Meeting Abstract

S1-2.4  Jan. 4  Reactive Forces in Undulatory Swimming, with Reference to the Common Garter Snake (Thamnophis sirtalis) MUNK, Y.; Univ. of California, Berkeley

Classical studies of the swimming of long and narrow animals have treated anguilliform propulsion as driven largely by resistive (drag-based) forces acting on the body, with ‘reactive’ forces (resulting from the acceleration reaction force) generated solely at the tail as predicted by Lighthill’s elongated body theory. This separation of resistive and reactive forces is strictly only valid when the undulatory waves propagate along the body with constant speed; however, it has been previously noted that many swimming snakes exhibit an accelerating propulsive wave. I have digitized the kinematics of swimming garter snakes (Thamnophis sirtalis) from high speed video and used nonlinear regression techniques to demonstrate conclusively that there is a significant increase in the propagation speed of the undulatory wave as it moves rearward along the animal. I will explain how this phenomenon contributes a component to the total thrust via acceleration reaction forces, and discuss the circumstances under which this phenomenon should be considered in general.