Smooth- and rough-wall boundary layer structure from high spatial range particle image velocimetry

Squire, Dougal T.; Morrill-Winter, Caleb; Hutchins, Nicholas; Marušić, Ivan; Schultz, Michael P.; Klewicki, Joseph

doi:10.1103/physrevfluids.1.064402

Cited by 14 publications

(24 citation statements)

References 74 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Unfortunately, the present PIV measurements are incapable of resolving either of the regions described above, due to their limited streamwise extent and to laser reflection issues near to the wall (see Squire et al 2016b). This is demonstrated by the dashed box in figure 1(a), which shows the range of wall-normal locations and streamwise scales fully resolved by the PIV measurements.…”

Section: Spectra Of Streamwise Velocity Fluctuationsmentioning

confidence: 88%

“…Note that T = TU ∞ /δ × 10 −3 , where T is the sampling time. T14, MW16 and S16b are abbreviations for Talluru et al (2014a), Morrill-Winter et al (2016) and Squire et al (2016b), respectively.…”

Section: Methodsmentioning

confidence: 99%

“…For the latter, a stationary Pitot-static pair located in the free stream constituted the calibration standard. The PIV measurements employed here are described and validated in de Silva et al 2014and Squire et al (2016b), respectively, for the smooth and rough walls. All PIV data were obtained using an array of eight 14-bit PCO 4000 PIV cameras (CCD sensor:…”

Section: Methodsmentioning

confidence: 99%

“…There is significantly less justification for the application of the frozen turbulence hypothesis in flows above perturbed walls, where the turbulence intensities as a proportion of the local mean can be significantly higher. Squire et al (2016b), for example, demonstrate that under identical wind tunnel operating conditions, roughening the bounding wall with sandpaper can cause a percentage increase in u 2 /U relative to the smooth wall of approximately 40 %, and that this percentage increase grows with roughness Reynolds number. Presuming then that u 2 /U provides a crude indication of the amplitude of temporal fluctuations in the convecting frame, it seems inevitable that the frozen turbulence assumption will become decreasingly accurate as roughness Reynolds number is increased, with an increasing proportion of the total energy in the temporal framework being aliased to erroneous wavelengths.…”

Section: Introductionmentioning

confidence: 96%

See 3 more Smart Citations

Applicability of Taylor’s hypothesis in rough- and smooth-wall boundary layers

et al. 2016

Self Cite

View full text Add to dashboard Cite

The spatial structure of smooth- and rough-wall boundary layers is examined spectrally at approximately matched friction Reynolds number ($\unicode[STIX]{x1D6FF}^{+}\approx 12\,000$). For each wall condition, temporal and true spatial descriptions of the same flow are available from hot-wire anemometry and high-spatial-range particle image velocimetry, respectively. The results show that over the resolved flow domain, which is limited to a streamwise length of twice the boundary layer thickness, true spatial spectra of smooth-wall streamwise and wall-normal velocity fluctuations agree, to within experimental uncertainty, with those obtained from time series using Taylor’s frozen turbulence hypothesis (Proc. R. Soc. Lond. A, vol. 164, 1938, pp. 476–490). The same applies for the streamwise velocity spectra on rough walls. For the wall-normal velocity spectra, however, clear differences are observed between the true spatial and temporally convected spectra. For the rough-wall spectra, a correction is derived to enable accurate prediction of wall-normal velocity length scales from measurements of their time scales, and the implications of this correction are considered. Potential violations to Taylor’s hypothesis in flows above perturbed walls may help to explain conflicting conclusions in the literature regarding the effect of near-wall modifications on outer-region flow. In this regard, all true spatial and corrected spectra presented here indicate structural similarity in the outer region of smooth- and rough-wall flows, providing evidence for Townsend’s wall-similarity hypothesis (The Structure of Turbulent Shear Flow, vol. 1, 1956).

show abstract

Section: Spectra Of Streamwise Velocity Fluctuationsmentioning

confidence: 88%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

See 2 more Smart Citations

Applicability of Taylor’s hypothesis in rough- and smooth-wall boundary layers

et al. 2016

Self Cite

View full text Add to dashboard Cite

show abstract

“…2011; Vallikivi, Ganapathisubramani & Smits 2015; Squire et al. 2016). Further investigations revealed that the VLSM carry more than 50 % of the turbulent kinetic energy (TKE) (Balakumar & Adrian 2007) and have a significant amplitude modulation effect on the small-scale motions near the wall (Hutchins & Marusic 2007 b ; Mathis et al.…”

Section: Introductionmentioning

confidence: 99%

Experimental study on the effects of particle–wall interactions on VLSM in sand-laden flows

2021

View full text Add to dashboard Cite

show abstract

Large coherence of spanwise velocity in turbulent boundary layers

et al. 2018

View full text Add to dashboard Cite

The spatial signature of spanwise velocity coherence in turbulent boundary layers has been studied using a series of unique large-field-of-view multicamera particle image velocimetry experiments, which were configured to capture streamwise/spanwise slices of the boundary layer in both the logarithmic and the wake regions. The friction Reynolds number of $Re_{\unicode[STIX]{x1D70F}}\approx 2600$ was chosen to nominally match the simulation of Sillero et al. (Phys. Fluids, vol. 26 (10), 2014, 105109), who had previously reported oblique features of the spanwise coherence at the top edge of the boundary layer based on the sign of the spanwise velocity, and here we find consistent observations from experiments. In this work, we show that these oblique features in the spanwise coherence relate to the intermittent turbulent bulges at the edge of the layer, and thus the geometry of the turbulent/non-turbulent interface, with the clear appearance of two counter-oriented oblique features. Further, these features are shown to be also present in the logarithmic region once the velocity fields are deconstructed based on the sign of both the spanwise and the streamwise velocity, suggesting that the often-reported meandering of the streamwise-velocity coherence in the logarithmic region is associated with a more obvious diagonal pattern in the spanwise velocity coherence. Moreover, even though a purely visual inspection of the obliqueness in the spanwise coherence may suggest that it extends over a very large spatial extent (beyond many boundary layer thicknesses), through a conditional analysis, we show that this coherence is limited to distances nominally less than two boundary layer thicknesses. Interpretation of these findings is aided by employing synthetic velocity fields of a boundary layer constructed using the attached eddy model, where the range of eddy sizes can be prescribed. Comparisons between the model, which employs an array of self-similar packet-like eddies that are randomly distributed over the plane of the wall, and the experimental velocity fields reveal a good degree of agreement, with both exhibiting oblique features in the spanwise coherence over comparable spatial extents. These findings suggest that the oblique features in the spanwise coherence are likely to be associated with similar structures to those used in the model, providing one possible underpinning structural composition that leads to this behaviour. Further, these features appear to be limited in spatial extent to only the order of the large-scale motions in the flow.

show abstract

Smooth- and rough-wall boundary layer structure from high spatial range particle image velocimetry

Cited by 14 publications

References 74 publications

Applicability of Taylor’s hypothesis in rough- and smooth-wall boundary layers

Applicability of Taylor’s hypothesis in rough- and smooth-wall boundary layers

Experimental study on the effects of particle–wall interactions on VLSM in sand-laden flows

Large coherence of spanwise velocity in turbulent boundary layers

Contact Info

Product

Resources

About