Experimental Study of Turbulent Slugs in Pulsatile Pipe Flow

脉动管流中湍流段塞的实验研究

基本信息

批准号：
60550124
负责人：
IGUCHI Manabu
金额：
$ 1.15万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1985
资助国家：
日本
起止时间：
1985 至 1986
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-60550124/
关键词：
Unsteady Flow Pulsatile Pipe Flow, Turbulent Slug Relaminarization Transition Length Turbulence Intensity Inlet Length 助走区間乱流構造

项目摘要

1. The effect of unsteadiness on turbulent slugs generated in pulsatile pipe flows was investigated. The pulsation frequencies were selected to be lower about one to two order of magnitude than the mean burst frequency. (1) Two different types of slugs were observed: one showed the same behavior as that of steady flows and the other was relaminarized. (2) The phase of the breakout of a turbulent slug depended strongly on the unsteadiness. (3) The instantaneous traveling velocities of both edges of slugs without relaminarization could be approximated by those of slugs in steady pipe flow. (4) The leading edge velocity of slugs was nearly equal to the maximum velocity of laminar fluid flow just before the leading edge. (5) The transition length depended strongly on the pulsation frequency f. It became shorter as f increased. (6) The turbulence intensity at the breakout of a slug without relaminarization had a peak at r/R <approximately equal> 0.7 <about> 0.8 in their distributions, where r the radial distance and R the pipe radius. (7) As for the laminar part of the pulsatile inlet flow of small velocity amplitude ratio, the velocity distribution could be expressed by an analytical solution based on Oseen's approximation.2. Conditional sampling was made in pulsatile pipe flow accompanied by relaminarization. Turbulent motions were classified into well-known four distinct categories. (1) The ejection and the wallward interaction played an important role when a slug broke out. (2) The contributions of sweep and outward interaction to the Reynolds shear stress snd the turbulence energy were dominant when the slug gradually ceased due to a combined effect of viscosity and acceleration. (3) After the turbulence generated near the wall reached the pipe center, the ordered motions became the same as those in steady pipe flow.3. Insight into the turbulence structure of turbulent slugs which behave like slugs in steady pipe flows must be done.

1. 研究了非定常性对脉动管流中产生的湍流段塞的影响。选择脉动频率比平均突发频率低约一到两个数量级。 (1) 观察到两种不同类型的段塞：一种表现出与稳定流相同的行为，另一种则重新层化。 (2) 湍流段塞爆发的阶段很大程度上取决于不稳定性。 (3)未经再层化的段塞两端的瞬时移动速度可近似为稳态管流中段塞的瞬时移动速度。 (4)段塞的前缘速度几乎等于前缘之前层流流体的最大速度。 (5) 过渡长度很大程度上取决于脉动频率 f。随着 f 的增加，它变得更短。 (6) 未经再层化的段塞破裂处的湍流强度在其分布中在 r/R <约等于> 0.7 <约> 0.8 处具有峰值，其中 r 为径向距离，R 为管道半径。 (7)对于小速度幅值比的脉动入口流的层流部分，其速度分布可以用基于Oseen近似的解析解来表示。2．在脉动管流中进行条件取样并伴随重新层化。湍流运动被分为众所周知的四个不同类别。 (1)弹射和向壁相互作用在弹丸爆发时发挥了重要作用。 (2)当段塞由于粘度和加速度的共同作用而逐渐停止时，扫掠和向外相互作用对雷诺剪应力和湍流能的贡献占主导地位。 (3)管壁附近产生的湍流到达管道中心后，其有序运动与稳定管流中的运动相同。3．必须深入了解湍流段塞的湍流结构，这些湍流段塞的行为类似于稳定管流中的段塞。