Meeting Abstract

13-3   11:00 - 11:15  Simulation of snakes traversing a wedge obstacle using vertical body bending Zhang, Y*; Xuan, Q; Li, C; Johns Hopkins University; Johns Hopkins University; Johns Hopkins University yzhan401@jhu.edu http://li.me.jhu.edu

Snakes are excellent at slithering across a variety of terrain. Many studies focused on how snakes use lateral body bending to generate propulsion against asperities on flat surfaces. Only recently did we realize that snakes can also use vertical bending to propel against terrain of varying height, such as a horizontal ladder and a wedge (Jurestovsky, Usher, Astley, 2021, JEB) or uneven terrain (Fu, Astley, Li, 2021, SICB). Here, to understand how to use vertical bending to generate propulsion, we developed a dynamic simulation of snakes traversing a wedge obstacle (slope = 27°, length = 0.1 body length, similar to animal experiment), using a recent numerical discrete elastic rods method (Zhang et al, 2019, Nat. Comm.). The snake was modeled as an elastic Cosserat rod, which can bend itself by internal forces. The interaction between the snake and terrain was modeled via a spring-damper model for normal force plus Coulomb friction. The rod is governed by internal forces including tensile/compressive, shear, bending, twisting forces due to deformation, internal torque given by a controller, and external forces including terrain reaction forces and gravitational force. We found that a posteriorly propagating internal torque profile with a maximum on body segments around the wedge obstacle generated near steady-speed forward locomotion as observed in the animal, with torque magnitude insensitive to locomotion speed. Remarkably, for a snake-terrain kinetic friction coefficient of only 0.20, the body had to push into the sloped wedge surface with a pressure as high as 5 times that from body weight to generate sufficient forward propulsion to overcome frictional drag. This suggested that snakes have a large capacity to use vertical bending to push against the environment to generate propulsion. We are performing systematic parameter variation in our simulation to discover propulsion principles.