Concurrent measurements of the lift, drag, and time-resolved, 3D wake of finite-length cylinders in cross-flow at moderate Reynolds numbers

Aquatic environments are filled with organisms that sense and interact with their watery environment using finite-length, streamlining structures such as seal vibrissae (ie whiskers), marine mammal fur, and filamentous biofilms. The material compliance and geometry of these streamers influences how they interact with surrounding flow and can lead to widely varying dynamics. Experiments investigating the Fluid-Structure Interactions (FSI) of single finite-length cylinders in turbulent cross-flow were performed in the 12-inch variable pressure water tunnel at the Naval Surface Warfare Center, Carderock Division. Circular cylinders (D = 1 cm, L ~ 10 cm) were fabricated in a wide range of material compliance and their material properties and structural response characterized using tensile testing and Dynamic Mechanical Analysis (DMA). Cylinders representing large, simplified seal whiskers were also 3D printed and then evaluated in the 12-inch water tunnel at Carderock. The hydrodynamic behavior of the compliant circular cylinders and synthetic seal whiskers was determined from time-resolved measurements of their lift and drag across Reynolds numbers ranging from Re_D ≈ 5,000–75,000. Tomographic particle image velocimetry measurements were acquired concurrently with force measurements. Results reveal how compliance and specialized geometric features can lead to a variety of FSI behaviors.