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Advantages of High Reynolds Number Swimming: Insights into Propulsion Efficiency

Today's lecture in Integrative Marine Sciences (SMS 204) focused on high Reynolds number swimming, exploring how different modes of propulsion—axial, appendage-based, and jet propulsion—affect efficiency. We discussed the impact of slope in measured data for viscosity, and highlighted the benefits of streamlining, which minimizes boundary layer separation and wake turbulence. A review session included class evaluations and an engaging discussion on the physics behind thrust and drag in swimming, alongside practical applications in robotics.

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Advantages of High Reynolds Number Swimming: Insights into Propulsion Efficiency

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  1. SMS 204: IMS II • Today’s lecture: High Reynolds number swimming. • Homework: • Unit conversion affected ability to do the homework correctly. • Slope with measured data matched reported values for viscosity very well! • Today: lecture + class evaluation + review for exam (pizza). • ‘What’s for lunch’ & Soja/Andy/Ruth co-winners! SMS 204: Integrative marine sciences

  2. High Re swimming. What should we expect? • Modes of swimming: • Axial propulsion • Appendage-based propulsion • Jet propulsion Movie SMS 204: Integrative marine sciences

  3. Advantage of streamlining at high Re # swimming: No boundary layer separation. Minimal wake.

  4. Axial undulatory propulsion • The axial structures are used (vertebral column and associated musculature) • Mostly primary swimmers (evolved from aquatic ancestors). • Use undulations of the body (pass them from anterior to posterior along the body) to generate thrust SMS 204: Integrative marine sciences

  5. Physics of swimming: Thrust Drag • Maximize • Minimize Wikipedia: Thrust is a reaction force described quantitatively by Newton's Second and Third Laws. When a system expels or accelerates mass in one direction the accelerated mass will cause a proportional but opposite force on that system.

  6. How is thrust generated? Similar motion in the vertical (e.g. dolphin) generates lift as well as forward thrust. SMS 204: Integrative marine sciences

  7. Vortex shedding: Reduced drag (keeps boundary layer attached). Increased efficiency as jet provides thrust.

  8. SMS 204: Integrative marine sciences

  9. Appendage-based propulsion Undulatory appendage-based propulsion • Traveling waves are generated that sweep down the fin • Thrust is generated in the same way as for axial undulatory propulsion Drag-based propulsion • Appendages operate like an oar or paddle • Two phases to the fin beat cycle • Power stroke — the appendage is pulled backward through the water. • Recovery stroke — the appendage is pulled forward through the water. SMS 204: Integrative marine sciences

  10. SMS 204: Integrative marine sciences

  11. Drag  lift Surface  subsurface SMS 204: Integrative marine sciences

  12. Jet propulsion SMS 204: Integrative marine sciences

  13. Approaches to study swimming • High speed visualization and experimentation: http://darwin.bio.uci.edu/%7Eedrucker/home/Movie%20pages/perch_warning.htm SMS 204: Integrative marine sciences

  14. Approaches to study swimming • Mathematical models: Example: tubercles of humback whales, Fish and Lauder, 2006. SMS 204: Integrative marine sciences

  15. Mathematical modeling: Wind tunnel experiments:

  16. Approaches to study swimming • Analogue models  Robots • Another newer robot SMS 204: Integrative marine sciences

  17. Why should engineers study swimming? We have a lot to learn from nature: % fuel energy converted to motion

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