FINITE ELEMENT ANALYSIS OF INCOMPRESSIBLE FLUID FLOWS IN A BACKWARD STEP DUCT USING COMSOL MULTIPHYSICS

Abstract

This study presents a numerical investigation of Newtonian fluid flow through a backward step duct using the Galerkin Least Square Finite Element Method (GLSFEM) within the COMSOL MultiPhysics environment. The research explores the impact of fluid inertia and geometric variations on flow characteristics, specifically focusing on aspect ratios of 1:6 and 1:12. By solving the incompressible stationary and non-stationary Navier-Stokes equations, the simulation characterizes vortex formation, recirculation flow rates, and reattachment lengths across a range of Reynolds numbers. Results indicate that increasing the Reynolds number and expansion ratio significantly enhances the intensity and length of primary and secondary eddies at the duct corners. Quantitative analysis is supported by newly developed empirical equations for recirculation flow rates, which demonstrate high correlation with existing literature. The findings provide critical insights for industrial applications involving flow separation and mixing, such as automotive silencers, chemical transport tanks, and turbine blade design.