This study investigates the behavior of Newtonian and nanofluid flows through a channel featuring a sudden expansion with an expansion ratio of 1:3, considering expansion angles of 30°, 45°, 60°, and 90°. Numerical simulations are conducted under laminar flow conditions using a two-dimensional incompressible flow model, incorporating nanofluids with nanoparticles (Al₂O₃, TiO₂, and CuO) dispersed in water at volume fractions of 0.5%, 0.75%, and 1%. The single-phase approach assumes thermal equilibrium between particles and fluid, reducing computational complexity. Key parameters, such as vortex length near channel walls, are examined in relation to Reynolds number, nanofluid type, nanoparticle concentration, and expansion angle. Results reveal that vortex length increases with Reynolds number, expansion angle, and nanoparticle volume fraction. Flow bifurcation and vortex asymmetry arise beyond critical Reynolds numbers, indicating flow instability. Validation against established data confirms the accuracy of the numerical model. These findings contribute to a better understanding of flow dynamics in sudden expansion geometries involving nanofluids, with implications for fluid transport and mixing applications.