Journal ArticleDOI
On transition in a pipe. Part 1. The origin of puffs and slugs and the flow in a turbulent slug
Israel Wygnanski,F. H. Champagne +1 more
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In this paper, hot-wire measurements were taken in a pipe at Reynolds numbers corresponding to the onset of turbulence, where the pipe was smooth and carefully aligned so that turbulent slugs appeared naturally at Re > 5 × 104.Abstract:
Conditionally sampled hot-wire measurements were taken in a pipe at Reynolds numbers corresponding to the onset of turbulence. The pipe was smooth and carefully aligned so that turbulent slugs appeared naturally at Re > 5 × 104. Transition could be initiated at lower Re by introducing disturbances into the inlet. For smooth or only slightly disturbed inlets, transition occurs as a result of instabilities in the boundary layer long before the flow becomes fully developed in the pipe. This type of transition gives rise to turbulent slugs which occupy the entire cross-section of the pipe, and they grow in length as they proceed downstream. The leading and trailing ‘fronts’ of a turbulent slug are clearly defined. A unique relation seems to exist between the velocity of the interface and the velocity of the fluid by which relaminarization of turbulent fluid is prevented. The length of slugs is of the same order of magnitude as the length of the pipe, although the lengths of individual slugs differ at the same flow conditions. The structure of the flow in the interior of a slug is identical to that in a fully developed turbulent pipe flow. Near the interfaces, where the mean motion changes from a laminar to a turbulent state, the velocity profiles develop inflexions. The total turbulent intensity near the interfaces is very high and it may reach 15% of the velocity at the centre of the pipe. A turbulent energy balance was made for the flow near the interfaces. All of the terms contributing to the energy balance must vanish identically somewhere on the interface if that portion of the interface does not entrain non-turbulent fluid. It appears that diffusion which also includes pressure transport is the most likely mechanism by which turbulent energy can be transferred to non-turbulent fluid. The dissipation term at the interface is negligible and increases with increasing turbulent energy towards the interior of the slug.Mixed laminar and turbulent flows were observed far downstream for
\[
2000 < Re < 2700
\]
when a large disturbance was introduced into the inlet. The flow in the vicinity of the inlet, however, was turbulent at much lower Re. The turbulent regions which are convected downstream at a velocity which is slightly smaller than the average velocity in the pipe we shall henceforth call puffs. The leading front of a puff does not have a clearly defined interface and the trailing front is clearly defined only in the vicinity of the centre-line. The length and structure of the puff is independent of the character of the obstruction which created it, provided that the latter is big enough to produce turbulent flow at the inlet. The puff will be discussed in more detail later.read more
Citations
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Book ChapterDOI
Recent observations of the transition to turbulence in a pipe
Tom Mullin,Jorge Peixinho +1 more
TL;DR: In this article, the authors report the results of an experimental investigation of the transition to turbulence of Poiseuille flow in a long pipe and confirm that the recently established scaling law for the finite amplitude perturbation required to cause transition is proportional to 1/Re.
Journal ArticleDOI
Flow transitions in the surface switching of rotating fluid
Yuji Tasaka,Makoto Iima +1 more
TL;DR: In this article, the authors studied surface switching in flow driven by the constant rotation of the endwall of an open cylindrical vessel and found that the velocity fluctuations (turbulent intensity) temporally vary greatly and are strongly correlated with the surface height.
Journal ArticleDOI
Transitional flow of a non-Newtonian fluid in a pipe: Experimental evidence of weak turbulence induced by shear-thinning behavior
TL;DR: In this article, a thorough study of the flow regime where an asymmetry of the mean axial velocity profiles is observed for shear-thinning fluids flow in a pipe is presented.
Book ChapterDOI
Transition to turbulence in shear flows
TL;DR: In this paper, the authors present a typical result for a Fokker-Planck equation with non-normal relaxation matrix, showing that the non-normality of the linear operator gives rise to non-orthogonal eigenvectors and to a significant amplification of noise.
Journal ArticleDOI
Tracking stages of transition in Couette flow analytically
Michael Karp,Jacob Cohen +1 more
TL;DR: In this paper, the authors focus on a transition scenario in which the linear transient growth mechanism is initiated by four decaying normal modes and show that the four modes, the initial structure of which corresponds to counter-rotating vortex pairs, are sufficient to capture the transient growth mechanisms.
References
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Book
The Structure of Turbulent Shear Flow
TL;DR: In this paper, the authors present a method to find the optimal set of words for a given sentence in a sentence using the Bibliogr. Index Reference Record created on 2004-09-07, modified on 2016-08-08
Journal ArticleDOI
The structure of turbulent boundary layers
TL;DR: In this article, the authors describe the formation of low-speed streaks in the region very near the wall, which interact with the outer portions of the flow through a process of gradual lift-up, then sudden oscillation, bursting, and ejection.
Journal ArticleDOI
Orderly Structure in Jet Turbulence
S. C. Crow,F. H. Champagne +1 more
TL;DR: In this paper, the authors show that a large-scale orderly pattern may exist in the noiseproducing region of a round subsonic jet by observing the evolution of orderly flow with advancing Reynolds number.
Journal ArticleDOI
An Experimental Investigation of the Circumstances Which Determine Whether the Motion of Water Shall Be Direct or Sinuous, and of the Law of Resistance in Parallel Channels
TL;DR: In this article, it was shown that the general character of the motion of fluids in contact with solid surfaces depends on the relation between a physical constant of the fluid and the product of the linear dimensions of the space occupied by the fluid.
Journal ArticleDOI
The three-dimensional nature of boundary-layer instability
TL;DR: In this article, an experimental investigation is described, in which principal emphasis is given to revealing the nature of the motions in the non-linear range of boundary-layer instability and the onset of turbulence, and it is demonstrated that the actual breakdown of the wave motion into turbulence is a consequence of a new instability which arises in the aforementioned three-dimensional wave motion.