Eddy Formation and Turbulence in Flowing Liquids

Abstract

The birefringent properties of a colloidal solution of white Hector bentonite were used as a means of studying the development of flow patterns in transparent models. The liquid had approximately the same viscosity as blood; flow rates were within the physiological range; and some of the flow channels were shaped to resemble portions of the cardiovascular system. The light patterns produced by laminar flow were distinct from those of eddy formation and turbulence. Turbulent flow developed downstream from a constriction, where the velocities of the entering jet were much below the so-called critical Reynolds number. The same flow pattern was observed in a model of aortic stenosis. Also displayed was the flow pattern as it might develop in vivo during midsystole when the semilunar valves are widely opened. Eddies originating from the edges of the valves, the flow around the aortic arch and the effects of the openings of the branches all contributed to a complex turbulent pattern. Eddy formation and turbulence can be produced at low velocities when unsteady flow and sudden changes in diameter occur. This technique is useful in the study of changes in flow pattern under different physiological or pathological conditions. Observations from these models indicate that a more detailed analysis of flow conditions is both possible and worthwhile.