Numerical Simulation and Flow Pattern Evolution of Gas-Liquid Two-Phase Flow Passing Through a 90° Pipe Bend Based on CFD

In order to investigate the evolution characteristics of gas-liquid two-phase flow passing through a 90° pipe bend, the volume of fluid (VOF) multiphase flow model and the Realizable k-ε turbulence model are used to conduct numerical simulations. The evolution of velocity, pressure distribution, gas void fraction, and flow pattern passing through a 90° pipe bend is studied in detail. The results show that different gas-liquid two-phase flow patterns will produce different degrees of secondary flow phenomenon after passing through the 90° pipe bend, and the tangential velocity presents a bimodal distribution, which eventually dissipates into a unimodal distribution in the horizontal pipe. The pressure on the outer wall of the pipe bend increases as the inlet velocity increases. The change of gas void fraction is related to the transformation of the flow pattern, the bubbly flow evolves into a slender slug flow in the horizontal pipe after passing through the 90° pipe bend, and the gas void fraction will decrease. The slug flow, the churn flow, and the annular flow evolve into the stratified-wave flow in the horizontal pipe after passing through the pipe bend, and the variation of the gas void fraction is relatively low. The research results can provide certain theoretical support for the design and development of gas-liquid two-phase flow conveying elbows and the prediction of induced stress.