Swimmers use two general strategies: steady-speed (e.g. fish) versus unsteady ‘burst-and-glide’ swimming (e.g. frogs). While scientists have studied fish hydrodynamics to improve speed and efficiency in robots, frog propulsion has largely been neglected. Unlike fish, frogs have evolutionarily co-opted powerful jumping muscles to generate large fluid forces as they kick. Additionally, theory predicts that certain frogs amplify thrust via a central water jet as the legs whip together during kicking. We aim to quantify fluid dynamics on living and robotic frogs to test this ‘central jet theory’ and to discover additional unsteady fluid mechanisms that enhance swimming performance.
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