Anne-Claire Bennis

Numerical Wave Modeling in Conditions with Strong Currents: Dissipation, Refraction, and Relative Wind

AbstractCurrents effects on waves have led to many developments in numerical wave modeling over the past two decades, from numerical choices to parameterizations. The performance of numerical models in conditions with strong currents is reviewed here, and observed strong effects of opposed currents and modulations of wave heights by tidal currents in several typical situations are interpreted. For current variations on small scales, the rapid steepening of the waves enhances wave breaking. Using different parameterizations with a dissipation rate proportional to some measure of the wave steepness to the fourth power, the results are very different, none being fully satisfactory, which points to the need for more measurements and further refinements of parameterizations. For larger-scale current variations, the observed modifications of the sea state are mostly explained by refraction of waves over currents and relative wind effects, that is, the wind speed relevant for wave generation is the speed in the ...

Numerical Wave Modeling in Conditions with Strong Currents: Dissipation, Refraction, and Relative Wind. J

AbstractCurrents effects on waves have led to many developments in numerical wave modeling over the past two decades, from numerical choices to parameterizations. The performance of numerical models in conditions with strong currents is reviewed here, and observed strong effects of opposed currents and modulations of wave heights by tidal currents in several typical situations are interpreted. For current variations on small scales, the rapid steepening of the waves enhances wave breaking. Using different parameterizations with a dissipation rate proportional to some measure of the wave steepness to the fourth power, the results are very different, none being fully satisfactory, which points to the need for more measurements and further refinements of parameterizations. For larger-scale current variations, the observed modifications of the sea state are mostly explained by refraction of waves over currents and relative wind effects, that is, the wind speed relevant for wave generation is the speed in the ...

Comments on ``The Depth-Dependent Current and Wave Interaction Equations: A Revision''

AbstractEquations for the wave-averaged three-dimensional momentum equations have been published in this journal. It appears that these equations are not consistent with the known depth-integrated momentum balance, especially over a sloping bottom. These equations should thus be considered with caution, because they can produce erroneous flows, particularly outside of the surf zone. It is suggested that the inconsistency in the equations may arise from the different averaging operators applied to the different terms of the momentum equation. It is concluded that other forms of the momentum equations, expressed in terms of the quasi-Eulerian velocity, are better suited for three-dimensional modeling of wave–current interactions.

Regional numerical modelling of offshore monopile wind turbine impacts on hydrodynamics and sediment transport

The purpose of this work is to find a parameterization which is able to represent properly the modifications caused by offshore wind turbines foundations on the hydrodynamics and sediment transport at regional scales. As a case study, the regional hydrosedimentary model MARS3D is applied on an area including the future offshore wind farm of Courseulles-sur-Mer (Normandy, France). Turbines are represented in the model using two approaches. The first method takes into account monopiles directly in the mesh as dry cells and the second one uses a sub-grid parameterization method by adding drag force term in momentum equations and source terms in k-epsilon turbulence model equations. Comparisons between the results obtained by the different approaches are carried out. As expected, both show impacts on the circulation, with formation of a wake downstream, flow deceleration in front of the pile, and flow acceleration at the side edges. Near-bed erosion occurs in locations where current speeds increase due to the monopile presence, leading to an increase of suspended sediment concentration.