Flow Through Collapsible Tubes: Augmented Flow Produced by Resistance at the Outlet

Abstract

The physical laws describing the character of flow through blood vessels may depart radically from those which have been developed by engineers and physicists for uniform flow through rigid tubes of uniform diameter. These deviations are marked in the case of flow through collapsible tubes,such as blood vessels and valves. At critically high velocities, the flow pattern may be transformed from a quiet, uniform smooth-flowing stream to an interrupted series of jets with the production of audible sound and with marked energy losses. The present study deals primarily with the "paradoxically" increased flow which may take place through collapsible tubes when a resistance is added to the outlet from the system. This marked deviation from the laws for rigid tubes is attributed to the vessel-distending effects of the added resistance, and to the inhibition of the phenomenon of recurrent collapsibility. The present in vitro experiments are used to attempt to explain certain paradoxical findings in flow through the collapsible tube systems of the body.