Scaling law of fine scale eddies in turbulent channel flows up to Reτ=800

Tanahashi, Mamoru; Kang, Shin-Jeong; Miyamoto, T.; Shiokawa, Showko; Miyauchi, Toshio

doi:10.1016/j.ijheatfluidflow.2004.02.016

Cited by 142 publications

(138 citation statements)

References 21 publications

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“…In fact, the intensities of the three vorticity components are roughly equal above y + « 50, and their spectra also approximately agree with each other above that level. It was shown by Tanahashi et al (2004) that the properties of the individual vortices in a turbulent channel are essentially identical to those in isotropic turbulence at similar Reynolds numbers, and the same seems to be the case in the boundary layer. The vortices in figure 11(a) resemble much more the 'tangles' described by del Alamo et al (2006) and Flores, Jiménez & del Alamo (2007), than the ordered arrays in Wu & Moin (2009), and it is especially interesting that the tallest vortical regions, which could be considered as the 'leading edges' of the diffusion of the turbulent region into the free stream, resemble much more isotropic ejections than organized hairpins.…”

Section: The Geometry Of the Vortical Structuresmentioning

confidence: 81%

“…Since the typical maximum vorticity of the compact vortices is a few times co' (Jiménez et al 1993;Tanahashi et al 2004), they are essentially decoupled from the mean velocity profile, and are approximately isotropic. In fact, the intensities of the three vorticity components are roughly equal above y + « 50, and their spectra also approximately agree with each other above that level.…”

Section: The Geometry Of the Vortical Structuresmentioning

confidence: 99%

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Turbulent boundary layers and channels at moderate Reynolds numbers

et al. 2010

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The behaviour of the velocity and pressure fluctuations in the outer layers of wall-bounded turbulent flows is analysed by comparing a new simulation of the zero-pressure-gradient boundary layer with older simulations of channels. The 99 % boundary-layer thickness is used as a reasonable analogue of the channel half-width, but the two flows are found to be too different for the analogy to be complete. In agreement with previous results, it is found that the fluctuations of the transverse velocities and of the pressure are stronger in the boundary layer, and this is traced to the pressure fluctuations induced in the outer intermittent layer by the differences between the potential and rotational flow regions. The same effect is also shown to be responsible for the stronger wake component of the mean velocity profile in external flows, whose increased energy production is the ultimate reason for the stronger fluctuations. Contrary to some previous results by our group, and by others, the streamwise velocity fluctuations are also found to be higher in boundary layers, although the effect is weaker. Within the limitations of the non-parallel nature of the boundary layer, the wall-parallel scales of all the fluctuations are similar in both the flows, suggesting that the scale-selection mechanism resides just below the intermittent region, y/S =0.3-0.5. This is also the location of the largest differences in the intensities, although the limited Reynolds number of the boundary-layer simulation (Reg «2000) prevents firm conclusions on the scaling of this location. The statistics of the new boundary layer are available from http://torroja.dmt.upm.es/ftp/blayers/.

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Section: The Geometry Of the Vortical Structuresmentioning

confidence: 81%

Section: The Geometry Of the Vortical Structuresmentioning

confidence: 99%

Turbulent boundary layers and channels at moderate Reynolds numbers

et al. 2010

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“…As in the case of Qs, vortex clusters separate into wall-attached and detached families, but, although the averaged flow field of an attached vortex cluster contains a long conical low-speed streamwise-velocity 'wake' reminiscent of streaks, headed by a shorter pair of ejections, the instantaneous shapes are irregular and very different from hairpins. The question of whether hairpin vortices persist in high-Reynolds-number wall-bounded turbulence, and of whether they should be understood as instantaneous structures (Wu & Moin 2009;Schlatter et al 2014) or as conditional statistical constructs (AJZM06; Tanahashi et al 2004;Flores & Jiménez 2006;Jiménez 2013b), remains controversial, and is the subject of much current debate.…”

