Despite the significance of rough-wall turbulent flows in many engineering applications (e.g. leading-edge erosion of wind turbine blades), we need up-to-date review papers on the topic. However, Kadivar, Tormey, and McGranaghan (2021) give us just that—with more than 500 references spanning 175 years of research, they analyse past and recent flow studies over rough surfaces to improve our general understanding and identify gaps for future research.

The paper first describes the classical division of the boundary layer into layers dominated by viscous or turbulent shear stresses and the classification of “smooth” and “rough” flow regimes using the concept of equivalent sand-grain roughness. It then outlines how roughness effects have historically been investigated experimentally and, more recently, numerically with high-resolution computational fluid dynamics (CFD).

While our understanding of turbulent flows over rough surfaces is still far from comprehensive, the paper concludes that continual research and modern CFD methods, like DNS, are the pathway to improve our fundamental understanding of rough-wall flows.

Kadivar, Mohammadreza, David Tormey, and Gerard McGranaghan. 2021. “A Review on Turbulent Flow over Rough Surfaces: Fundamentals and Theories.” International Journal of Thermofluids 10 (May): 100077. https://doi.org/10.1016/j.ijft.2021.100077.