Meeting Abstract

P1.202  Friday, Jan. 4  Limb drag during sand-swimming TAZ, H*; SHARPE, S/S; GOLDMAN, D/I; Wesleyan College; Georgia Institute of Technology; Georgia Institute of Technology hxtaz@wesleyancollege.edu

The sandfish lizard (Scincus scincus) buries into granular media like desert sand using body undulations and limbs. Once the animal is subsurface, the limbs are placed near the body and the animal propels itself using body undulation. We hypothesize that the sandfish does this to minimize drag. To test this prediction, we added simple limbs to a previously developed robotic model [Maladen et al, J. Royal Society Interface, 2011] of the sandfish. The body of the robot consisted of 6 servo- motors (HSR-5980SG) and these motors were controlled such that a single period approximately sinusoidal traveling wave propagated from head to tail. Without limbs, using similar wave kinematics to the animal, the robot achieved swimming performance (characterized by the wave efficiency η, the ratio of the forward swimming speed to the speed of the travelling wave), comparable to the animal. We added two forelimbs to the robot, located at approximately 30% of the robot’s body length (measured from the front) on either side of its body. Each limb structure consisted of a servo motor attached to a flat 8cm x 7cm plastic plate. The robot and limbs were covered in a spandex skin to prevent particles from jamming the motor joints. The addition of the limbs caused η to decrease from 0.34 (the value without limbs) to 0.28 ± 0.005, when the limbs were held parallel to the body. We next varied the angle relative to the body at which limbs were held (such that they extended away from the body midline). Increasing the angle from 0° to 90° resulted in a linear decrease in η, confirming our hypothesis that streamlining is possible in granular swimming. Future studies will actuate these limbs with different timing patterns to investigate how these limb structures could aid or disrupt the burial process.