Experimental and numerical characterization of the dynamic behavior of an undulating membrane tidal energy converter

The thesis presented in this document deals with the characterisation of the behaviour of an undulating membrane tidal energy converter. This kind of device uses the flutter instabilities occurring between a semi-rigid pre-strained membrane and a fluid flow in order to convert the sea currents energy. Above a certain critical flow speed, the structure undulates, thus activating the linear converters fixed on it. In order to study this system, an experimental model is developed and tested in a flume tank. The power conversion system is simulated by hydraulic dampers. The membrane's dynamics is analysed in many configurations through trajectory and force measurements, and leads to a parametric study. More realistic flow conditions are also studied, such as the impact of current direction influence and the influence of surface waves on the behaviour of the system. Wake characterisation is carried out with two-dimensional PIV measurements. Scale effects and confinement are also studied through a comparison with a bigger scale prototype tested in tank and at sea. In addition to the experimental study, an analytical model and a numerical model are developed and compared with experiments. The linear analytical model is based on Euler-Bernoulli's beam theory and on Lighthill's slender body theory. It is solved in the frequency domain and gives good undulation frequency and critical speed results. The numerical model uses strong interactions between a fluid code using the vortex method and a structure code based on co-rotational finite elements. This model is validated on an experimental case. (author)