Flow through an array of flexible hairs

Numerous biological systems rely on hair-like structures to filter or sense disturbances in their surroundings. These hair-like structures can cover external surfaces like in the lateral fish line or internal cavities such as cilia inside the oesophagus. Most of the elongated structures found in nature are flexible and deform when placed in a flow field. This observation is consistent with models of elastic beams that demonstrate their ability to act as strain sensors and amplifiers by deforming their substrate. This experimental study investigates the deformation of a flexible hair, isolated or in an array in a viscous flow. The experiments are conducted in a rectangular channel once a steady-state Poiseuille flow has developed in it. For the single hair, we vary the geometry and Young's modulus, and we measure the deformation of the hair and the surrounding flow field using particle image velocimetry. We then repeat the experiments with arrays of varying sizes, geometry, and hair spacing. We measure the flow field and hair deformation to model the effects of deformation on the flow through and around the array. Finally, we compare our experimental results with numerical simulations coupling the fluid flow and elastic deformation.