Interfaces and internal layers in a turbulent boundary layer

Eisma, Jerke; Westerweel, J.; Ooms, G.; Elsinga, Gerrit E.

doi:10.1063/1.4919909

Cited by 87 publications

(161 citation statements)

References 45 publications

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“…A spate of more recent investigations [18,19] has confirmed and further quantified the basic conception of UMZs advanced in the pioneering study by Meinhart & Adrian [17]; see figure 1a,b, which is adapted from de Silva et al [19]. These latter authors also show that the number of UMZs (and VFs) increases logarithmically with increasing Reynolds number.…”

Section: Introductionsupporting

confidence: 49%

“…The body force per unit mass f = f (y)ê x , whereê x is a unit vector in the x-direction, is included to drive the required background (laminar) shear flow that would exist in the absence of the turbulent motions. We choose a local Cartesian coordinate system moving with the presumed planar VF (a geometrical configuration perhaps more likely to be relevant to VFs in fully developed internal flows, such as plane Poiseuille flow; see Eisma et al [18]), which is taken to be coincident with the plane y = 0. The fissure, or internal shear layer, has O( ) dimensionless thickness, where (Re) → 0 as Re → ∞.…”

Section: Large Reynolds Number Analysismentioning

confidence: 99%

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A self-sustaining process model of inertial layer dynamics in high Reynolds number turbulent wall flows

Chini

Montemuro

White

et al. 2017

Phil. Trans. R. Soc. A.

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One contribution of 14 to a theme issue 'Toward the development of high-fidelity models of wall turbulence at large Reynolds number' . Field observations and laboratory experiments suggest that at high Reynolds numbers Re the outer region of turbulent boundary layers selforganizes into quasi-uniform momentum zones (UMZs) separated by internal shear layers termed 'vortical fissures' (VFs). Motivated by this emergent structure, a conceptual model is proposed with dynamical components that collectively have the potential to generate a self-sustaining interaction between a single VF and adjacent UMZs. A large-Re asymptotic analysis of the governing incompressible Navier-Stokes equation is performed to derive reduced equation sets for the streamwise-averaged and streamwise-fluctuating flow within the VF and UMZs. The simplified equations reveal the dominant physics within-and isolate possible coupling mechanisms among-these different regions of the flow.This article is part of the themed issue 'Toward the development of high-fidelity models of wall turbulence at large Reynolds number'.

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Section: Introductionsupporting

confidence: 49%

Section: Large Reynolds Number Analysismentioning

confidence: 99%

A self-sustaining process model of inertial layer dynamics in high Reynolds number turbulent wall flows

Chini

Montemuro

White

et al. 2017

Phil. Trans. R. Soc. A.

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“…For TBLs, Priyadarshana et al [51] investigated the event durations of intense vorticity using temporal data and concluded that the local Taylor time scale is a characteristic scale for these events [55]. Recently, Eisma et al [54] observed from spatial data that the thickness of internal interfaces in a TBL scales with the local Taylor microscale and equals approximately 0.4λ T . Note that this spatial interface thickness is in line with the values reported from the temporal studies [51,55], since Taylor's hypothesis is reasonably accurate in the centre of the log-region (note that orientation of the interface also plays a role in the observed thickness).…”

Section: Discussion and Conclusion (A) Near-wall Modulation Of Small mentioning

confidence: 99%

Reynolds number trend of hierarchies and scale interactions in turbulent boundary layers

Baars

Hutchins

Marušić

2017

Phil. Trans. R. Soc. A.

