. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 2 3 time (sec) C 0) o o time (sec) D o time (sec) .85 Figure 5. Comparison of thrust generated by the model (dotted lines) with thrust calculated only on the basis of the angular position of the model (solid lines). Each graph represents a single stroke of the model, although the force is averaged over all strokes during the 100 runs (and total stroke number depends on the frequency and speed). Arrows mar
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 2 3 time (sec) C 0) o o time (sec) D o time (sec) .85 Figure 5. Comparison of thrust generated by the model (dotted lines) with thrust calculated only on the basis of the angular position of the model (solid lines). Each graph represents a single stroke of the model, although the force is averaged over all strokes during the 100 runs (and total stroke number depends on the frequency and speed). Arrows mark onset of recovery stroke. A-D correspond to the four successive larval stages the model mimics (see Table I). In C and D there is an offset due to greater translational speeds. thrust on oscillator.' propulsors (, Nachtigall, 1974), Blake (1985) has shown that they may produce as much as one-third of the thrust on the limbs of water boatmen, Cenocorixa hifida. The Reynolds number of these animals is about two orders of magnitude higher than those ex- perienced by Anemia larvae modeled here (600 vs. 1-9), so it is not surprising that unsteady forces are correspond- ingly greater. Although the model does not capture all of the details of the animal's limb kinematics, it does provide some generalizations about oscillating propulsion. In an over- view of swimming in crustaceans. Hessler (1985) hypoth- esizes that setal structures on diverse swimming limbs may extend passively. Such passive extension is the case for the feeding setae of a filter-feeding shrimp (Fryer, 1977). This passive behavior may be possible only in some hy- drodynamic regimes. At the intermediate Reynolds num- bers modeled here, comparison of the thrust generated by the model at low and high Strouhal numbers suggests that an animal could use passively extending setae only if the speed of limb oscillation is high relative to the forward speed of the body—otherwise a passively extending system provides li
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
