Inertia-driven fluid transport of a ciliary structure

Cilia play an important role in many biological systems. Although most cilia in nature are found in low Reynolds number, cilia of the high-Reynolds-number regime also exist. One example is cilia of a combjelly, which is known to have the largest cilia in animal kingdom. The length of these cilia is the order of millimetres, and they can induce irreversible flow in an inertia-dominant regime for propulsion and feeding.

To better understand the function of a ciliary structure, it is necessary to study the effect of Reynolds number in the wide range of O(1) – O(100) on the characteristics of fluid transport. For this aim, we conduct 2D simulation using the immersed boundary method, and, as a model, choose the symmetric motion of a simple ciliary structure. By identifying Lagrangian coherent structure using finite-time Lypunov exponent, we elucidate how the region of active fluid transport changes with Reynolds number. In addition, the symmetry breaking of cilia, which stroke symmetrically on two side walls of a channel, and its dependency on the Reynolds number are examined in the context of vortex-vortex interaction