PREDICTION OF TURBULENT OSCILLATORY FLOW OVER ROUGH BEDS

A theory for the turbulent oscillatory boundary layer flow over a rough bed based on a two-equation turbulence model is presented. The resulting system of three coupled partial differential equations is solved by a finite difference method. A bench mark computation is included, but the results are given mainly through a comprehensive comparison with three independent sets of experimental data. The theory is shown to give excellent predictions for mean-flow quantities like ensemble-average velocities. Favorable predictions for turbulence quantities like turbulent kinetic energy and length-scale are obtained except in the close vicinity of the bed. In this area it appears that the traditional boundary conditions for the turbulence model variables have to be modified in order to be appropriate in the unsteady boundary layer.