4. Modeling fluid-structure contact

As announced, fluid-structure contact modeling also proceeds on three hierarchical levels, from the simplest to the most sophisticated. Before going into the details of these three levels, it's important to note that, unlike solid modelling, fluid modelling and its influence on the eel's swimming behaviour cannot be as "satisfactorily" resolved. This is because eels, like all fish, make active use of unsteady phenomena, such as the vortices they release in their wake, to "optimize" their propulsion efficiency. The models and simulators associated with these problems of optimizing the propulsion of a deformable body immersed in a fluid are still an emerging topic in fluid mechanics. Here are the three levels of contact modeling and their function in the project:

• stationary models