A robotic fish is used to test the validity of a simplification made in the context of fish locomotion. With this artificial aquatic swimmer, we verify that the momentum equation results from a simple balance between a thrust and a drag that can be treated independently in the small amplitude regime. The thrust produced by the flexible robot is proportional to A2f2, where A and f are the respective tail-beat amplitude and oscillation frequency, irrespective of whether or not f coincides with the resonant frequency of the fish. The drag is proportional to , where U0 is the swimming velocity. These three physical quantities set the value of the Strouhal number in this regime. For larger amplitudes, we found that the drag coefficient is not constant but increases quadratically with the fin amplitude. As a consequence, the achieved locomotion velocity decreases, or the Strouhal number increases, as a function of the fin amplitude.
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Research Article| September 11 2018
Study of the thrust–drag balance with a swimming robotic fish
Christophe Raufaste ;
Yann Bouret ;
Médéric Argentina a)
Université Côte d’Azur, CNRS, Institut de Physique de Nice, 06100 Nice,
Institut Universitaire de France, 75005 Paris,
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Florence Gibouin, Christophe Raufaste, Yann Bouret, Médéric Argentina; Study of the thrust–drag balance with a swimming robotic fish. Physics of Fluids 1 September 2018; 30 (9): 091901. https://doi.org/10.1063/1.5043137
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