Impact of non-uniform inlet gas flow distribution on two-phase flow characteristics in a rectangular channel

Two-phase flow in rectangular channels is prevalent in numerous industrial applications, requiring precise predictive models to guarantee operational safety and efficiency. To achieve a more detailed analysis of two-phase flow in rectangular channels, the two-group (2G) approach has been adopted, categorizing bubbles into two distinct groups. In this approach, group one (G1) bubbles correspond to distorted spherical bubbles, while group two (G2) bubbles comprise churn-turbulent, slug, and cap bubbles. The 2G two-fluid model, combined with the interfacial area transport equation, has been proposed to enable dynamic predictions of void fraction and heat transfer characteristics in two-phase systems. The 2G drift-flux model has also been proposed as a critical closure relation for the one-dimensional 2G two-fluid model. The 2G drift-flux correlation in rectangular channels, which closes the 2G drift-flux model, has been developed based on experimental data obtained in a rectangular channel under uniform inlet boundary conditions characterized by uniform distributions of gas flow rate. The present study investigated the impact of non-uniform inlet boundary conditions, characterized by non-uniform distributions of gas flow rate, on void fraction and the 2G drift-flux correlation in a rectangular channel. Significant deviations exceeding 30% were observed in predictions of G1 and G2 void fractions under the channel center peak gas flow (CPG) and single sidewall peak gas flow (SPG) conditions. Therefore, G1 and G2 distribution parameters in the 2G drift-flux correlation were modified. The modified 2G drift-flux correlations accurately predicted the G1 and G2 void fractions under CPG and SPG conditions. © 2026 Author(s).