Viscosity-enhanced fluid drift around hairy structures

Abstract

Hairy structures in nature function to sense smells and capture nutrients from surrounding fluid. Motivated by the complicated fluid transport processes observed in biological hairy structures, we numerically investigate the dynamics of fluid particles around multiple solid objects moving in a quiescent fluid, using simple two-dimensional cylinder models in the low-Reynolds-number regime (Re = 1–100). The behavior of fluid particles entrained by a moving cylinder array is analyzed by tracking particle trajectories and computing the drift volume, which indicates the amount of fluid particles transported by the moving cylinders. Hydrodynamic blockage of gaps within the cylinder array, which arises from the overlap of shear layers due to viscous diffusion, is critical in determining the overall fluid particle dynamics. As the number of cylinders increases, the deformation of the material line composed of fluid particles and the magnitude of the resultant drift volume show consistent patterns, despite undergoing drastic changes, and they converge to a specific configuration and magnitude, respectively. This study shows that visualization and quantification of collective fluid transport by multiple solid bodies are important to evaluate the efficiency of fluid transport for a collection of multiple bodies and to find its optimal configuration.