. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. FLUID MECHANICS OF AN ALGA 169 injector. FIGURE 2. Tracing from a photograph taken during injection of dye into the wake of a thallus; dye moves upstream, "peels oflT at the separation point, and marks the wake. The sting is idealized. Speed: m-s'1; fineness ratio: ratio" (length, over diameter), the latter ranging from to In short, separation occurred farther upstream in more rotund specimens. A variety of measurements of drag were made on thalli of Halosaccion, of which the most complete set
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. FLUID MECHANICS OF AN ALGA 169 injector. FIGURE 2. Tracing from a photograph taken during injection of dye into the wake of a thallus; dye moves upstream, "peels oflT at the separation point, and marks the wake. The sting is idealized. Speed: m-s'1; fineness ratio: ratio" (length, over diameter), the latter ranging from to In short, separation occurred farther upstream in more rotund specimens. A variety of measurements of drag were made on thalli of Halosaccion, of which the most complete set will be cited here; these were made on a particularly ordinary thallus and seem typical. The thallus had a length of cm and a volume (calculated from its mass) of cm3. Drag was measured at eleven speeds from to m-s"1, corresponding to Reynolds numbers (based on length) from 7450 to 44,100; data for drag were converted to drag coefficients (equation 2), with volume raised to the two-thirds power used as reference area. No discontinuities in the results were detectable; and, as will be discussed, the figures for drag were impressively low. The equation determined by the linear regression of log-transformed data for drag coefficient as a function of Reynolds number is Cd = 608 Re~°86, r = (9) How much force is, in fact, required to detach a thallus? Force to detach was measured for 20 thalli between and cm in length, all submerged while being pulled upon. Failure uniformly occurred at the stipe rather than the holdfast; ± N was required. Even the weakest attachment ( N) had a strength about six times the weight of the thallus, so hanging during emersion puts an alga at no hazard of detachment. Nor is the drag measured at the highest speed of the flow tank near values needed for detachment: N at m • s ' is more than a hundred-fold too low. Ambient flow and Iransmwal pressures In thalli, the concavities resulting f
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
