Translational Slug Velocity Measurement Based on Fiber Optical Reflectometer

In horizontal gas-liquid slug flow, the translational velocity of the liquid slug and its axial velocity profile are important in guiding pipeline design and studying the formation and development mechanism of the liquid slug. This paper proposes a method for measuring the translational velocity in horizontal gas-liquid slug flow with a single optical fiber probe (OFP) based on fiber optic reflectometer technique (FOR). The wavelet synchronosqueeze transform (WSST) method is used to extract the frequency of the oscillation signal and to calculate the local velocity. Experiments under 15 velocity conditions are carried out in horizontal DN50 pipeline. The maximum velocity inside the liquid slug generally appears in the slug head area. As the distance between the probe tip and the front interface of the slug increases, the local velocity decreases and eventually stabilizes. The maximum velocity at the slug head area is selected as translational velocity of the slug. Compared with Bendiksen's empirical formula, the mean absolute percentage error (MAPE) is 5.44%. Under most velocity conditions, the relative error does not exceed 10%.