Local impact of roughness topography on heat transfer in turbulent flow over rough surfaces

Additive manufacturing (AM), particularly Laser Powder Bed Fusion, produces surfaces with unique, randomly distributed spherical roughness that significantly influences heat transfer and pressure loss. This study models AM roughness using a statistical distribution of spheres and performs high-fidelity simulations at a bulk Reynolds number of 12,000 to evaluate heat transfer on a rough pipe. Statistical measures were deployed to highlight a clear correlation between roughness height and heat transfer. By analyzing probability density functions of roughness height and the normalized local Nusselt number, along with their conditional and joint distributions, the study demonstrates that local heat transfer enhancement is strongly dependent on roughness height and it’s distribution. Specifically, elevated roughness elements correlate with increased heat transfer due to enhanced turbulence and flow disruption, whereas smaller or sheltered roughness elements contribute minimally.