The Investigation of Turbulent Buoyancy-Affected Flows for Cooling Applications

This paper details the Turbulent Flows that Affected with Buoyancy and the calculating of the heat transfer relevant to nuclear reactor in vertical pipe, the main topic when buoyancy effects play a significant role. Implementation of the analytical wall functions is used in when the aim is to reduce the computational cost, since conventional wall functions based on prescribed velocity and temperature profiles failed to predict heat transfer accurately in other than a simple shear at high Reynolds numbers. Thus, this work mainly concerns studying the effect of the buoyancy on heat transfer and turbulent flow applying the analytical wall function since it is based on the analytical solution of simplified Reynolds equations and using a new scaling function, which is used to modify the cell averaged dissipation rate. The approach gives results close to those obtained using AWF with scaling function introduced by Gerasimov. The benefit of using the Analytical wall function is that computational cost are more accurate than conventional wall functions. Many improvements added to the approach during its development have been employed in the present work. It has been successfully applied in natural, mixed and mixed convection flows for four different flow geometries.