The role of free-stream turbulence in the galloping instability of small-side-ratio rectangular cylinders

During a previous experimental campaign, a rectangular cylinder free to vibrate in the trans-verse degree of freedom showed a complicated behavior in turbulent flow. The present study aims at modelling the unsteady galloping behavior of the prism, incorporating the effect of homogeneous isotropic free-stream turbulence. Such an investigation represents a first attempt to explain some of the unclear features unveiled by the experiments. The nonlinear wake-oscillator model proposed between the 70s and 80s by Prof. Y. Tamura is adapted here to ac-count for the unsteadiness in the oncoming flow. The results clarify that the response of the cylinder in a relatively large-scale turbulent wind cannot simply be ascribed to linear or non-linear buffeting excitation. Rather, the unsteady contribution of vortex shedding seems to play a key role also in turbulent flow. Nevertheless, the oscillation amplitudes predicted by the model are significantly larger than in the experiments, so that a future refinement of the model is required.