Simulation of two-phase flow through ducts with discontinuous cross-section

The development of an AUSM+-up based scheme for simulating transient single or two-phase flows through ducts with discontinuous or abrupt changes in area is presented. The non-conservative terms in the governing equations arising from the variation in the duct area are discretised to maintain exactly states at rest. An additional scaling of the pressure based dissipation is added to ensure numerical stability across the area change. The extensive application of the scheme to ideal gas and two-phase CO2 based on the Homogeneous Equilibrium Model (HEM) for both shock tube and other transient flow problems indicate the scheme's capability to resolve such problems accurately and robustly.