Integration of piezoelectric transducers in hydrofoils made of composite materials
Résumé
Boat appendices, known as hydrofoils, can be subjected to significant dynamic stress during navigation at high Reynolds (Re > 10^5). The turbulent nature of the flow as well as vortex shedding at the trailing edge generate structural vibrations which couples with the resonant modes of the foil. These phenomena, turbulence induced vibration (TIV) and vortex induced vibrations (VIV), leads to undesirable structural fatigue and radiated noise. This study describes the integration of piezoelectric transducers in hydrofoils manufactured in composite material made of carbon fiber and epoxy resin. Macro Fiber Composite (MFC) patches are used to sense and possibly control bending and torsional vibrations induced by the flow. Two hydrofoils with the same external dimensions but obtained with dierent manufacturing processes are considered. The external shape corresponds to a NACA 006 truncated at 80% with a 100 mm chord and 191 mm wingspan. The internal geometries and the arrangement of the composite plies are described for both manufactured hydrofoils. In addition, their respective finite element (FE) models are built according to the manufacturing specifications. Particular attention is paid to the modeling of the piezoelectric transducers and the associated electromechanical coupling. Indeed, the FE models have been created to perform modal analyses of the hydrofoils in air and in water and then optimize coupling factors between the transducer and the structures. To do so, two types of configurations are tested: one with the MFC transducer disabled (short-circuit) and a second with the MFC transducer activated (open-circuit) in order to compute the natural frequencies of the structure in both configurations. The coupling factor, directly related to the dierence between these two natural frequencies, then depends on the location of the MFC on the foil span. The next step in this study is to experimentally validate the coupling factors computed by the FE model. This work is part of the HYDRAVIB project, which aims to develop a hydrofoil vibration mitigation systems based on the integration of piezoelectric transducers.

