Meeting Abstract

18.2  Thursday, Jan. 3  Optimal stroke patterns for a model jellyfish swimmer with thin, flexible body PENG, Jifeng*; DABIRI, John O; California Institute of Technology; California Institute of Technology jfpeng@caltech.edu

In this study, a numerical model is built to simulate swimming of oblate jellyfish (e.g. Aurelia aurita). The model swimmer is a thin, axisymmetric circular plate which is flexible and is able to deform, mimicking contraction and relaxation of a jellyfish. Using body deformation, the swimmer is able to swim by shedding vortices into fluid wake. The induced vortex flow from the swimmer is solved by an inviscid vortex sheet method (Shukla & Eldredge, Theor Comput Fluid Dyn 21, 343�368, 2007), which is capable of simulating unsteady separated flow from a deforming body. The numerical procedure is validated against the results of Shukla & Eldredge for computations involving a flapping flexible plate before applied to the jellyfish swimmer. The body kinematics are extracted from free-swimming Aurelia aurita and applied to the swimmer. The solved vortex wake is compared with the wake of the free-swimming Aurelia aurita measured by PIV. To study the effect of stroke pattern on swimming performance, the body kinematics are parameterized and optimized for minimal cost of locomotion. Optimization is performed using the surrogate management framework, which is chosen for its efficiency and rigorous convergence properties. The induced vortex wake structure from the optimal stroke pattern is studied and compared with those from non-optimal stroke patterns to identify the characteristics of the wake which enhance swimming performance. The study will provide knowledge on how the body kinematics of the jellyfish induce vortex flows which enhance swimming.