Modeling of pressure drop in two-phase flow within expansion geometries

An experimental study is performed in order to describe the single‐ and two‐phase (air‐water) horizontal flow in presence of a pipe expansion. Two types of singularities are investigated; sudden and progressive enlargement. In the lateral case, the opening angles of the divergence geometry are 5, 8 and 15 degrees. The surface area ratios tested are σ = 0.43 and σ = 0.65. Bubbly flow is the dominant flow regime that is investigated for volumetric quality up to 30%. The pressure recovery for the case of both single and two‐phase was examined versus axial position. It is found that the smallest is the enlargement angle, the largest the recovery pressure for the same flow conditions: the pressure drop caused by the singularity is higher in the case of a sharper enlargement. The comparison of the experimental results to published models leads to proposed corrective coefficient for Jannsen’s (1966) correlation. Flow visualization is also performed; the flow patterns downstream the different singularities are identified in each configuration and plotted in Baker’s (1954) map for horizontal flow.