Study of unsteady gas-liquid two-phase flow induced force fluctuation (Part 1: Evaluation and modeling of two-phase flow induced force fluctuation)

Abstract

Fluctuating force induced by upward gas-liquid two-phase flow on 90 degree pipe bend was investigated. From the previously developed database comprised of dynamic force signals and two-phase flow parameters such as volumetric fluxes, area averaged void fraction and pressure fluctuations, the study was conducted to develop a model which is capable of predicting the force fluctuation magnitudes. The model was fundamentally developed from the local instantaneous two-fluid model applied on the control volume of 90 degree elbow. The force fluctuation of two-phase flow is caused by momentum and pressure fluctuations. For slug flow regime, however, it was found that impact force caused by the collision of liquid slug against the structure boundary produces “water-hammer” like impact. In order to avoid discontinuity due to flow regime transition, interfacial area concentration correlation was utilized using two-group approach. The newly developed model is capable of predicting two-phase flow induced force fluctuation and dominant frequency range with satisfactory accuracy.