Meeting Abstract
Unlike many bird and insect wings, the fins of fishes have a very low aspect ratio: their span is small compared to their chord length, while many wings have a wide span and short chord length. For fishes, this means that the flow that wraps around, above and below the body and fins can have a large impact on the flow near the horizontal midline. This effect should be particularly important for elongate fishes like lampreys. However, most previous studies of the flow patterns around fishes have used planar two-dimensional particle image velocimetry (PIV), a technique that resolves two components of the velocity vector in a plane. While useful, this approach provides little insight about the 3D flow patterns that must be important for the low aspect ratio fins and bodies of fishes. For elongate fish such as the long and approximately cylindrical lamprey, 3D information is essential to characterize how these fish interact with their fluid environment. This study presents 3D flow structures along the body and in the wake of larval lamprey, Petromyzon marinus, which are 10-15 cm long. Lamprey swam through a 1000 cm3 field of view in a custom made 60 cm long by 10 cm deep plexiglass tank, illuminated by a 532 nm wavelength green laser. Data were collected using a three component velocimetry V3V system by TSI, Inc. and processed using Insight 4G software. This study expands on previous works that show two pairs of vortices each tail beat in the mid-plane of the lamprey wake.
