Simple models for turbulent wave-current bottom boundary layer flow : theoretical formulations and applications

Abstract

This study presents the theoretical formulations and applications of simple models for turbulent wave-current bottom boundary layer flow. Eddy viscosity formulations are presented for each model in order to analytically solve the governing equations for the bottom boundary layer. Approximations and procedures for obtaining practical solutions of the current velocity profile are presented for the two-layer Madsen-Salles (1998) and three-layer Barreto-Acobe (2001) flow models. Bottom roughness and ripple geometry models are developed for each model using fixed bed laboratory data and movable bed laboratory and field data. Wave attenuation measurements and current profile data are used in order to investigate the bottom roughness length scale for the cases of pure waves, waves in the presence of a current, and currents in the presence of waves. Wave and sediment characteristics are used to formulate a model for wave-generated ripples based on available laboratory and field data. The two-layer Madsen-Salles (1998) and three-layer Barreto-Acobe (2001) flow models are applied in conjunction with the ripple geometry and roughness models for the cases of known and unknown ripple geometry, and an assessment of expected accuracy of application of the models is presented.