Explicit modelling of bottom friction in combined wave-current flow

Abstract

A direct, explicit solution technique is developed to estimate the time-mean bed shear stress and its frictional dissipation rate in combined wave-current flow. The present paper is the final part of the series papers concerned with the refinements of Bijker's modelling approach. In the early paper it was shown that Bijker's approach is widely applicable if consideration is given for the current velocity reduction as well as the near-bed velocity profile of wave motion. In the last paper the velocity reduction factor was shown to be represented by explicit expression so that numerical efficiency can be significantly improved. In the present paper the explicit expressions of various time-integrals and reduction factor are further modified by considering various flow conditions in order to improve the numerical accuracy in any flow conditions. The refined model is again tested against several sets of laboratory data including those published in recent years, and discussion is made on the computational results produced by various mathematical models.