Modeling of turbulent flow over a channel with a rough surface using a turbulence model k-ε

Surface roughness significantly affects aerodynamic and heat transfer processes by modifying the boundary layer structure and increasing turbulence intensity. This study presents a numerical investigation of turbulent flow in a channel with smooth and rough walls using the k - ε turbulence model implemented in Comsol Multiphysics 6.2. Calculations were performed for different equivalent sand-grain roughness heights corresponding to smooth, transitional, and fully rough regimes. The velocity profile, friction coefficient, and Stanton number were analyzed and compared with experimental data. The results show that the standard k - ε model provides satisfactory agreement for friction and heat transfer characteristics, while discrepancies appear near the wall and in transitional regions.