Experimental characterization of gas–liquid intermittent subregimes by phase density function measurements

Abstract

The transition between plug and slug flow patterns in a horizontal gas–liquid flow is studied experimentally by means of statistical analysis of the gas density function time series. Two parameters are introduced in order to characterize the transition: the ratio of the probability density function maxima and the power spectrum mean frequency. For a given liquid superficial velocity, the partial derivative of these parameters displays abrupt changes in value with respect to the gas superficial velocity where the flow pattern transition occurs. The experiments were carried out on an air–water flow in a horizontal pipe of i.d. 0.08 m; the water mass flow rates were 3, 4.5, 7, and 10 kg/s, while the gas fraction of volume flow ranged from 0.2 to 0.8; single-fiber optical probes measured the gas density function time series at a sampling rate of 2 kHz. The results agree with the Mandhane map and provide a basis for a theoretical description of the transition.