1986 Fiscal Year Final Research Report Summary
Experimental Study of Turbulent Slugs in Pulsatile Pipe Flow
| Project/Area Number |
60550124
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Fluid engineering
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| Research Institution | Osaka University |
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Principal Investigator |
IGUCHI Manabu Fac. Eng. Osaka University, 工学部, 助手 (00043993)
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| Project Period (FY) |
1985 – 1986
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| Keywords | Unsteady Flow / Pulsatile Pipe Flow, Turbulent Slug / Relaminarization / Transition Length / Turbulence Intensity / Inlet Length / 助走区間 / 乱流構造 |
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| Research Abstract |
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.
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