A comprehensive examination of turbulent Reynolds numbers at regular, converging, and diverging outlets may be referred to as necessary knowledge for optimizing fluid dynamics in engineering applications as it enhances understanding of flow behavior and improves design efficiency. This report presents the variation of turbulent Reynolds number, turbulent kinetic energy, and effective viscosity of three kinds of fluids (i.e. air, water, and kerosene) in y-shaped cylindrical copper ducts with regular, converging, and diverging outlets. The SpaceClaim was used to design the duct such that the diameter of the two inlets is 40 mm. The diameters of the diverged and converged outlets are 70 mm and 10 mm respectively. The SST(k-ω) viscous model in Ansys Fluent 2023R2 was adopted as a better approach for handling adverse pressure gradients and capturing boundary layer behavior. The simulation and meticulous meshing of the ducts were achieved using waterlight workflow. Reliable and valid results were obtained after adopting suitable boundary conditions, grid independence, and solver settings. Worth concluding that when the entry velocities of cold and hot water are equal and small in magnitude, higher turbulent Reynolds numbers (〖Re〗_y) occur at the diverged outlet due to enhanced mixing and vorticity. The substantial difference in velocities of hot and cold air (2 m/s for hot air and 12 m/s for cold air) leads to strong mixing and a resultant airflow that is significantly influenced by the properties of the cold air. Higher inlet velocities, whether from hot or cold fluids (i.e. air, water, and kerosene), increase the velocity magnitudes at all outlets, but the effects vary depending on which inlet velocity is increased. Fluid thermal conductivity plays a crucial role in determining static temperature at outlets, with higher conductivity fluids (air and water) showing higher temperatures than lower conductivity fluids (kerosene).