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The dispersion of indicator flowing through simplified models of the circulation and its relevance to velocity profile in blood vessels
Author(s) -
Caro C. G.
Publication year - 1966
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1966.sp007999
Subject(s) - mechanics , laminar flow , reynolds number , flow (mathematics) , pulsatile flow , hagen–poiseuille equation , secondary flow , cross section (physics) , volumetric flow rate , dispersion (optics) , secondary circulation , circulation (fluid dynamics) , materials science , physics , turbulence , optics , medicine , quantum mechanics , cardiology
1. The distribution of velocity (velocity profile) was studied in water flowing through simple models of the circulation. Dye was injected and the distribution of velocity was assessed from indicator concentration—time curves recorded with a photomultiplier. 2. Observations were made on straight and curved tubes and on a tube containing a short region with an elliptical cross‐section. With steady flow, the rate was varied over the range 24‐870 ml./min (Reynolds number 102‐3690). Sinusoidal pulsations were imposed on the steady flow in some experiments. 3. Bends gave rise to large secondary flows. These caused mixing across the flow and a marked reduction in the variation of velocity over the cross‐section of the tube. The effect of bends on velocity distribution was maximal at a Reynolds number of ca. 1000. Similar, but far smaller, effects were seen in a region with an elliptical cross‐section and when the flow was made pulsatile. Secondary motion due to bends was capable of preventing a heavier‐than‐water indicator (sp.gr. 1·375) from settling out of the flow. 4. The experimental findings suggest that there may be secondary flows in vascular beds. Under certain conditions, these would prevent the establishment of Poiseuille type laminar flow. The possible physiological importance of the findings is discussed.