Title:

Underwater Flight of the Pteropod and Bio-inspired Design of Soft-material Robotic Swimmers

Speaker:

Dr. Donald Webster

Affiliation:

Georgia Tech, Civil and Environmental Engineering

When:

Monday, February 26, 2024 at 2:00:00 PM   Add to Calendar

Where:

MRDC Building, Room 4211

Host:

Alexander Alexeev
alexander.alexeev@me.gatech.edu

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 to 30 mm/s for pteropod size ranging 1.5 to 5 mm, and the pteropod shell pitches forward-and-backward at 1.9 to 3 Hz. The 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. The observed specimens swim within the same optimal Strouhal number range as observed for a broad range of species in air and water. Drawing inspiration from organisms, such as pteropods and manta rays, the hydrodynamics induced by deformation of magnetic-responsive soft material appendages are investigated. The effects of asymmetric multimodal actuation (i.e., folding versus bending) on the flow field are compared with the single actuation mode (i.e. bending only), by creating an asymmetric joint at the mid-point of the appendage. Further, the effect of non-symmetric time interval of positive/negative magnetic field generation is investigated on the flow field around the appendage. The findings demonstrate that utilization of symmetry-breaking morphology and an asymmetric cycle enhances stroke performance, offering promising avenues for achieving greater effectiveness in underwater robotic propulsion.

Biography

Donald Webster, Ph.D., P.E. is the Karen & John Huff School Chair and Professor in the School of Civil & Environmental Engineering (at the Georgia Institute of Technology in Atlanta, Georgia. Dr. Webster earned a B.S. in Mechanical Engineering from the University of California, Davis (1989), and M.S. (1991) and Ph.D. (1994) degrees in Mechanical Engineering from the University of California, Berkeley. He joined the Georgia Tech faculty in September 1997 after completing a postdoctoral research appointment at Stanford University and holding a non-tenure-track faculty position at the University of Minnesota. Dr. Webster’s research expertise lies in environmental fluid mechanics focused on the influence of fluid motion 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. His scholarly work has been highlighted numerous times by professional and media outlets. In recognition of these contributions, Dr. Webster is a Sustaining Fellow of the Association for the Sciences of Limnology and Oceanography (ASLO) and a Fellow of the American Society of Civil Engineers (ASCE). He has won numerous awards including the Felton Jenkins, Jr. Hall of Fame Faculty Award, Class of 1934 Outstanding Innovative Use of Education Technology Award, the Eichholz Faculty Teaching Award, and the British Petroleum Junior Faculty Teaching Excellence Award.