FLOW FIELDS GENERATED BY CASSIOPEA CONTRACTIONS: THE EFFECT OF ORAL ARMS ON FEEDING FLOWS

Abstract

Due to unprecedented reports of invasive jellyfish following high ocean temperatures, it is becoming increasingly important to understand how their presence in new areas changes surrounding waters. Cassiopea is a genus of invasive jellyfish that are a model organism for studying fluid dynamics. Cassiopea suction to the ocean floor, using their pulsing bells and oral arms to continually drive water upwards. To model the magnitude and directionality of their feeding flows through the fluid-structure interactions of the bell and oral arms driving fluid motion, I used simulations with the Immersed Boundary Finite Element (IBFE) Method. Prior work has neglected the prominent oral arms as a modeling simplification. This work is distinct in that the oral arms are included to represent a broad range of natural morphologies. The resulting simulations produce the deformation of the jellyfish bell and resulting fluid motion over seven pulses of the jellyfish bell across five distinct, biologically relevant oral arms models. Results show that inclusion of the oral arms significantly impacts the vorticity and vertical velocity of the currents. The simulations distinctly show the three phases of jellyfish movement and produce a vertical jet. Although the vertical et is not maintained due to the deflection of fluid by the oral arms, increased branching, decreased size, and added porosity and movement will enhance the upward flow.