Two-phase flow structure close to orifice contractions during horizontal intermittent flows

Two-phase horizontal intermittent flow through orifice contractions is experimentally investigated by means of a new impedance meter able to collect void fraction data simultaneously at different pipe locations. The investigation focuses on two-phase structure in the region downstream of orifice. Experiments were carried out on horizontal air–water flows in 40 mm inner diameter pipes. Six different orifice plates were considered, as combinations of two restriction ratios and three plate thicknesses. The results demonstrate that the orifices generally induce a marked increase in the downstream void fraction values, and that this is associated to a reduction in film thickness in the stratified regions.