Passive and Active Flow Control by Swimming Fishes and Mamma

http://www.cadfamily.com/a/CAE_FEA_CFD/Fluid-Mechanics/Passive-and-Active-Flow-Control-by-Swimming-Fishes-and-Mamma_4196.html

Key Words
vorticity, locomotion, tubercles, digital particle image velocimetry,
flukes, biomechanics, hydrodynamics, biomimetic
Abstract
What mechanisms of flow control do animals use to enhance hydrodynamic performance? Animals are capable of manipulating flow around the body and appendages
both passively and actively. Passive mechanisms rely on structural and morphological
components of the body (i.e., humpback whale tubercles, riblets). Active flow control
mechanisms use appendage or body musculature to directly generate wake flow structures or stiffen fins against external hydrodynamic loads. Fish can actively control fin
curvature, displacement, and area. The vortex wake shed by the tail differs between
eel-like fishes and fishes with a discrete narrowing of the body in front of the tail,
and three-dimensional effects may play a major role in determining wake structure
in most fishes.