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 yonatanmunk@berkeley.edu

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.