This document summarizes a study investigating fluid flow through two-dimensional sudden expansions and contractions. The study uses computational fluid dynamics (CFD) to simulate fluid flow through axisymmetric geometries with varying diameter ratios and Reynolds numbers. Results are presented on flow characteristics like recirculation zones, reattachment lengths, and vortex strengths. Validation is provided by comparing simulations to experimental particle image velocimetry data. Key findings include higher instability at lower Reynolds numbers for large expansion ratios and variations in recirculation zone size and redeveloped flow with changes in Reynolds number and diameter ratio.