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Propulsion of a two-sphere swimmer

Klotsa, Daphne; Baldwin, Kyle A.; Hill, Richard J.A.; Bowley, R.M.; Swift, Michael R.


Daphne Klotsa

Kyle A. Baldwin

Richard J.A. Hill

R.M. Bowley

Michael R. Swift


We describe experiments and simulations demonstrating the propulsion of a neutrally-buoyant swimmer that consists of a pair of spheres attached by a spring, immersed in a vibrating fluid. The vibration of the fluid induces relative motion of the spheres which, for sufficiently large amplitudes, can lead to motion of the center of mass of the two spheres. We find that the swimming speed obtained from both experiment and simulation agree and collapse onto a single curve if plotted as a function of the streaming Reynolds number, suggesting that the propulsion is related to streaming flows. There appears to be a critical onset value of the streaming Reynolds number for swimming to occur. We observe a change in the streaming flows as the Reynolds number increases, from that generated by two independent oscillating spheres to a collective flow pattern around the swimmer as a whole. The mechanism for swimming is traced to a strengthening of a jet of fluid in the wake of the swimmer.


Klotsa, D., Baldwin, K. A., Hill, R. J., Bowley, R., & Swift, M. R. (2015). Propulsion of a two-sphere swimmer. Physical Review Letters, 115(24), Article 248102.

Journal Article Type Article
Acceptance Date Nov 6, 2015
Online Publication Date Dec 7, 2015
Publication Date Dec 11, 2015
Deposit Date Apr 21, 2017
Publicly Available Date Apr 21, 2017
Journal Physical Review Letters
Print ISSN 0031-9007
Electronic ISSN 1079-7114
Publisher American Physical Society
Peer Reviewed Peer Reviewed
Volume 115
Issue 24
Article Number 248102
Public URL
Publisher URL
Additional Information Propulsion of a Two-Sphere Swimmer. Daphne Klotsa, Kyle A. Baldwin, Richard J.?A. Hill, R.?M. Bowley, and Michael R. Swift. Phys. Rev. Lett. 115, 248102.


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