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A three-dimensional numerical simulation of time-averaged wave-induced currents was performed, its results were compared with the results of a depth-integrated Boussinesq equation model And the differences were discussed in terms of wave height, instantaneous and mean free surface elevations, mean and time-averaged velocity fields, and turbulence parameters. For the three-dimensional simulation, an internal wave generation and a wave-absorbing sponge layer scheme, which can eliminate the influence of waves reflected from the wave source and wall boundaries toward the domain, were applied to the RANS equation model in a CFD code named FLUENT and the VOF model was utilized for the water surface In this study, two experiments involving wave-induced flows were simulated. First, to examine the wave-induced flows computed by the present model, we performed an existing two-dimensional experiment in which time-averaged mean motions induced by wave breaking were measured on a constant slope. Second, the breaking monochromatic wave case of Vincent and Briggs' experiments [Vincent and Briggs, 1989] was simulated in three dimensions using the present model. The experimental case presented a three-dimensional phenomenon in which a wave-induced jet-like current was generated and influenced the wave transformation over an elliptical submerged shoal. The computations agreed with the measurements and showed vertical distributions of the wave-induced currents over the shoal.

This study aims to develop a new numerical model for predictions of the time-varying shear current field under breaking and broken waves. The present model differs from the other similar existing models in that the model explicitly determines the bottom shear stress so that it satisfies both force balance and mass-conservation equations while most of the other existing models leave the bottom shear stress as one of the calibration parameters to be fitted. The present model consists of two sub-models, a wave model and a flow model. The wave model is based on modified Boussinesq equations with evolution and dissipation of surface rollers. The flow model is based on Reynolds' equations with turbulence closure models and computes vertical profiles of wave-induced shear current field. The numerical model is applied to various existing and newly performed experimental cases which cover various breaker types and bed profiles with different bed roughness. The present model showed overall good predictive skills of various surf zone hydrodynamics such as wave heights, mean water levels and undertow profiles. It should also be highlighted that the model has only a few calibration parameters and the predictive skill of the model is relatively less sensitive to these parameters.

Wave breaking over a submerged step with a steep front slope and a wide horizontal platform is studied by smoothed particle hydrodynamic (SPH) method. By adding a momentum source term and a velocity attenuation term into the governing equation, a nonreflective wave maker system is introduced in the numerical model. A suitable circuit channel is specifically designed for the present SPH model to avoid the nonphysical rise of the mean water level on the horizontal platform of the submerged step. The predicted free surface elevations and the spatial distributions of wave height and wave setup over the submerged step are validated using the corresponding experimental data. In addition, the vertical distributions of wave-induced current over the submerged step are also investigated at both low and high tides.

A new approach for prediction of wave-induced current over submerged breakwaters/reefs based on artificial neural networks (ANNs) is proposed. An ANN was designed and trained using artificial current data generated by analytical current model of Gourlay and Colleter (2005). Calculated discharge using the proposed model was compared with the measured experimental data collected by Tajziehchi and Cox (2006). Comparison of calculated and measured discharge over submerged breakwater reveals the accuracy of the proposed model and its capability in predicting discharge over submerged breakwaters/reefs.