Investigation of Newtonian Fluid Flow through a Two- dimensional Sudden Expansion and Sudden Contraction Flow Passage

–The importance of flow through sudden change in flow passages lies in the numerous industrial applications such as, polymer processing, injection molding, biomedical instruments, extrusion, thermoforming etc. In this work, fluid flow through an axi-symmetric sudden contraction flow passages has been carried out using commercial CFD tools. Flow in the inverse direction, which represents flow through a sudden expansion, has also been simulated for the same conditions. A comparison has been established between the two flows occurring in the opposite direction. A twodimensional computational domain has been chosen for the analysis considering steady, laminar flow and Newtonian fluid. The effects of flow rates are investigated with constant diameter ratios to understand the flow characteristics for sudden expansion and sudden contraction geometry. The size of the recirculation zone, flow reattachment length, redevelopment of flow, recirculating flow strength depends on several parameters, primarily on flow rate i.e. Reynolds number, expansion/contraction ratio and flow direction. Flow tends to become unstable at lower Reynolds number for high expansion ratio. Keywords––Sudden Contraction, Sudden expansion, Recirculation, Flow Separation, Flow Reattachment.