Pressure recovery of two-phase flow across sudden expansions

An analytical formulation for the pressure recovery of two-phase flow across a sudden expansion was developed. The formulation takes into account the change in void fraction across the expansion, the pressure difference between the upstream flow and the downstream face of the expansion and the additional wall shear stress in the developing region downstream of the expansion. Experiments were performed using air–oil two-phase flow to evaluate the relative contribution of the different terms to the pressure recovery for three area ratios of 0.0625, 0.25 and 0.444. The current formulation, which takes into account all the relevant terms, was found to improve the prediction of the pressure recovery over existing models.