A Numerical Approach to Marine Circulation Using Free Surface or Rigid-lid Modeling: Application in the Bay of Calvi

Abstract

When establishing a model of fluid flow in marine modeling, a key issue is the choice between a rigid-lid approach or a free surface level model. This is not a trivial issue as it plays an important role, not only in the choice of the numerical techniques, but also in the qualitative and quantitative aspects of the numerical results. Most software use either free surface or rigid-lid hypotheses, but comparing their results is difficult, since the numerical tools used are in general, extremely different. In this work, some numerical investigations comparing rigid-lid and free surface models are presented. A numerical method using Galerkin's method, but with a new basis, is applied to solve the rigid-lid equations in a realistic domain with varying bottom. A numerical method, similar to the one already used for free surface equations (the same truncating method and precision level) is applied, where the main differences between the simulation results depend only on the model employed. In addition, a comparative simulation between rigid-lid and free surface models to study marine circulation in the bay of Calvi (Corsica) is presented, and numerical results in the non-stratified case only (fluid with constant density) are described, as no further difficulties appear in the stratified case.