Influence of Surface Roughness Topography on Heat Transfer in Turbulent Flows

This study models Additive Manufacturing (AM) roughness using a statistical distribution of spheres and performs high-fidelity simulations at a bulk Reynolds number of 12,000 and a large range of Prandtl numbers to evaluate heat transfer on a rough pipe. Statistical measures were deployed to highlight a clear correlation between roughness features and heat transfer. To directly connect surface topography with local heat transfer, the roughness height map was classified into quantile-based roughness zones: canyons, lower slopes, upper slopes, and tips. Probability density functions of the normalized Nusselt number in these zones reveal a clear stratification of convective performance: canyon regions exhibit the lowest heat transfer due to shielding and limited turbulent renewal, while tip regions consistently achieve the highest values through direct exposure to turbulent eddies and boundary-layer disruption. A complementary sheltering analysis based solely on surface visibility to the incoming flow distinguishes weakly ventilated regions with suppressed heat transfer from exposed windward faces that host intense thermal events. Probability density functions of the local Nusselt number based on sheltering analysis reveal pronounced spatial variability linked to surface geometry. ... mehrThese findings highlight the central role of roughness elevation and spatial exposure in governing turbulent heat transfer and provide new insights into the thermal-hydrodynamic behavior of AM-fabricated channels.