Moving Through Fluids
Physics sets effective constraints for biological evolution. The physics of fluid flow determine the operational range of swimming. ~ German biophysicists Johannes Baumgart & Benjamin Friedrich
Whether fish, turtle, bird, or cetacean, the selfsame efficiencies of animals in swimming can be characterized by a simple scaling law with 2 limits. The 1st limit is encountered at slower speeds, where the bulk of fluid resistance comes from skin friction, as water wants to adhere to an animal’s body. At faster speeds the 2nd limit appears, as resistance largely comes from pressure in front of and around the body.
Animal evolutionary biomechanics address these limits.
All swimming animals essentially reach the hydrodynamic limits of performance. There are general principles at work here. ~ Indian scientist Lakshminarayanan Mahadevan
Swimming and flying animals are optimally adapted for cruising through their environments, producing thrust via quite different propulsors: wings for flying and, in fish, caudal fins for swimming.
Since drag can never be completely eliminated, perfect efficiency is not possible. But animals have evolved to a narrow range of highly efficient parameters. ~ English naturalist Chris Packham