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Wall Drag on Free-Moving Ciliated Micro-Organisms

Winet, H. (1973) Wall Drag on Free-Moving Ciliated Micro-Organisms. Journal of Experimental Biology, 59 (3). pp. 753-766. ISSN 0022-0949.

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It is generally assumed that wall drag on free-moving, self-propelled or passively moving micro-organisms is not significant under normal observation conditions. Yet the point at which such drag becomes significant has not been determined quantitatively. By comparing the relative velocities of sinking as well as swimming ciliates in tubes of various bore widths it has been determined that wall drag on sinking cells is about 8% significant at 108-132 body radii (or minor semi-axes) from the cell surface while the corresponding range for swimming cells is less than 1-4·2 body radii. These results are compared with the mathematical approximations for Stokes radius R_8 and depth of penetration of diffusing vorticity δ which characterize steady and quasi-steady Stokes flow respectively around a solid body. It is found that the asymptotic nature of the velocity profile of steady flow is reflected in the lack of agreement between R_8 and the measured distance for 8% drag. Conversely, the sharp gradient (or propulsive envelope) of the quasi-steady velocity profile is reflected in the substantial agreement between δ and the measured distance for > 0% drag. It is suggested that the given formula for δ which includes allowance for a propagated wave is a valid measure of the thickness of the quasi-steady region and that observations on motile ciliates be restricted to organisms at least 4 cell radii from the nearest wall if measurements free of wall-drag effects are to be obtained.

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Additional Information:© 1973 The Company of Biologists. Received 22 May 1973. The author is indebted to Mr Long Wa Lee and Mr Stuart R. Keller for their assistance in performing the experiments. This investigation was supported by Grant GK31161X from the National Science Foundation and Contract N00014-67-A-0094-0012 from the Office of Naval Research.
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Office of Naval Research (ONR)N00014-67-A-0094-0012
Issue or Number:3
Record Number:CaltechAUTHORS:20120814-100400993
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Official Citation:H. WINET Wall Drag on Free-Moving Ciliated Micro-Organisms J Exp Biol 1973 59:753-766.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:33158
Deposited By: Ruth Sustaita
Deposited On:14 Aug 2012 17:23
Last Modified:03 Oct 2019 04:07

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