A flow-visualization study of transition in plane Poiseuille flow

Carlson, Dale R.; Widnall, Sheila E.; Peeters, M. F.

doi:10.1017/s0022112082002006

Cited by 239 publications

(207 citation statements)

References 27 publications

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“…Alavyoon et al 7 performed visualization of a turbulent spot and they could not generate a turbulent spot below Re = 1470. They also confirmed the oblique waves and the spot splitting, though the front and rear propagation velocities were higher than estimations by Carlson et al 6 These experiments on transitional channel flow indicate that the marginal Re is in the vicinity of 1400, except in the experiment by Badri Narayanan. Numerical studies are consistent with this value, such as that by Orszag and Kells, 8 who performed direct numerical simulations (DNS) for strongly disturbed channel flow.…”

Section: Introductionsupporting

confidence: 63%

“…The equivalent length scale to this peak frequency is 80 d* which is much larger than typical scales of the turbulent disturbance. Considering the facts that the low-frequency peak is mainly observed in the transitional flow, and that the scale is equivalent to the turbulent patch interval observed in the flow visualization, 6,10,11 it appears that this low-frequency peak is the result of turbulent patch passing.…”

Section: Relaminarizing Channel Flowmentioning

confidence: 90%

“…Below this Re they observed only low-frequency fluctuation far downstream from the disturbance source. Carlson et al 6 investigated natural and artificial turbulent spots in the range of a transitional Re with flake particle flow visualization and found that the spot could be generated by an artificial disturbance at or above Re of about 1330. They observed strong oblique waves at the sides and the rear of turbulent spots, and spots splitting into two spots downstream, with their gap filled with longitudinal structures.…”

Section: Introductionmentioning

confidence: 99%

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Experimental investigation of relaminarizing and transitional channel flows

Seki

Matsubara

2012

Physics of Fluids

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A hot-wire measurement was conducted in a planar channel flow that originated from a strongly disturbed flow in an entrance channel followed by an expansion channel used to reduce the Reynolds number (Re). From ceasing decrease of the streamwise velocity fluctuation energy and the linear extrapolation of the intermittency factor, the lower marginal Re, which is defined as the minimum Re for partial existence of sustainable turbulence, is estimated around 1400 based on the channel width and the bulk velocity. The upper marginal Re at which the intermittency factor reaches one is about 2600. The flow fields passing a turbulent patch were reconstructed with conditional sampling of the streamwise velocity data based on the time of laminarturbulence interfaces and the reconstructed flow fields indicate a large-scale flow structure across laminar and turbulent parts. This large structure makes it possible for some regions to be at higher Re than the average, so that turbulence can partly survive. The moderate-scale disturbances larger than the turbulent one appear in the non-turbulent parts of the transitional flow, and in these cases the non-turbulent velocity profile is almost identical to the turbulent one. The large-scale fluctuation is observed even over Re = 2600. This leads to the conclusion that a turbulent channel flow close to the upper marginal Re becomes inhomogeneous. C 2012 American Institute of Physics. [http://dx

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Section: Introductionsupporting

confidence: 63%

Section: Relaminarizing Channel Flowmentioning

confidence: 90%

Section: Introductionmentioning

confidence: 99%

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Experimental investigation of relaminarizing and transitional channel flows

Seki

Matsubara

2012

Physics of Fluids

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“…30 In channel flow, the ECS arise at ReϷ 650; 26 experimentally, the transition to turbulence is at ReϷ 1000. 31 For pipe flow ReϷ 1300 (Ref. 28) for the appearance of the ECS and ReϷ 2100 (Ref.…”

Section: Introductionmentioning

confidence: 99%

Polymer drag reduction in exact coherent structures of plane shear flow

et al. 2004

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Recently discovered traveling-wave solutions to the Navier-Stokes equations in plane shear geometries provide model flows for the study of turbulent drag reduction by polymer additives. These solutions, or "exact coherent states" (ECS), qualitatively capture the dominant structure of the near-wall buffer region of shear turbulence, i.e., counter-rotating pairs of streamwise-aligned vortices flanking a low-speed streak in the streamwise velocity. The optimum length scales for the ECS match well the length scales of the turbulent coherent structures and evidence suggests that the ECS underlie the dynamics of these structures. We study here the effect of viscoelasticity on these states. The changes to the velocity field for the viscoelastic ECS, where the FENE-P model calculates the polymer stress, mirror the modifications seen in experiments of fully turbulent flows of polymer solutions at low to moderate levels of drag reduction: drag is reduced, streamwise velocity fluctuations increase while wall-normal fluctuations decrease, and smaller wavelength structures are suppressed. These modifications to the ECS are due to the suppression of the streamwise vortices. The polymer molecules become highly stretched in the wavy, streamwise streaks, where the flow is predominately elongational, then relax as they move from the streaks into and around the streamwise vortices, where the flow is predominately rotational. This relaxation of the polymer molecules produces a force that directly opposes the fluid motion in the vortices, weakening them. Since the pressure fluctuations have their greatest magnitude (i.e., they are most negative) in the cores of the vortices, a reduction in vortex strength leads to a decrease in the magnitude of the pressure fluctuations. The pressure fluctuations redistribute energy from the streamwise velocity fluctuations to the Reynolds shear stress, so a decrease in their magnitude leads to a reduction in turbulent drag. For the viscoelastic ECS, we also find that after the onset of drag reduction (at Weissenberg number, WeϷ 7) there is a dramatic increase in the critical wall-normal length scale at which the ECS can exist. This sharp increase in length scale mirrors experimental observations and is also consistent with the observed shift to higher Reynolds numbers of the transition to turbulence in polymer solutions.

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“…[9][10][11][12] The Reynolds number is defined as Re = U c h/ν, where U c is the centerline velocity of the base flow, h is the half channel height, and ν is the kinematic viscosity of the fluid. Later studies focused on higher Reynolds number flows (Re ≥ 1000): turbulent spots and their characteristics have been thoroughly studied [13][14][15][16][17] and, more recently, numerical simulations revealed the presence of closely arranged turbulent bands or stripes.…”

mentioning

confidence: 99%

Turbulent bands in plane-Poiseuille flow at moderate Reynolds numbers

et al. 2015

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In this letter, we show via numerical simulations that the typical flow structures appearing in transitional channel flows at moderate Reynolds numbers are not spots but isolated turbulent bands, which have much longer lifetimes than the spots. Localized perturbations can evolve into isolated turbulent bands by continuously growing obliquely when the Reynolds number is larger than 660. However, interactions with other bands and local perturbations cause band breaking and decay. The competition between the band extension and breaking does not lead to a sustained turbulence until Re becomes larger than about 1000. Above this critical value, the bands split, providing an effective mechanism for turbulence spreading.

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A flow-visualization study of transition in plane Poiseuille flow

Cited by 239 publications

References 27 publications

Experimental investigation of relaminarizing and transitional channel flows

Experimental investigation of relaminarizing and transitional channel flows

Polymer drag reduction in exact coherent structures of plane shear flow

Turbulent bands in plane-Poiseuille flow at moderate Reynolds numbers

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