Créé le : 27/09/2010 - Mis à jour le : 15/11/2012
An experimental study was performed in order to describe the single- and two-phase (air-water) horizontal flow in presence of a pipe expansion. Two types of singularities were investigated; sudden and progressive enlargement. In the lateral case, the opening angles of the divergence geometry were 5, 8 and 15 degrees. The surface areas examined were σ=0.43 and σ=0.65. Bubbly flow was the dominant flow regime that was investigated for volumetric qualities up to 30 %. The pressure recovery for the case of both single and two-phase was plotted versus axial position and it was shown that the smallest the angle, the largest the recovery pressure for the same flow conditions. This is due to the pressure drop that is caused by the singularity which is higher in the case of a sharper enlargement. The results were compared to literature models and in order to predict the singular two-phase pressure change in progressive enlargement, a coefficient of adaptation for Jannsen’s (1966) model is proposed. Flow visualization has shown that the change of flow regime is associated either to the two-phase condition, to the geometrical characteristics of the singularity or to a combination of them depending on the mass velocities of the two-phases.