Simulation of an energy harvesting eel by the immersed boundary method

Abstract

In the present study, we carry out numerical simulations of energy harvesting eel by using the immersed boundary method. The fluid motion is described by Eulerian variables defined on a fixed Cartesian mesh, while the filament motion is described by Lagrangian variables defined on a freely moving mesh. Eel is modeled by a flexible filament and is placed behind a circular cylinder. We perform systematic simulations in order to explore the effects of Reynolds number, filament mass, bending coefficient of filament, gap distance between cylinder and filament and filament length. The instantaneous filament motion is analyzed under different conditions and the surrounding vortical structures are identified. The flapping frequency of energy harvesting eel was compared with that in case of cylinder alone as well as filament alone. As increasing Reynolds number, we can see that the Strouhal number of cylinder alone is almost the same as that of energy harvesting eel, indicating that the filament flapping is passively induced by the vortical structures behind the cylinder. The bending energy is calculated for different conditions.