Statistical characterization of the interfacial behavior of the sub-regimes in gas-liquid stratified two-phase flow in a horizontal pipe

Abstract

The aim of the present study was to identify the interfacial behavior of the sub-regime of gas-liquid stratified two phase flow by using the pressure differential signal data. Here, the probability distribution function (PDF), power spectral density (PSD), kolmogorov entropy and discrete wavelet transform (DWT) were used to analyze the differential pressure signals. The indicators of each flow sub regime were analyzed on the basis of the quantitative values of the statistical curves, which were also validated by visual observation of the video images. The results indicated that there are six identified sub-regimes of stratified flow namely stratified smooth (S), two-dimensional (2-D) wave, three-dimensional (3-D) wave, roll wave (RW), entrained droplet + disturbance wave (ED + DW) and pseudo slug (PS). Next, the increase of liquid viscosity will shift the transition line from the RW to ED + DW to a lower both of JL and JG. The increase of the liquid viscosity provides a stabilizing effect to reduce the chaos of the pressure gradient fluctuation. For the RW and the ED + DW sub-regime, the increase of the liquid viscosity shifts the wavelet energy to a larger scale and lower frequency. For the PS sub-regime, the increase of liquid viscosity shifts the wavelet energy to a smaller scale with a higher frequency. For the RW sub-regime, the increase of JG will increase the wavelet energy at the small-scale and high-frequency decomposition levels.