A series of numerical simulations for inelastic and elastic non-Newtonian fluids through a two-dimensional planar sudden expansion is conducted using an in-house finite volume solver1.The geometries investigated are composed by three horizontal inlets of equal widths where the effect of their spacing is investigated. The obtained flow responses are further compared with the equivalent of a single-inlet configuration. Initially, flows of inelastic non-Newtonian fluids described by the power-law model are investigated for the considered multi-inlet configurations, demonstrating the importance of the spacing ratio between inlets and its influence on the resulting flow2. It was found that the spacing ratio between the inlets controls the formation of internal vortices, and leads to vortex interactions which affect the critical conditions causing the flow to become asymmetric and later time dependent. The study is then expanded to consider viscoelastic fluids of constant viscosity described by the upper-convected Maxwell (UCM)model. Creeping flow conditions (i.e Reynolds number (Re) tending to zero) are considered first, to investigate the effects of elasticity in the absence of inertia, where vortex-stabilising effects due to elasticity have been observed. This is in agreement with the observations of other studies employing single-inlet planar sudden expansion configurations3 4. For these conditions, intermediate vortices at the sections between the inlets are not observed, however interesting interactions are reported for varying Weissenberg numbers (Wi). Finally, to account for inertial effects and investigate the influence of vortex interactions, numerical simulations are performed at constant elasticity number (El = Wi/Re), which is representative of realistic experimental conditions
