On the use of the Reynolds decomposition in the intermittent region of turbulent boundary layers

Kwon, Yongseok; Hutchins, Nicholas; Monty, Jason

doi:10.1017/jfm.2016.161

Cited by 27 publications

(17 citation statements)

References 17 publications

(23 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Moreover, the applicability of the model is demonstrated for the canonical wall-bounded flows considered here, namely the zero-pressure gradient boundary layer, pipe, and channel flows, and the results are seen to be consistent with known trends for the wake strength between these flows. Finally, we note that our results for internal geometries, where no TNTI is present, are in line with recent findings on internal shear layers in these geometries reported by Kwon et al (2014) and Kwon et al (2016).…”

Section: Discussionsupporting

confidence: 93%

“…Even though the overall agreement of the model with the data is very good, a slight but consistent difference is observed between the model prediction and the data for 0.5 < z/δ < 0.8 in the TBL. As Kwon et al (2016) (see also Kwon 2016) have shown, TNTI oscillations 'contaminate' the fluctuating field in the outer region of wall-bounded flows. By comparing to an alternative decomposition based on averages conditioned on the TNTI position, they demonstrated that the classical Reynolds decomposition leads to slightly higher fluctuation levels where the flow is intermittent.…”

Section: Mean Velocitymentioning

confidence: 94%

See 1 more Smart Citation

Revisiting the law of the wake in wall turbulence

2016

View full text Add to dashboard Cite

The streamwise mean velocity profile in a turbulent boundary layer is classically described as the sum of a log law extending all the way to the edge of the boundary layer and a wake function. While there is theoretical support for the log law, the wake function, defined as the deviation of the measured velocity profile from the log law, is essentially an empirical fit and has no real physical underpinning. Here, we present a new physically motivated formulation of the velocity profile in the outer region, and hence for the wake function. In our approach, the entire flow is represented by a two-state model consisting of an inertial self-similar region designated as ‘pure wall flow state’ (featuring a log-law velocity distribution) and a free stream state, which results in a jump in velocity at the interface separating the two. We show that the model provides excellent agreement with the available high Reynolds number mean velocity profiles if this interface is assumed to fluctuate randomly about a mean position with a Gaussian distribution. The new concept can also be extended to internal geometries in the same form, again confirmed by the data. Furthermore, adopting the same interface distribution in a two-state model for the streamwise turbulent intensities, with unchanged parameters, also yields a reliable and consistent prediction for the decline in the outer region of these profiles in all geometries considered. Finally, we discuss differences between our model interface and the turbulent/non-turbulent interface (TNTI) in turbulent boundary layers. We physically interpret the two-state model as lumping the effects of internal shear layers and the TNTI into a single discontinuity at the interface.

show abstract

Section: Discussionsupporting

confidence: 93%

Section: Mean Velocitymentioning

confidence: 94%

Revisiting the law of the wake in wall turbulence

2016

View full text Add to dashboard Cite

show abstract

“…We define the streamwise velocity fluctuations , where is the streamwise velocity, and the overbar denotes the ensemble average. For the TBL, the streamwise fluctuating component is decomposed by considering the local height of the turbulent/non-turbulent interface (Kwon, Hutchins & Monty 2016); that is, , where is the conditional mean velocity as a function of and . The profile of shows a significant discrepancy compared with that of in the intermittent region, whereas they collapse close to the wall (Kwon et al.…”

Section: Dns Data and Cluster Identification Methodsmentioning

confidence: 99%

Statistical behaviour of self-similar structures in canonical wall turbulence

2020

View full text Add to dashboard Cite

show abstract

“…Another potential source of difference between the internal and external flows in figure 9(a,b), may be due to use of Reynolds decomposition in obtaining the u fluctuations. While this is a standard practice, if multiple states with different mean exist in a flow (such as turbulent and nonturbulent regions), all states are reduced to a single common mean (Kwon et al 2016). Hence, the use of Reynolds decomposition can exacerbate observed differences between internal and external flows under outer scaling, as demonstrated by Kwon (2016), who improved the collapse of the two-point correlation of a boundary layer and a channel using an alternate decomposition that separated the turbulent and quiescent core/non-turbulent regions.…”

Section: Comparisons Between Pipe and Boundary Layer Flowsmentioning

confidence: 99%

Simultaneous skin friction and velocity measurements in high Reynolds number pipe and boundary layer flows

et al. 2019

Self Cite

View full text Add to dashboard Cite

Streamwise velocity and wall-shear stress are acquired simultaneously with a hot-wire and an array of azimuthal/spanwise-spaced skin friction sensors in large-scale pipe and boundary layer flow facilities at high Reynolds numbers. These allow for a correlation analysis on a per-scale basis between the velocity and reference skin friction signals to reveal which velocity-based turbulent motions are stochastically coherent with turbulent skin friction. In the logarithmic region, the wall-attached structures in both the pipe and boundary layers show evidence of self-similarity, and the range of scales over which the self-similarity is observed decreases with an increasing azimuthal/spanwise offset between the velocity and the reference skin friction signals. The present empirical observations support the existence of a self-similar range of wall-attached turbulence, which in turn are used to extend the model of Baars et al. (J. Fluid Mech., vol. 823, p. R2) to include the azimuthal/spanwise trends. Furthermore, the region where the self-similarity is observed correspond with the wall height where the mean momentum equation formally admits a self-similar invariant form, and simultaneously where the mean and variance profiles of the streamwise velocity exhibit logarithmic dependence. The experimental observations suggest that the self-similar wall-attached structures follow an aspect ratio of $7:1:1$ in the streamwise, spanwise and wall-normal directions, respectively.

show abstract

On the use of the Reynolds decomposition in the intermittent region of turbulent boundary layers

Cited by 27 publications

References 17 publications

Revisiting the law of the wake in wall turbulence

Revisiting the law of the wake in wall turbulence

Statistical behaviour of self-similar structures in canonical wall turbulence

Simultaneous skin friction and velocity measurements in high Reynolds number pipe and boundary layer flows

Contact Info

Product

Resources

About