Enhancing the two-layer k-epsilon turbulence model through rough wall modification

Surface roughness significantly influences turbulence structures, affecting skin friction and velocity profiles. Precisely modeling the roughness effects is essential for reliable numerical simulation results in various engineering applications. This paper introduces enhancements to the two-layer k-epsilon (k−ε) turbulence model, incorporating surface roughness effects by adjusting variables in prescribed length scales and turbulent boundary conditions and ensuring the model switches between different roughness regimes. The accuracy of the enhanced model was validated using the Grigson–Colebrook type roughness function and experimental data from flat plate flows, as well as more complex geometries such as sand dune flow and ramp flow. The modified model demonstrated strong agreement with experimental data, accurately predicting the effects of roughness across diverse flow conditions, particularly in terms of velocity profiles. The proposed roughness modifications substantially improve the model's capability to simulate turbulent flows over rough surfaces, providing a valuable tool for predicting flow behavior in engineering applications involving rough surfaces.