Pressure versus flow in biological pumps.
The pumps with which organisms move fluids span nearly a ten-million-fold pressure range. As in human technology, positive displacement pumps (osmotic, valve-and-chamber, peristaltic, etc.) are used for high-pressure applications and fluid dynamic pumps (using hydrofoils, cilia, aspirators, etc.) for low pressures. But while pressure capability or system resistance dichotomizes pumps by operative mechanism, the values of a dimensionless pressure-flow index prove more relevant to their biological roles; this index is a ratio of overall pressure drop in the system to pressure drop due to viscous resistance to flow.
Vogel
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Department of Zoology, Duke University, Durham, NC 27708, USA.
D000818:Animals; D001693:Biological Transport, Active; D055592:Biophysical Phenomena; D001703:Biophysics; D008954:Models, Biological; D011312:Pressure; D014783:Viscosity