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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Journal ArticleDOI
Patterns in transitional shear turbulence. Part 1. Energy transfer and mean-flow interaction
TL;DR: In this paper , the physical and spectral energy balance of a turbulent-laminar pattern in plane Couette flow are computed and compared to those of uniform turbulence in wall-bounded shear flows en route to laminar flow.
Journal ArticleDOI
The critical point of the transition to turbulence in pipe flow
Vasudevan Mukund,Björn Hof +1 more
TL;DR: In this paper, the authors study the evolution of pipe flow patterns for arbitrary long times and find that after times in excess of $10^7$ advective time units, a statistical steady state is reached.
Book ChapterDOI
From localized to expanding turbulence
Bjoern Hof,A. de Lozar +1 more
TL;DR: In the transitional regime turbulence in pipe, channel and Couette flow appears in localized patches, sometimes called spots or puffs These have a fixed length and a propagation speed which depends on the Reynolds number as mentioned in this paper.
Journal ArticleDOI
Analysis of the isothermal transition process in wide aspect ratio rectangular channels
TL;DR: In this paper, the role of the inlet geometry and its impact on the transition process of a laminar gas flow to a turbulent gas flow in wide aspect ratio rectangular channels under isothermal conditions was studied.
Journal ArticleDOI
États limites et bouffées turbulentes en conduite cylindrique
TL;DR: In this article, the transition from the turbulence in conduite cylindrique to the stabilite lineaire de laminaire is observed by developpement de bouffees turbulentes, spatialement localisees.
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.