CFD study of aquatic thrust generation by an octopus-like arm under intense prescribed deformations

The complexity in structure and locomotion of cephalopods, such as the octopus, poses difficulties in modeling and simulation. Their slender arms, being highly agile and dexterous, often involve intense deformations, which are hard to simulate accurately, while simultaneously ensuring numerical stability and low diffusion of the transient motion results. Within the immersed-boundary framework, this paper focuses on an arm geometry performing prescribed motions that reflect octopus locomotion. The method is compared with a finite-volume numerical approach to determine the mesh requirements that must be employed for sufficiently capturing, not only the near wall viscous flow, but also the off-body vortical flow field in intense forced motions. The objective is to demonstrate and exploit the generality of the immersed boundary approach to complex numerical simulations of deforming geometries. Incorporation of arm deformation was found to increase the output thrust of a single-arm system. It was further found that sculling motion combined with arm undulations provides an effective propulsive scheme for an octopus-like arm.