Combining high-speed planar PIV and motion tracking of a flexible cylinder in cross-flow

Most modeling studies investigating the flow dynamics in vegetation canopies are limited to rigid models. However, most canopies embody some degree of structural flexibility, resulting in flow-structure coupling. Studies addressing flexible canopies typically quantify either the flow or the plant motion independently. To this end, high-speed PIV data of the flow surrounding an idealized canopy element, consisting of a flexible cylinder, together with the solid displacement field were simultaneously obtained by combining fluorescent imaging and refractive index matching (RIM). The RIM approach involved matching the RI of an aqueous solution of sodium iodide (NaI), used as the working fluid, with that of the solid model fabricated from a clear polyurethane rubber. The operating principle of the technique employed involves seeding the two phases with different tracers (the flow with silver-coated glass spheres and the cylinder models with fluorescent particles), facilitating independent interrogation of the dynamics of each. This time-resolved data allowed for observation of the dynamic link between a deformable object and the surrounding flow. The experimental method may be extended to other geometries and aid in the study of aeroelastic flow–structure interactions.