まっすぐな円管内の乱流旋回流の特性 : 弱い旋回流入時の流れおよび角運動量の変化(流体工学,流体機械)

概要

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Althought it is well-known that the swirl strength of a turbulent swirling flow in a straight pipe decays downstream and eventually becomes a non swirling pipe flow, few studies on the flow change in a weak swirling flow have been reported. In this study, changes in the flow pattern and the angular momentum in a weak swirling flow are described. Experiments are performed at a Reynolds number of Re=10^5, which is based on the pipe inner diameter and the axial mean velocity under the condition that a guide-vane swirl generator, in which the guide vane angle is set at 5 degrees, is employed. As a result, it is confirmed that the combined vortex formed upstream in a straight pipe changes into a forced vortex far downstream. Both the swirl number and the swirling angle at r/R=0.95, which are employed to define the swirl strength, exponentially decrease downstream. Also, the radial distribution and contours of the local angular momentum, which do not change in the entrance region, change considerably in the annular region far downstream.
2008-12-25