The body of the dolphin has low friction in water by having an optimal length to diameter ratio.

“The streamlined body of optimal shape has a length of 4.5 times its diameter. In this case the surface is smallest relative to the volume. This optimal numerical proportion has not remained a secret from nature: for dolphins (Tursiops gilli) the ratio is close to 5.” The author goes on to talk about the Reynolds number and how the shape of the dolphin shows high efficiency: “As a matter of fact, the maximal diameter of the dolphin is slightly back of center. Obviously, the above-mentioned effect was taken into consideration. Experiments have confirmed that this particular shape lowers friction drag in turbulent boundary layers to 65%.” (Tributsch 1983: 48)

Last Updated October 14, 2016