Experimental and Theoretical Study of the Roles of Body Flexibility in Undulatory Bioinspired Swimmers*

Research has demonstrated that body flexibility is a determining parameter for oscillating objects in fluid flow. Understanding the role of body flexibility is crucial for many problems such as animal locomotion, robotics, and energy harvesting. In this study, we explore the impact of various parameters of swimmers with lateral undulation body motion on their swimming performance. In particular, the morphological parameters such as damping and stiffness and control policy parameters including effort and phasing are investigated. Here, the flow is modeled with Lighthill's elongated body model, and the structural dynamics are represented with a nonlinear large deformation viscoelastic beam model. We cross-compare the theoretical and computational results with corresponding results from towing tank experiments. A novel robot design used in these experiments is presented wherein the body stiffness is modified by changing the nominal fluid pressure, effectively developing antagonistic co-contraction of the silicone fluidic elastomeric actuators used along the body.