Computational Study of 2D Jellyfish with the Immersed Boundary Method

Mahdi Salehzadeh

Jellyfish possess the most efficient method of movement of any animal on Earth, despite their simple physical and neural makeup, making them a popular model organism for biologists. Despite numerous experimental and computational studies aimed at understanding their swimming dynamics and performance, there is still much to learn about these creatures. This research employs numerical simulations using the immersed boundary method to investigate the fluid-structure interaction between a 2D model of a swimming jellyfish and its surrounding fluid. Specifically, we focus on jet-like swimming observed in prolate jellies that periodically contract their bell muscles to expel water from their interior. By analyzing the scaling properties of jellyfish using two dimensionless parameters – the Reynolds number and swimming number – we demonstrate that a power-law dependence derived for undulatory swimmers extends naturally to jellyfish using jetting propulsion. We also investigate the feeding technique used by jetting swimmers, which involves exploiting trailing vortices generated by bell contractions to redirect passive prey such as algae and plankton into their bell interior. Our numerical simulations enable us to examine the effects of changes in prey distribution and jellyfish size and shape in detail which is typically not possible in experiments. Finally, we explore pair-wise interactions between jellyfish, where nearby swimmers generate repulsion forces and turning responses when they come into close proximity. The ultimate goal of this research is to establish a foundation for future computational simulations of swimming and feeding dynamics in swarms of interacting jellyfish.

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