RoboKrill: the role of morphology on thrust production during metachronal swimming

Metachronal, drag-based swimming in krill (\textit{E. superba}) has been studied to understand its ecological significance and find optimal engineering solutions for underwater locomotion. Krill modulate the profile area of their appendages while maintaining a phase shift between appendage pairs resulting in efficient propulsion in the intermediate Reynolds number (Re) regime. Previous studies have informed many aspects of krill swimming. However, the connection between thrust production and vortex generation remains largely unexplored. Leveraging our recently developed Robokrill, we performed velocimetry experiments to understand the hydrodynamic effects of morphological traits during forward-swimming. In particular, we focus our study on the role of setae, which are flexible hair-like structures. By broadening the profile area of the appendages, setae promote the production of thrust by increasing the area enclosed by generated vortex structures. Exploring morphological traits allows us to understand the design parameters behind efficient propulsion at intermediate Re. Going forward, we aim to identify unifying success mechanisms of different species of drag-based swimmers to engineer a new generation of underwater robots.