90°ベンド内の乱流脈動流 : 未発達の流れが流入する場合

概要

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Distributions of velocity and turbulence intensity in pulsatile flow through a circular-sectioned 90-degree bend when an undeveloped flow with a rectangular axial velocity distribution was introduced were examined experimentally. Measurements were made using a hot-wire probe at the axial Reynolds number based on time-mean velocity of 3×10^4 and the frequency parameter α(=a√<ω/ν>, a : internal radius of pipe, ω : angular frequency, ν : kinematic viscosity of fluid) of 28.0 and 72.3 for a bend whose radius of the centerline curvature is 5.0 times the pipe radius. At α=28.0, axial velocities and turbulence intensities vary in time proportionally to the instantaneous volumetric flow rate. On the other hand, at α=72.3, the axial velocity profile shows a configuration differing from that of quasi-steady flow at each phase angle near the inner wall. With cyclic changes of the velocity profile, the turbulence intensities near the inner wall are also subject to a large change during one cycle, that is, they decrease during the accelerating period and increase in the decelerating one. However, they were found to exhibit only a slight change near the outer wall.
一般社団法人日本機械学会の論文
1995-05-25