Forces and energetics of intermittent swimming
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Experiments are reported on intermittent swimming motions. Water tunnel experiments on a nominally two-dimensional pitching foil show that the mean thrust and power scale linearly with the duty cycle, from a value of 0.2 all the way up to continuous motions, indicating that individual bursts of activity in intermittent motions are independent of each other. This conclusion is corroborated by particle image velocimetry (PIV) flow visualizations, which show that the main vortical structures in the wake do not change with duty cycle. The experimental data also demonstrate that intermittent motions are generally energetically advantageous over continuous motions. When metabolic energy losses are taken into account, this conclusion is maintained for metabolic power fractions less than 1.
KeywordsUnsteady propulsion Burst and coast Bio-inspired
This work was supported by the US Office of Naval Research (Grant N00014-14-1-0533) (Program Manager Robert Brizzolara). We would also like to thank Dr. Keith Moored for stimulating our interests in intermittent swimming.
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