  Mathematical and experimental studies of the flows generated by jellyfish
have focused primarily on mechanisms of swimming. More recent work has also
considered the fluid dynamics of feeding from currents generated during
swimming. Here the benthic lifestyle of the upside down jellyfish (Cassiopea
spp.) is capitalized upon to explore the fluids dynamics of feeding uncoupled
from swimming. A mathematical model is developed to capture the fundamental
characteristics of the motion of the unique concave bell shape. Given the
prominence of the oral arms, this structure is included and modeled as a porous
layer that perturbs the flow generated by bell contractions. The immersed
boundary method is used to solve the fluid-structure interaction problem.
Velocity fields obtained from live organisms using digital particle image
velocimetry were used to validate the numerical simulations. Parameter sweeps
were used to numerically explore the effects of changes in pulse dynamics and
the properties of the oral arms independently. Numerical experiments allow the
opportunity to examine physical effects and limits within and beyond the
biologically relevant range to develop a better understanding of the system.
The presence of the prominent oral arm structure in the field of flow increased
the flux of new fluid from along the substrate to the bell. The numerical
simulations also showed that the presence of pauses between bell expansion and
the next contraction alters the flow of the fluid over the bell and through the
oral arms.
