A cantilevered flexible cylinder in cross-flow

Biological fluid-structure interactions of high aspect ratio bluff bodies are commonplace: flow around tall plants; flow through arrays of sensory vibrissae, antennae, and hairs. In this study, we seek insight to this class of problems by generalizing the flow configuration to uniform flow past a flexible cantilevered cylinder. Experiments were conducted for $Re_{D}$ = 100-500. Cylinders deflected with the flow and demonstrated multimodal oscillations in both the streamwise and transverse directions. Oscillation frequencies were correlated with vortex shedding frequencies, but low oscillation frequencies (sub-1 Hz), which were not apparently vortex- induced, were also present. Two $Re_{D}$ regimes were noted in which the vortex shedding frequency remained relatively constant with $Re_ {D}$,while the two regimes were separated by an intermediate transition region. This feature results in an apparently linear relationship between $St$ and $Re_{D}$ in each regime. Hydrogen bubble visualization showed strong three-dimensionality in the wake, as well as a diversity of wake structures varying with $Re_ {D}$.