Experimental measurement of large-scale three-dimensional structures in a turbulent boundary layer. Part 1. Vortex packets

Dennis, David; Nickels, T. B.

doi:10.1017/s0022112010006324

Cited by 173 publications

(160 citation statements)

References 25 publications

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“…These features are found on either side, but again due to their weak correlation with the spanwise swirling event they appear first on one side in the present iso-surface display. The horns have also been observed by Dennis & Nickels (2011). From the conditional eddy we take again the distribution of the spanwise swirling strength magnitude and use that for the template (figure 1b).…”

Section: Vortex Detection and Tracking Methodsmentioning

confidence: 99%

Tracking of vortices in a turbulent boundary layer

et al. 2012

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The motion of spanwise vortical elements and large-scale bulges has been tracked in the outer region between wall-normal distance z/δ = 0.11 and 0.30 of a turbulent boundary layer at Re θ = 2460. The experimental dataset of time-resolved threedimensional velocity fields used has been obtained by tomographic particle image velocimetry. The tracking of these structures yields their respective average trajectories as well as the variations thereof, quantified by the root mean square of the trajectory coordinates as a function of time. It is demonstrated that the variation in convection can be described by a dispersion model for infinitesimal particles in homogeneous turbulence, which suggests that these vortical structures and bulges are transported passively by the external velocity field without significant changes in their topology, at least over the present observation time of 1.2δ/U e . However, this does not mean that the structure's convection velocity is equal to the local flow velocity at each instant. Differences of the order of the Kolmogorov or wall friction velocity have been observed for the spanwise vortical elements. In addition, the simultaneous detection and tracking of multiple structures allows an evaluation of the relative velocity between two spanwise vortex elements, which are approximately aligned along the streamwise direction. The typical streamwise distance between such neighbouring structures is found to be around 0.2δ. Their relative velocities are small, especially the streamwise component, which shows less variation as may be expected based on the relative flow velocity statistics for the same separation distance. This appears consistent with the hairpin packet model, which comprises a set of streamwise aligned hairpins travelling coherently. In exceptional cases, however, the structures approach each other rapidly, forcing an interaction on a time scale of the order of 1δ/U e . It is shown that the measured variation in convection velocity can further be used successfully to predict the temporal development of space-time correlation functions starting from the instantaneous correlation map. In this prediction the structures are assumed to convect without change, following our observations.

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Section: Vortex Detection and Tracking Methodsmentioning

confidence: 99%

Tracking of vortices in a turbulent boundary layer

et al. 2012

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“…For instance, Dennis and Nickels 44 average conditional on a swirl criterion to identify hairpin vortices, yielding the scale distribution in K and y associated with the structure. In contrast, we work in the opposite direction: specifying K and yielding the wall-normal distribution of the velocity of the response modes, which we associate with coherent structure.…”

Section: Reproduction and Extension Of Statistical And Structuramentioning

confidence: 99%

Experimental manipulation of wall turbulence: A systems approach

2013

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We review recent progress, based on the approach introduced by McKeon and Sharma [J. Fluid Mech. 658, 336-382 (2010)], in understanding and controlling wall turbulence. The origins of this analysis partly lie in nonlinear robust control theory, but a differentiating feature is the connection with, and prediction of, state-of-the-art understanding of velocity statistics and coherent structures observed in real, high Reynolds number flows. A key component of this line of work is an experimental demonstration of the excitation of velocity response modes predicted by the theory using non-ideal, but practical, actuation at the wall. Limitations of the approach and promising directions for future development are outlined. C 2013 American Institute of Physics. [http://dx

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“…High-negative u regions are indicated by dark grey, while light grey shade denotes highly positive u regions. Bottom panel shows the Biot Savart law calculations for an idealized packet of hairpin vortices with their image vortices in the wall, as per the schematic of Adrian et al (2000) shown on the left side instantaneous measurements from Hutchins and Marusic (2007a) and Dennis and Nickels (2011a) are shown in Fig. 5.…”

Section: Large-scale Motions and Very Large-scale Superstructuresmentioning

confidence: 99%

Coherent structures in flow over hydraulic engineering surfaces

Adrian

Marušić

2012

Journal of Hydraulic Research

117

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Wall-bounded turbulence manifests itself in a broad range of applications, not least in hydraulic systems. Here, we briefly review the significant advances over the past few decades in the fundamental study of wall turbulence over smooth and rough surfaces, with an emphasis on coherent structures and their role at high Reynolds numbers. We attempt to relate these findings to parallel efforts in the hydraulic engineering community and discuss the implications of coherent structures in important hydraulic phenomena.

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Experimental measurement of large-scale three-dimensional structures in a turbulent boundary layer. Part 1. Vortex packets

Cited by 173 publications

References 25 publications

Tracking of vortices in a turbulent boundary layer

Tracking of vortices in a turbulent boundary layer

Experimental manipulation of wall turbulence: A systems approach

Coherent structures in flow over hydraulic engineering surfaces

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