TY - JOUR
T1 - Coherent locomotion as an attracting state for a free flapping body
AU - Alben, Silas
AU - Shelley, Michael
PY - 2005/8/9
Y1 - 2005/8/9
N2 - A recent experiment [Vandenberghe, N., Zhang, J. & Childress, S. (2004) J. Fluid Mech. 506, 147-155] has shown that an axle-mounted blade can spontaneously rotate when oscillated (or "flapped") above a critical frequency in a fluid. To understand the nature of flapping locomotion we study numerically the dynamics of a simple body, flapped up and down within a viscous fluid and free to move horizontally. We show here that, at sufficiently large "frequency Reynolds number," unidirectional locomotion emerges as an attracting state for an initially nonlocomoting body. Locomotion is generated in two stages: first, the fluid field loses symmetry by an instability similar to the classical von Karman instability; and second, precipitous interactions with previously shed vortical structures "push" the body into locomotion. Body mass and slenderness play central and unexpected roles in each stage. Conceptually, this work demonstrates how locomotion can be transduced from the simple oscillations of a body through an interaction with its fluid environment.
AB - A recent experiment [Vandenberghe, N., Zhang, J. & Childress, S. (2004) J. Fluid Mech. 506, 147-155] has shown that an axle-mounted blade can spontaneously rotate when oscillated (or "flapped") above a critical frequency in a fluid. To understand the nature of flapping locomotion we study numerically the dynamics of a simple body, flapped up and down within a viscous fluid and free to move horizontally. We show here that, at sufficiently large "frequency Reynolds number," unidirectional locomotion emerges as an attracting state for an initially nonlocomoting body. Locomotion is generated in two stages: first, the fluid field loses symmetry by an instability similar to the classical von Karman instability; and second, precipitous interactions with previously shed vortical structures "push" the body into locomotion. Body mass and slenderness play central and unexpected roles in each stage. Conceptually, this work demonstrates how locomotion can be transduced from the simple oscillations of a body through an interaction with its fluid environment.
KW - Bifurcation
KW - Flight
KW - Fluid-structure interaction
KW - Instability
KW - Symmetry-breaking
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U2 - 10.1073/pnas.0505064102
DO - 10.1073/pnas.0505064102
M3 - Article
C2 - 16055551
AN - SCOPUS:23844516492
SN - 0027-8424
VL - 102
SP - 11163
EP - 11166
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 32
ER -