Underwater Flight of the Pteropod: E201 Ocean Engineering Seminar Series

Seminar | March 22 | 2:30-4 p.m. | 3110 Etcheverry Hall

 Professor Donald R. Webster, Georgia Tech

 Department of Mechanical Engineering (ME)

Abstract: A portable tomographic particle image velocimetry (tomo-PIV) system was used to study fluid dynamics and kinematics of pteropods (aquatic snails nicknamed ‘sea butterflies’) in Antarctica. These pteropods (Limacina helicina antarctica) swim with a pair of parapodia (or “wings”) via a unique flapping propulsion mechanism that incorporates similar techniques as observed in small flying insects. The swimming velocity is typically 14 – 30 mm/s for pteropod size ranging 1.5 – 5 mm, and the pteropod shell pitches forward-and-backward at 1.9 – 3 Hz. It has been shown that pitching motion of the shell effectively positions the parapodia such that they flap downwards during both power and recovery strokes. The tomo-PIV measurements reveal the influence of the vortex structure created and shed from the parapodia on the generated lift forces. The non-dimensional variables characterizing the motion of swimming pteropods are flapping, translating, and pitching Reynolds numbers (i.e. Ref, ReU, and ReΩ). The observed specimens swim within the same optimal Strouhal number range as observed for a broad range of species in air and water. Further, we found that the relationship between these Reynolds numbers show an existence of a critical ReΩ, below which pteropods fail to swim successfully.

Biography: Dr. Donald Webster received his Ph.D. in mechanical engineering from the University of California at Berkeley in 1994. After a postdoctoral research position at Stanford University and a non-tenure track faculty position at the University of Minnesota, he joined the faculty at Georgia Tech in September 1997. For more than a decade, he has been part of the School's leadership team, serving as an affinity group coordinator 2012-2014, the associate chair for undergraduate programs 2007-2012, the associate chair for graduate programs 2012-2013, and the associate chair for finance and administration 2013-2018. In May 2018, he became the Karen and John Huff School Chair. Dr. Webster's research expertise lies in environmental fluid mechanics, with an emphasis on the influence of fluid mechanics and turbulence on biological systems. His contributions have been in three arenas: 1) illuminating the fluid mechanics processes related to sensory biology and biomechanics; 2) developing advanced experimental techniques and facilities; and 3) translating research results into bio-inspired design.

 makiharju@berkeley.edu, 510-642-1338