Sea lion swimming: a model for efficient, hydrodynamically quiet propulsion
Abstract
Sea lion swimming: a model for efficient, hydrodynamically quiet propulsionThe objective of this project is to determine a mechanism for high-performance jet-like swimming based on the California sea lion, a highly maneuverable aquatic mammal that produces thrust primarily with its fore flippers. To understand sea lion hydrodynamics,we must first characterize its kinematics. Previous efforts to do so, which inform this work, do not include quantitative descriptions of the relevant parameters for a detailed, controlled hydrodynamic study. At this time, we propose to conduct a comprehensive field study the Smithsonian National Zoological park (SNZ) in Washington, DC. This study will provide us with a digital catalog of sea lion maneuvers and a detailed mathematical description of them. The study will initially focus on steadyswimming behavior (the ~clap~) before progressing to include turning, accelerating and other advanced maneuvers. We will obtain both two- and three-dimensional data using three synchronized digital cameras. This required significant development of markerless three-dimensional tracking techniques for large free-swimming bodies.Once we gather kinematic data, we will look to replicate a hydrodynamically quiet unsteady proposulor in a laboratory setting. While observational data of swimmingsea lions offers insight into such propulsion, it is not sufficient to understand its hydrodynamic effects on the surroundings. The work proposed here will lay thepreliminary foundation for the design and construction of a robotic sea lion fore flipper.Finally, high-magnification images of the propulsive surface will let us investigate its natural flow control abilities. As mammals, sea lions are covered in hair. On the foreflipper, the main propulsive surface, the amount and type of hair varies significantly with location, we will explore the connection of these structures to the flow in these areas with regard to drag reduction and flow control.This project is a natural, innovative extension of work on unsteady propulsion that has been carried out over the last decade. However, unlike previous results, whichindicate that efficient underwater thrust production is accompanied by a strong coherent wake, the sea loin offers a potential paradigm wherein efficient, effective propulsion does not have to leave this highly traceable signature. Thus, it has the specific potential for creating efficient, stealth underwater propulsion, an expressed mission of the Office of Naval Research (ONR).This project will have a strong scientific contribution, both in the physics that will be explored and the methods that will be developed. The main method development is markerless, three-dimensional tracking of a large, freely swimming object. While methods exist for small-scale motion (insects) or highly predictable motions (human walking), these tools are not available for general locomotion with an unknown trajectory. The physics we will explore, the efficient, pulsatile swimming of the sea lion, will investigate a new paradigm of high performance biologically inspired locomotion.Finally, by exploring the surface features of the foreflippers and connecting them to the active and passive flow control of those structures, we will provide insight into the complex connection of micro and macro scales in unsteady propulsion.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 05, 2017
- Source ID
- N000141712448
Entities
People
- Megan C. Leftwich
Organizations
- George Washington University
- Office of Naval Research
- United States Navy