Turbulent Viscosity in Rough Oscillatory Flow

Abstract

In an earlier paper, a three‐layer model of an oscillatory rough turbulent layer was simplified to a two‐layer model. The model consisted of an overlap layer in which the turbulent viscosity varied linearly with height, and an outer layer in which the viscosity was constant. This paper improves the theory from the earlier paper: Turbulent viscosity is allowed to decrease linearly above the overlap layer until a certain height is reached, after which the viscosity is held constant. The viscosity everywhere is assumed time independent. The theory is compared with observations by other researchers. The agreement between theory and experiment is reasonably good. Also, a theoretical derivation of the wave friction factor is given, which for the larger excursion amplitudes agrees well with a previously established semi‐empirical friction factor formula.