Author(s): M. M. Piedra; H. Haynes; T. B. Hoey; A. Ervine

Linked Author(s): David Alan Ervine

Keywords: Shear velocity; Shear stress; Velocity profiles; Logarithmic law

Abstract: Bed shear velocity is commonly estimated using streamwise velocity profiles and the logarithmic law for the inner layer. However, despite a considerable number of empirical equations being reported in the literature, there is no unified expression of the log-law that is commonly applied to sediment transport studies. Most authors use essentially the same theoretical formulation, but the nomenclature and number of variables and parameters used in the equations are different. Not only does this cause confusion among practitioners and researchers, but it is difficult to compare shear stress values produced by different studies as the equations and assumptions that generate them are inconsistent. The objectives of this paper are therefore: i) to review log-law equations available in literature and compare their parameterisations; ii) to suggest a unified nomenclature for the variables and parameters of the log-law expression; and iii) to compare the main equation types using ADV measurements taken over a uniform gravel bed and a unimodal gravel bed in laboratory conditions. An additional near-uniform bed was used for validation of the method.

DOI:

Year: 2009