Air flow through an axisymmetric sudden expansion of confined co-axial circular duct: Numerical study

Fluid flow through an axisymmetric abrupt amplification geometry is widely employed in several engineering applications. In the present study, the examination of turbulent air flow through a sudden pipe expansion has been carried out using the CFD code ANSYS-FLUENT. The heat transfer in confined co-axial air jets in an axisymmetric sudden pipe expansion has been analysed. Three turbulence models have been employed to compare flow predictions of each model. The results show that the predictions of Reynolds Stress Model are more reasonable and realistic, particularly in the recirculation zones. Another important variable studied is the inlet flow velocity (i.e. Reynolds number). Reynolds number increase leads to enhance each of pressure drop, turbulent viscosity, and return-flow velocity and flow shear stress on the surface of the wall. In terms of heat transfer, the effects of the thickness of central jet wall on the heat transfer and turbulent flow in the flow domain have been investigated. Furthermore, a variation of inlet velocity of the annular jet has been considered in the investigations of the heat transfer and flow turbulence. Most predicted flow variables are closely confirmed by those reported in the literature as well as the numerical calculations.