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confidence: 99%

Coherent structures in statistically stationary homogeneous shear turbulence

et al. 2017

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The three-dimensional vortex clusters, and the structures based on the quadrant classification of the intense tangential Reynolds stress (Qs), are studied in direct numerical simulations of statistically stationary homogeneous shear turbulence (HST) at Taylor microscale Reynolds number Re λ ≈ 50-250, with emphasis on comparisons with turbulent channels (CHs). The Qs and vortex clusters in HST are found to be versions of the corresponding detached (in the sense of del Álamo et al. (J. Fluid Mech., vol. 561 (2006), pp. 329-358)) structures in CHs, although statistically symmetrised with respect to the substitution of sweeps by ejections and vice versa. In turn, these are more symmetric versions of the corresponding attached Qs and clusters. In both flows, only co-gradient sweeps and ejections larger than the local Corrsin scale are found to couple with the shear. They are oriented anisotropically, and are responsible for carrying most of the total Reynolds stress. Most large eddies in CHs are attached to the wall, but it is shown that this is probably a geometric consequence of their size, rather than the reason for their dynamical significance. Most small Q structures associated with different quadrants are far from each other in comparison to their size, but those that are close to each other tend to form quasi-streamwise trains of groups of a sweep and an ejection paired side by side in the spanwise direction, with a vortex cluster in between, generalising to three dimensions the corresponding arrangement of attached eddies in CHs. These pairs are organised around an inclined large-scale conditional vortex 'roller', and it is shown that the composite structure tends to be located at the interface between high-and low-velocity streaks, as well as in strong 'co-gradient' shear layers that separate streaks of either sign in which velocity is more uniform. It is further found that the conditional rollers are terminated by 'hooks' reminiscent of hairpins, both upright and inverted. The inverted hook weakens as the structures approach the wall, while the upright one changes little. At the same time, the inclination of the roller with respect to the mean velocity decreases from 45 • in HST to quasi-streamwise for † Email address for correspondence: jimenez@torroja.

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“…This is illustrated in Fig. 7 by plotting for various y + P the a priori evaluated nondimensional wall shear stress τ w , obtained from the above expressions for a plane channel flow at Re τ = 800, using the DNS data [21]. The viscous shear stress was Fig.…”

Section: Compound Wall Treatment (Cwt)mentioning

confidence: 99%

“…Right: variables normalised with u k ("*" normalisation). Symbols: DNS of Tanahashi et al [21] evaluated using τ ν w = μU P /y P , while for the turbulent one we tested two definitions. The first was obtained from the log-law expression τ t w = ρ[κU P /ln(Ey…”

Section: Compound Wall Treatment (Cwt)mentioning

confidence: 99%

Compound Wall Treatment for RANS Computation of Complex Turbulent Flows and Heat Transfer

Popovac

Hanjalić

2007

Flow Turbulence Combust

199

100

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We present a generalised treatment of the wall boundary conditions for RANS computation of turbulent flows and heat transfer. The method blends the integration up to the wall (ItW) with the generalised wall functions (GWF) that include non-equilibrium effects. Wall boundary condition can thus be defined irrespective of whether the wall-nearest grid point lies within the viscous sublayer, in the buffer zone, or in the fully turbulent region. The computations with fine and coarse meshes of a steady and pulsating flow in a plane channel, in flow behind a backwardfacing step and in a round impinging jet using the proposed compound wall treatment (CWT) are all in satisfactory agreement with the available experiments and DNS data. The method is recommended for computations of industrial flows in complex domains where it is difficult to generate a computational grid that will satisfy a priori either the ItW or WF prerequisites.Key words RANS turbulence models · wall functions · integration to the wall · compound wall treatment

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Scaling law of fine scale eddies in turbulent channel flows up to Reτ=800

Cited by 142 publications

References 21 publications

Turbulent boundary layers and channels at moderate Reynolds numbers

Turbulent boundary layers and channels at moderate Reynolds numbers

Coherent structures in statistically stationary homogeneous shear turbulence

Compound Wall Treatment for RANS Computation of Complex Turbulent Flows and Heat Transfer

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