Modeling the influence of surface roughness on boundary layer transition

: This paper provides a summary of both history and current state-of-art in modeling of the surface roughness influence on boundary layer transition from laminar to turbulent regime. Discussed techniques are restricted to RANS models as these are nowadays still in major use in complex engineering applications. Present modeling techniques for surface roughness are critically reviewed. Finally, challenges connected with modeling of surface roughness influence are highlighted and potential ways for future work in this area are discussed.