Fluid–Structure Interaction of a thin cylindrical shell filled with a non-Newtonian fluid

This paper presents the results of an extensive experimental campaign on the dynamic interactions between an elastic structure and a non-Newtonian fluid. The structure consists of a thin circular cylindrical shell, with the bottom end clamped to a shaking table, and the top end carrying a heavy mass. The fluid is a mixture of water and cornstarch, also known as oobleck. The system dynamics has been analyzed in the presence of different fluid levels (i.e., empty, partially, and full-filled). The experimental modal analysis has been carried out to identify the modal properties of the system. High energy tests have been performed by means of a seismic excitation consisting in a stepped sine sweep, spanning the forcing frequency within the neighborhoods where strong resonance phenomena take place. Different excitation amplitudes have been considered in order to induce phase transitions in the fluid, and the onset of complex dynamics has been detected using Fourier spectra and bifurcation diagrams of the Poincaré maps: when the fluid–solid​ transition occurs, the entangled non-Newtonian fluid rheology results in a complex dynamic scenario where period-doubling cascades, quasiperiodic and chaotic responses can be observed.