Analytic Modeling of a Size-Changing Swimmer

Abstract

Cephalopods use large-scale structural deformation to propel themselves underwater, changing their internal volume by 20–50%. In this work, the hydroelastic response of a swimmer comprised of a fluid-filled elastic-membrane is studied via an analytic formulation of two coupled non-linear dynamic equations. This model of the self-propelled soft-body dynamics incorporates the interplay of the external and internal added-mass variations. We compare the model against recent experiments for a body which abruptly reduces its cross-section to eject a single jet of fluid mass. Using the model we study the impact of size-change excitation on sustained swimming speeds and efficiency.