Bio-inspired forward and backward swimming gaits resulting from fluid-structure interactions

Biological undulatory swimmers display a wide range of gaits and are adept
at swimming in different directions. This study explores the impact of
passive dynamics as a result of fluid-structure interaction on the gaits
of a model swimmer through computational simulations. Inspired by
slender-bodied natural aquatic swimmers, the model consists of a flexible
body and a rigid head. Systematically varying body stiffness and head
pitching, the research replicates various swimming patterns observed in
nature (both forward and backward). Optimal forward gaits, akin to
anguilliforms and carangiforms, result from low to high bending rigidity
and small pitching amplitudes. Conversely, low bending rigidity with high
pitching amplitude produces backward swimming (tail-first), similar to
mosquito larvae, exhibiting unique flow-field features and generating
backward propulsion forces. The study underscores the significant role of
passive dynamics in undulatory swimming and the potential for diverse gait
generation through tailored structural and kinematic design in
bio-inspired devices.