| Summary: | Morphological adaptations that enhance swimming efficiency in fish have evolved over millions of years driven by the requirement to combine hydrodynamic efficiency with functional biology. Body induced vortices and the flow regime surrounding mature male blue sharks, Prionace glauca, are investigated in relation to the functional biology of the animal. Morphology was described using measurements from 5 North Atlantic specimens and the flow around these specimens was investigated using 3-dimensional computational fluid dynamics software (FluentTM). A k-epsilon turbulent model was used to represent the ocean flow regime and a number of different models represented the shark morphology (in order to reduce error induced by software limitations). Compared to control models (horizontal cylinders) the P. glauca body morphology increased the flow velocity on the body surface. The region around the gill slits showed a maximum relative velocity magnitude (increasing oxygen uptake efficiency) and the area of the lateral line adjacent to the dorsal fin showed the minimum. The effect of the dorsal fin on the flow regime was investigated using dorsal section models with and without the dorsal fin attached (and similar, half cylinder controls). The vorticity magnitude seemed to be enhanced by dorsal fin-body interactions along the adjacent section of lateral line. The results suggest that P. glauca body morphology acts to channel vortices along the lateral line, at a reduced relative velocity magnitude. This may allow for a greater abundance of superficial neuromasts and facilitate body-induced flow cancellation by the octavolateral nucleus, thereby enhancing the sensitivity of the lateral line in the low frequency range and enabling P. glauca to locate ambient water currents, such as the Gulf Stream, during migrations.
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