. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 10 M. DENNY AND L. ROBERSON Flow-exposed crest, Re = 20,000. -25 -20 -15 -10 -50 5 10 15 20 25 Angle of Incidence (degrees) Figure 11. Angle-specific flux from the crest of a flow-exposed blade at Ret = 20,000. Open circles show the static response of the model; filled circles, the dynamic response. The vertical bars are the standard deviation of measurements among seven cycles, an index of the intensity of turbulent mixing over the model. The arrows indicate the order in which angles were achieved during a cycle of pitching
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 10 M. DENNY AND L. ROBERSON Flow-exposed crest, Re = 20,000. -25 -20 -15 -10 -50 5 10 15 20 25 Angle of Incidence (degrees) Figure 11. Angle-specific flux from the crest of a flow-exposed blade at Ret = 20,000. Open circles show the static response of the model; filled circles, the dynamic response. The vertical bars are the standard deviation of measurements among seven cycles, an index of the intensity of turbulent mixing over the model. The arrows indicate the order in which angles were achieved during a cycle of pitching. negative angles of incidence. When the angle of incidence is increasing, dynamic flux at negative pitch is similar to static flux, but is greater than static flux for positive angles of incidence. The reason for the similarity of the flux pattern between the flow-exposed blade at high Re, and the flat plate at low Re, is not readily apparent. High flux values for the blade are not associated with high standard deviations of flux. Thus, the explanation invoked for the flat plate at low Re, (temporal hysteresis in the creation and subsequent dissipation of turbulence in the plate's wake) is unlikely to apply to the flow-exposed blade. Cyclic average static flux to the flow-exposed blade at Re, = 20,000 () is about times that at Re,. = 2700 (). Dynamic flux at high Re, () is times that at lower Re, (). The ratio of dynamic to static flux at high Rev is for the flow-exposed blade, apparently slightly lower than that at Re, = 2700 (), although we have again not attempted to attach a level of statistical confidence to the difference of these ratios. Overall flux versus static angle In steady, unidirectional flow, a kelp blade may be ori- ented at a fixed pitch angle. In this case, the overall flux to the blade can be estimated from our measurements as the sum of the static flux to the blade's upstream and down- stream faces at that angle relative
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
