Local scour around structures and the phenomenology of turbulence

The scaling of the scour depth of equilibrium at the base of a solid cylinder immersed within an erodible granular bed and impinged by a turbulent shear flow is investigated here, for the first time, by means of the phenomenological theory of turbulence. The proposed theory allows the derivation of a predictive formula that (i) includes all the relevant non-dimensional parameters controlling the process, and (ii) contrary to commonly employed empirical formulae, is free from scale issues. Theoretical predictions agree very well with experimental data, shed light on unresolved issues on the physics of the problem, and clarify the effects of various dimensionless parameters controlling the scouring process. © 2015 Cambridge University Press.