Improved Understanding of Biological Cavity-Jet Flows Using a Circulation Based Theoretical Pressure Model*

A novel technique for determining pressure inside deformable jetting cavities was recently derived (Krieg & Mohseni 2015) with respect to circulation dynamics. The use of such a model lies in the fact that circulation is an invariant for inviscid flows, hence circulation can be modeled as a series of sources and sinks. Therefore, this model allows high accuracy pressure calculation without solving for the full flow field, as long as the sources of vorticity are known. In this talk, the model’s usefulness is illuminated through analysis of complex biological systems including swimming of jellyfish, squid, and other animals. The accuracy of internal pressure calculated in these examples validates the model for low Reynolds number flows and complex body geometries, provided that the circulation generation is determined using inviscid models. Furthermore, the model also allows us to isolate different aspects of body deformation, identify the relationship to system circulation, and determine their contribution to the total propulsive output. Specifically, velar flap deformation is explained in terms of jet thrust and efficiency; as is the differences in squid and jellyfish internal geometry with respect to increases in propulsion vs respiration, respectively.