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Fluid-dynamic barrier for porosity-based propulsion and transport
In this talk, I present novel mechanisms of propulsion and passive transport in the flow regime where both inertial and viscous effects are important. In this flow regime, the porosity of the body can play a critical role for efficient motion. Such examples include microscopic insects whose wings are composed of many bristles with significant gaps between them. Despite the porous configurations, they fly successfully by forming virtual fluid-dynamic barriers inside the gaps, which are induced by strong viscous diffusion.
Using simplified two-dimensional cylinder-array models that represent the porous configurations, I explain how the development of the fluid-dynamic barrier determines the performance of propulsion and passive transport. First, for the array of multiple cylinders in a line, optimal arrangements are derived for uniform and unsteady free streams. Then, the reconfiguration of a poroelastic cluster and the coordinated active motion of multiple entities are examined. Lastly, I discuss future research directions for potential applications to powerless small-scale transporters.