New Closure Relations for the Interfacial and Wall Shear Stresses and Interfacial Curvature for Two-Phase Stratified Flows

摘要

Theory-based closure relations for the average wall and interfacial shear stresses in concurrent or countercurrent stratified flows with a smooth interface are introduced. The closure relations are formulated in terms of the single-phase based expressions, which are augmented by two-phase interaction factors, due to the flow of the two phases in the same channel. These closure relations were used as a platform for introducing necessary empirical corrections required in the stratified wavy flow regime. It is shown that the inclusion of the wave effect on the shape of the interface is essential for improving the two-fluid model predictions of the holdup and pressure drop in gas-liquid systems. Based on experimental data available from the literature, new empirical correlations for the wave effect on the interface curvature, on the interfacial shear and on the liquid wall shear were obtained. The predictions of the two-fluid model for the pressure gradient and holdup favorably compare with the exact solution for laminar stratified flows and with extensive data bank of gas-liquid stratified flows in the smooth and wavy regimes.