About the wave-current interactions: a framework for the use of the two-way mode

An important goal for the future is to simulate coastal circulation with the greatest accuracy and lowest computational cost, in particular to study marine submersion, the dispersion of pollutants and sediment transport. For all of these fields of application, wave-current interactions play an important role. We propose to define a framework for the use of the three-dimensional numerical wave-current model because of its combination with sediment transport and biological models, which increase computational time. The importance of the feedback of the flow on the waves is particularly investigated in the context of idealized (Yu et Slinn, 2003) and realistic (Bruneau et al, 2009) barred beaches. The fully coupled model MARS3D-WAVEWATCH III (Bennis et al, 2011) based on the vortex force formalism is used. The differences between the one-way and two-way modes with horizontal resolution are highlighted. First, the results obtained by Weir et al (2011), for the barotropic mode and for finer resolution, are found, which validates our modelization. Next, we show that (a) from coarser to finer meshes, the differences between the two modes are greatly increased, in particular by a factor of two on the magnitude of the rip current; (b) the vertical structure of the rip current and the momentum balance is also affected by the feedback, with a decrease in the vertical shear of the rip current when the feedback is activated. We conclude that the one-way mode is sufficient with the coarse mesh and a classification defining the framework for the use of the numerical wave-current model is established with the computing time for each situation. In the future, we will work on taking into account the feedback effects in the one-way mode using inverse methods in order to further decrease computational time