Sensing and modeling of a hydroelastic lifting body

Fluid structure interaction (FSI) describes the coupling of fluid dynamic forces on a structure and the corresponding motions of that structure. FSI in dense viscous fluids, known as hydroelasticity, is filled with rich physics that affect a wide range of engineering disciplines. Robust adaptive control of these hydroelastic systems offers a path towards more efficient marine propulsors [1], versatile bio-inspired robotics [2] and effective energy harvesting solutions [3]. In order to provide accurate models and robust controllers, in depth understanding of underlying physics is indispensable. Numerical predictions look to couple computational fluid dynamics and finite element models to capture complex hydroelastic interactions [4]. These models require insight into the energy transport, transfer, storage, and dissipation mechanisms - physical insights that are currently lacking. Experimental measurements, which seek to characterize the effects of fluid flows on the dynamics of a structure, are sparse and exhibit high uncertainties. This is in part due to the non-linear nature of fluid forces, and the lack of established experimental methods. Additionally, accurate measurements are often difficult to obtain because of undesirable flow conditions. In order to fully realize the benefits of hydroelasticity, sensing techniques must be improved, accurate system modeling must be developed, and better interpretation of modeling changes must be explored. This thesis shall address these three areas of need. An accurate kinematic shape sensor (KSS) is developed using a robust kinematic model paired with a shape sensing spar which is instrumented with strategically placed strain gauges. The accurate deflection measurements are shown to be capable of accurate parameter estimation. The KSS is shown to be an excellent source of data for the accurate output-only estimation of system parameters such as natural frequencies, damping ratios, and mode shapes. Moreover, a new co-analysis method is proposed to better interpret interactions between flow patterns and the structural dynamics.