118

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Small-scale velocity fluctuations in turbulent boundary layers are often coupled with the larger-scale motions. Studying the nature and extent of this scale interaction allows for a statistically representative description of the small scales over a time scale of the larger, coherent scales. In this study, we consider temporal data from hot-wire anemometry at Reynolds numbers ranging from Re τ ≈2800 to 22 800, in order to reveal how the scale interaction varies with Reynolds number. Large-scale conditional views of the representative amplitude and frequency of the small-scale turbulence, relative to the large-scale features, complement the existing consensus on large-scale modulation of the small-scale dynamics in the near-wall region. Modulation is a type of scale interaction, where the amplitude of the small-scale fluctuations is continuously proportional to the near-wall footprint of the large-scale velocity fluctuations. Aside from this amplitude modulation phenomenon, we reveal the influence of the large-scale motions on the characteristic frequency of the small scales, known as frequency modulation. From the wall-normal trends in the conditional averages of the small-scale properties, it is revealed how the near-wall modulation transitions to an intermittent-type scale arrangement in the log-region. On average, the amplitude of the small-scale velocity fluctuations only deviates from its mean value in a confined temporal domain, the duration of which is fixed in terms of the local Taylor time scale. These concentrated temporal regions are centred on the internal shear layers of the large-scale uniform momentum zones, which exhibit regions of positive and negative streamwise velocity fluctuations. With an increasing scale separation at high Reynolds numbers, this interaction pattern encompasses the features found in studies on internal shear layers and concentrated vorticity fluctuations in high-Reynolds-number wall turbulence. This article is part of the themed issue ‘Toward the development of high-fidelity models of wall turbulence at large Reynolds number’.

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“…2 of Ref. [21]). We determine that the observed deviations of the wave velocities of momentum sources and sinks from the mean streamwise velocities cannot be explained as potential fluid at U ∞ contributing to the mean velocity profile.…”

Section: Resultsmentioning

confidence: 99%

“…According to this, large-scale regions of approximately uniform streamwise momentum 054601-2 are surrounded by elongated "fissures" of highly vortical flow. Later observations based on particle image velocimetry (PIV) confirmed and highlighted the importance of this interpretation [21,22].…”

Section: Introductionmentioning

confidence: 89%

Characteristics of sources and sinks of momentum in a turbulent boundary layer

Fiscaletti

Ganapathisubramani

2018

Phys. Rev. Fluids

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General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available: http://www.bristol.ac.uk/pure/about/ebr-terms In turbulent boundary layers, the wall-normal gradient of the Reynolds shear stress identifies momentum sources and sinks (T = ∂[−uv]/∂y). These motions can be physically interpreted in two ways: (1) as contributors to the turbulence term balancing the mean momentum equation, and (2) as regions of strong local interaction between velocity and vorticity fluctuations. In this paper, the space-time evolution of momentum sources and sinks is investigated in a turbulent boundary layer at the Reynolds number (Re τ ) = 2700, with time-resolved planar particle image velocimetry in a plane along the streamwise and wall-normal directions. Wave number-frequency power spectra of T fluctuations reveal that the wave velocities of momentum sources and sinks tend to match the local streamwise velocity in proximity to the wall. However, as the distance from the wall increases, the wave velocities of the T events are slightly lower than the local streamwise velocities of the flow, which is also confirmed from the tracking in time of the intense momentum sources and sinks. This evidences that momentum sources and sinks are preferentially located in low-momentum regions of the flow. The spectral content of the T fluctuations is maximum at the wall, but it decreases monotonically as the distance from the wall grows. The relative spectral contributions of the different wavelengths remains unaltered at varying wall-normal locations. From autocorrelation coefficient maps, the characteristic streamwise and wall-normal extents of the T motions are respectively 60 and 40 wall units, independent of the wall distance. Both statistics and instantaneous visualizations show that momentum sources and sinks have a preferential tendency to be organized in positive-negative pairs in the wall-normal direction.

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Interfaces and internal layers in a turbulent boundary layer

Cited by 87 publications

References 45 publications

A self-sustaining process model of inertial layer dynamics in high Reynolds number turbulent wall flows

A self-sustaining process model of inertial layer dynamics in high Reynolds number turbulent wall flows

Reynolds number trend of hierarchies and scale interactions in turbulent boundary layers

Characteristics of sources and sinks of momentum in a turbulent boundary layer

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