Abstract.
Fast swimming sharks have small riblets on their skin, which are assumed to improve the swimming performance of the fish. Fluid dynamic experiments in water as well as in air confirm this assumption. With riblet surfaces as compared to smooth surfaces, drag reductions up to about 10% were measured. The overall riblet pattern on sharks shows parallel riblets directed from head to tail, but besides this overall pattern fast swimming sharks have also small areas with converging riblets and others with diverging riblets. In the present study the velocity field over convergent and divergent riblet patterns is investigated by hot-wire measurements in turbulent pipe flow. Significant changes in the near wall velocity field were found.
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Koeltzsch, .K., Dinkelacker, .A. & Grundmann, .R. Flow over convergent and divergent wall riblets. Exp Fluids 33, 346–350 (2002). https://doi.org/10.1007/s00348-002-0446-3
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DOI: https://doi.org/10.1007/s00348-002-0446-3