1. Drag force ratio dependence on flow speed and dimensionless denticle ridge spacing for turbulent flows.
Drag force ratio dependence on flow speed and dimensionless denticle ridge spacing for turbulent flows.Ds/Dm is the ratio of static drag of the smooth foil (Ds) to static drag of the shark skin foil (Dm). (A) Dependence on the flow speed (U). (B) Dependence on dimensionless denticle ridge spacing for turbulent flows (turbulent S+). The red solid lines represent Ds/Dm=1, which indicates that the synthetic shark skin foil has the same static drag force as the smooth foil. The vertical dashed lines in A and B indicate ‘critical’ flow speed (U*) and critical S+ (S+*), respectively, where drag of the shark skin membrane is greater than that of the smooth control. Drag forces are means from N=5 trials for each measurement, which lasted 20 s. Error bars are ±1 s.e.m., and are the same for A and B. For further explanation, refer to the Materials and methods. Drag force values for the shark skin and smooth control membranes are provided in Table 1.
Li Wen et al. J Exp Biol 2014;217:
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