Middle fins hold the key to fish movement

Next time you find yourself in an aquarium, pay attention to the fish's fins. The middle fins particular show a mesmerising variety number, shape and position on body. But what is purpose of such variation? David Matthews George Lauder Harvard University aimed address this question by investigating interactions between tail their effect movement. Biologists engineers have previously attempted navigate these tough waters, so new angle did pair introduce?Matthews used simplified fish-like robotic model: thin plastic foil mimicking proportions form fish (a body, fin two symmetrically arranged either side body) connected flapping device introducing sideways movement with help motors. This model was step closer real than previous mechanical models, which just forces produced were investigated. On top that, they decided not control every aspect movement, would overcomplicate robot-fish, but measure them instead. They attached force-sensing rod front foil, where head be, changed number cycles body experienced per second propel itself forward. Using setup, could quantify foil's energy as its speed maximum amount each flaps respectively, all together determining swimming performance fish.With robot-fish at hand, authors first asked how timing flapping, i.e. whether flap unison or not, affect performed experiments four types robot-fish: flexible stiff, near far from tail. then showed that has largest performance, consistent live more often when want accelerate. modelling also revealed stiffness didn't significantly change while location did. far-fin always fastest, moving out sync fin, it most efficient. team observed beneficial for force production, varied less over time, costing fish.To understand results further, visualisation technique look water flow around having helpful strong side-to-side – irrespective foils. In contrast, found stiffer foils, one resulted direct interaction amplifying production propelling force. Thus, able conclude patterns amplification are statistical can explain why production. As result, we knew impact following individuals, now know independently improve using secret weapon