Statistical evidence of anasymptotic geometric structure to the momentum transporting motions in turbulent boundary layers

Morrill-Winter, Caleb; Philip, Jimmy; Klewicki, Joseph

doi:10.1098/rsta.2016.0084

Cited by 8 publications

(17 citation statements)

References 26 publications

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“…These observations on wave number-frequency power spectra of the T fluctuations are consistent with the intense uv events being smaller in size and shorter in lifetime at the wall, which was postulated in the attached-eddy hypothesis in Ref. [32] and confirmed by recent hot-wire measurements [33] and time-resolved PIV data [28]. The described trend is more evident from Fig.…”

Section: Resultssupporting

confidence: 74%

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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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Section: Resultssupporting

confidence: 74%

“…This is consistent with the observations of Refs. [33] and [28]. Both experimental investigations reported a decreasing number of intense uv events when moving away from the wall, which implies that a lower number of momentum sources and sinks can also be detected for growing wall-normal locations.…”

Section: -7mentioning

confidence: 99%

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

Fiscaletti

Ganapathisubramani

2018

Phys. Rev. Fluids

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“…These cospectra quantify the energy content of the RSS, but they do not show the spectral composition of the RSS fluctuations, which are the intense quadrant events. The geometrical structure of the negative quadrant events has been recently examined in TBLs at different Reynolds numbers, for scaling purpose (Morrill-Winter et al 2017). …”

Section: Introductionmentioning

confidence: 99%

Spatial–spectral characteristics of momentum transport in a turbulent boundary layer

2017

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Spectral content and spatial organization of momentum transport events are investigated in a turbulent boundary layer at the Reynolds number (Re τ ) = 2700, with time-resolved planar particle image velocimetry. The spectral content of the Reynolds-shear-stress fluctuations reveals that the largest range of time and length scales can be observed in proximity to the wall, while this range becomes progressively more narrow when the wall distance increases. Farther from the wall, longer time and larger length scales exhibit an increasing spectral content. Wave velocities of transport events are estimated from wavenumber-frequency power spectra at different wall-normal locations. Wave velocities associated with ejection events (Q2) are lower than the local average streamwise velocity, while sweep events (Q4) are characterized by wave velocities larger than the local average velocity. These velocity deficits are almost insensitive to the wall distance, which is also confirmed from time tracking the intense transport events. The vertical advection velocities of the intense ejection and sweep events are on average a small fraction of the friction velocity U τ , different from previous observations in a channel flow. In the range of wall-normal locations 60 < y + < 600, sweeps are considerably larger than ejections, which could be because the ejections are preferentially located in between the legs of hairpin packets. Finally, it is observed that negative quadrant events of the same type tend to appear in groups over a large spatial streamwise extent.

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“…The self-similar structure they derive attains a level of consistency with attached-eddy modelling concepts [9] as well as with the structure admitted by the mean momentum equation (e.g. [10,26]). Physically, their model results show some intriguing similarities to the structure elucidated in the experiments of Baars et al [20].…”

Section: Introductionmentioning

confidence: 99%

“…For obvious reasons, this concept is attractive relative to the development of reduced models of high Reynolds number flows. The contribution by Morrill-Winter et al [10] explores evidence that the signature of this ordered structure withstands time averaging. The context for their study is established from analysis of the mean equations of motion (e.g.…”

Section: Introductionmentioning

confidence: 99%

Prospectus: towards the development of high-fidelity models of wall turbulence at large Reynolds number

Klewicki

Chini

Gibson

2017

Phil. Trans. R. Soc. A.

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Recent and on-going advances in mathematical methods and analysis techniques, coupled with the experimental and computational capacity to capture detailed flow structure at increasingly large Reynolds numbers, afford an unprecedented opportunity to develop realistic models of high Reynolds number turbulent wall-flow dynamics. A distinctive attribute of this new generation of models is their grounding in the Navier–Stokes equations. By adhering to this challenging constraint, high-fidelity models ultimately can be developed that not only predict flow properties at high Reynolds numbers, but that possess a mathematical structure that faithfully captures the underlying flow physics. These first-principles models are needed, for example, to reliably manipulate flow behaviours at extreme Reynolds numbers. This theme issue of Philosophical Transactions of the Royal Society A provides a selection of contributions from the community of researchers who are working towards the development of such models. Broadly speaking, the research topics represented herein report on dynamical structure, mechanisms and transport; scale interactions and self-similarity; model reductions that restrict nonlinear interactions; and modern asymptotic theories. In this prospectus, the challenges associated with modelling turbulent wall-flows at large Reynolds numbers are briefly outlined, and the connections between the contributing papers are highlighted. 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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Statistical evidence of anasymptotic geometric structure to the momentum transporting motions in turbulent boundary layers

Cited by 8 publications

References 26 publications

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

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

Spatial–spectral characteristics of momentum transport in a turbulent boundary layer

Prospectus: towards the development of high-fidelity models of wall turbulence at large Reynolds number

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