe diameter and the long observation scale equal to ten times the diameter, to detect local and instantaneous flow changes corresponding to variations of the gas phase at the measuring interval or location. The experimental results show that nitrogen gas or air-water mixture flow in an inclined pipe of 20 mm i.d. exhibits peculiar features of statistical properties (probability density function and power spectral density function), and the flow patterns can be classified by the statistical characteristics of differential pressure fluctuations. Thus, it appears that an objective judgement of flow pattern can be made using statistical parameters such as standard deviation and coefficients of skewness and excess.