Accelerated and Decelerated Flows in a Circular Pipe : 1st Report, Velocity Profile and Friction Coefficient

概要

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In order to determine the flow characteristics of a transient flow in a circular pipe, an accelerated and a decelerated flow are studied, and effects of acceleration upon the formation of a velocity profile, transition and a friction coefficient are determined for a wide range of accelerations. The results of the accelerated flow show that there are two patterns in the formation of a sectional velocity profile and transition, one of which is observed when the acceleration is relatively large compared with the propagation of viscous effects, and the other when the acceleration is comparatively small. A friction coefficient of an accelerated flow tends to be larger than that of a quasi-steady flow in the laminar region, while it has reverse tendency in the turbulent region. For a decelerated flow a turbulent region is maintained almost all over the deceleration periods, and the friction coefficient becomes larger than that of a quasi-steady flow.
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