1988 Fiscal Year Final Research Report Summary
Experimental Study of Turbulence Structure in Pulsatile Pipe Flow
| Project/Area Number |
62550131
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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, Assistant, 工学部, 助手 (00043993)
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| Project Period (FY) |
1987 – 1988
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| Keywords | Unsteady Flow / Pulsatile Pipe Flow / Propagation of Turbulence / Ordered Motions / Reynolds Shear Stress / Relaminarization / Transient Flow / 乱流スラグ |
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| Research Abstract |
1. A couditional sampling technic based on four quadrant classification was used to clarify the turbulence structure in pulsatile pipe flows. The pulsation frequency was chosen to be about one tenth of mean burst frequency. Turbulence was generated near the wall by the same ordered motions as in a steady turbulent pipe flow. It propagated monotonically in the radial direction while decaying, but the decay rate was not affected by pulsation.
2. A time lag t exists between the fundamental components of the cross-sectional mean velocity um and the root mean square value u'rms of the axial velocity component u'. The smallest value of t was designated by tg, and tnd the radial position at which t = tg was defined as the generation position of turbulence yg. yg was well approximated by yg 20.
3. The radial propagation time of turbulence ( t- tg) was not affected by pulsation. Meanwhile, tg depended on pulsation and increased with increasing pulsation frequency. Both ( t- tg) and tg were dependent on the time-averaged Reynolds number Re ta. They decreased with increasing Re ta.
4. Near the generation position ( t- tg) is well correlated by inner variables, u^^-_*,ta and .
5. The measured values of ( t- tg) near the pipe center were well correlated by u^^-_*,ta and pipe radius R.
6. Two empirical equations for ( t- tg) were proposed.
7. Models for the Reynolds shear stress and eddy visocosity in pulsatile pipe flow were proposed.
8. Standing wave appeared when f was increased up to about 20 Hz, and relaminarization of flow occured under temporal as well as spatial accelerations. Turbulence structure in the relaminarizing process was investigated.
9. The behavior of turbulent slugs in transient pipe flow was clarified.
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