The science behind swimming: From whales to larvae, common principles at work in swimming

The blue whale is the largest mammal on the planet, fish larvae are one of the smallest aquatic animals on the planet. The question is how do these two extremes both propel themselves through the same water. L. Mahadevan of the  Lola England de Valpine Professor of Applied Mathematics, of Organismic and Evolutionary Biology, and of Physics and her team used simple hydrodynamics to develop a handful of principles to govern how virtually every animal propels themselves through water. This what Mahadevan had to say "What we wanted to investigate was how the speed of an organism changes as a function of how large it is, how quickly it moves and how much it moves," "To resolve that in detail, however, is very complex, because there is a great deal of differences in morphology and what parts of the body different creatures use to swim. The question is: Is there anything in common across all these organisms? The answer, we found, is yes." Steering away from the traditional route which is to accurately characterize a group based on experiments and simulations the team decided that theres no need for that since they all swim in the same water.

 Next came the biology factor which led to an algebraic equation to account for 50 years of experiments. The variables were: input variables -- namely the size of the organism, the amount an organism moves and how quickly it moves -- control the output variable, which is effectively the speed at which it moves. What this showed was the relationship can be explained with two limits. The first, which corresponds to creatures moving at intermediate speeds, describes situations where the bulk of the resistance is caused by skin friction, because water "sticks" to the organism's body. At faster speeds, Mahadevan said, the resistance organisms face largely comes from pressure that builds up in front of and around them, which is described by the second limit."While it wasn't a surprise that the resistance changed at organisms moved faster, the fact that those challenges could be so simply described was interesting and provocative, because we are talking about organisms that range in size from a few millimeters to the size of a blue whale," Mahadevan said  The researchers found that the swimming speed of virtually every organism, from fish larvae to frogs to birds, amphibians and even whales, could be described by one of the two equations. http://www.sciencedaily.com/releases/2014/09/140915102113.htm