2026 Yokokoji Viscoelastic Cantilever Wakes

Fluid-structure interaction (FSI) in viscoelastic flows past deformable structures at low Reynolds numbers is crucial yet poorly understood, particularly in biological systems such as cilia and engineered microsystems. This study investigates viscoelastic FSI in side-by-side flexible cantilever arrays through an experimental approach that varies the number of cantilevers and the rheology of test fluids, specifically comparing weakly shear-thinning and highly shear-thinning polyethylene oxide solutions. The research identifies a critical Weissenberg number at which weakly shear-thinning fluids transition from separated to merged elastic wakes, leading to coordinated cantilever deflections and a divergent flow field as the number of cantilevers increases. In contrast, highly shear-thinning fluids exhibit suppressed wake merger and inward deflection, indicating that elasticity alone is inadequate for collective instability. Instead, the interaction incorporating both shear-thinning properties and neighboring cantilever interactions is essential for such phenomena. The findings delineate the intricate interplay of fluid elasticity, shear-thinning behavior, and geometric configuration in governing viscoelastic FSI, establishing how elastic wake interactions influence array-scale structural responses during collective instability.