Reynolds stress scaling in pipe flow turbulence—first results from CICLoPE

Örlü, Ramis; Fiorini, Tommaso; Segalini, Antonio; Bellani, Gabriele; Talamelli, Alessandro; Alfredsson, P. Henrik

doi:10.1098/rsta.2016.0187

Cited by 58 publications

(45 citation statements)

References 63 publications

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“…The similarity of the profiles sustains until the point FST cases peel up with the intense wall-normal fluctuations due to the presence of turbulence in the free stream. It has been shown in the literature for high Reynolds number flows that the wall-normal fluctuations exhibit a nearly constant extended plateau [22][23][24]. It is worth mentioning that the analogy of the turbulent boundary layer flows under the effect of FST with high Re flows, which is detailed in Dogan et al [5,6], is further supported here with the plateau region observed in the wall-normal variance profiles.…”

Section: A Wall-normal Velocitysupporting

confidence: 81%

Spatial characteristics of a zero-pressure-gradient turbulent boundary layer in the presence of free-stream turbulence

et al. 2019

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Particle image velocimetry (PIV) measurements are performed to examine the structural organisation inside a turbulent boundary layer under the influence of free-stream turbulence (FST). In particular, streamwise-wall-normal plane PIV measurements are presented for two cases at two different turbulent intensity levels (about 12% and 8%). The high-intensity free-stream turbulence is generated using an active grid in a wind tunnel. The statistical information of the flow regarding the wall-normal velocity and Reynolds shear stress are presented. The effect of increasing the turbulence level in the free stream for these flows has been found to have similarities with increasing Reynolds number for high Reynolds number canonical flows. Quadrant analysis is performed to determine the contributions of different Reynolds-stress-producing events. In this regard, the distribution of momentum transport events shows some similarity with channel flows, which can be justified by comparison of similar intermittency characteristics of both flows. In addition, the coherent structures found inside the boundary layer have inclined features that are consistent with the previous studies for canonical flows. The fact that the external disturbance, such as FST in this study, does not alter the organisation of the structures inside the boundary layer supports the growing evidence for a universal structure for wall-bounded flows. * jason.hearst@ntnu.no

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Section: A Wall-normal Velocitysupporting

confidence: 81%

Spatial characteristics of a zero-pressure-gradient turbulent boundary layer in the presence of free-stream turbulence

et al. 2019

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“…The choice of only some data used here does not affect the accuracy of the findings. The same conclusions apply to all the pipe-flow results of Örlü et al [47] and Furuichi et al [39], and to the boundary layer measurements of Bailey et al [43] with R τ 6000, although it is expected that difficulties will arise because of the evaluation of the mean velocity gradient for experimental data, which introduce a large scatter.…”

Section: A Logarithmic Mean Velocity Lawsupporting

confidence: 52%

Refinement of the logarithmic law of the wall

Laadhari

2019

Phys. Rev. Fluids

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Available direct numerical simulation of turbulent channel flow at moderately high Reynolds numbers data show that the logarithmic diagnostic function is a linearly decreasing function of the outer-normalized wall distance η = y/δ with a slope proportional to the von Kármán constant, κ = 0.4. The validity of this result for turbulent pipe and boundary layer flows is assessed by comparison with the mean velocity profile from experimental data. The results suggest the existence of a flow-independent logarithmic law U + = U /u τ = (1/κ) ln(y * /a), where y * = yU S /ν with U S = yS(y) being the local shear velocity and the two flow-independent constants κ = 0.4 and a = 0.36. The range of its validity extends from the inner-normalized wall distance y + = 300 up to half the outer-length scale η = 0.5 for internal flows, and η = 0.2 for zero-pressure-gradient turbulent boundary layers. Likewise, and within the same range, the mean velocity deficit follows a flow-dependent logarithmic law as a function of a local mean-shear-based coordinate. Furthermore, it is illustrated how the classical friction laws for smooth pipe and zero-pressure-gradient turbulent boundary layer are recovered from this scaling.

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“…This allows construction of a one-to-one relationship between the flow velocity and the anemometer output voltage. Although this means that calibration is not performed in a near-potential flow, the ratio u 2 /U at the centreline is sufficiently small to make insignificant differences to the potential flow calibration (Monty 2005;Örlü et al 2017). An intermediate calibration relationship between the hot-wire voltages and velocities is generated for each wall-normal point during the measurement, based on an assumption that deviations between pre-and post-calibration curves are the result of a linear drift in the hot-wire voltage with time.…”

Section: Flow Typementioning

confidence: 99%

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

et al. 2019

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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.

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Reynolds stress scaling in pipe flow turbulence—first results from CICLoPE

Abstract: One contribution of 14 to a theme issue 'Toward the development of high-fidelity models of wall turbulence at large Reynolds number' .

Cited by 58 publications

References 63 publications

Spatial characteristics of a zero-pressure-gradient turbulent boundary layer in the presence of free-stream turbulence

Spatial characteristics of a zero-pressure-gradient turbulent boundary layer in the presence of free-stream turbulence

Refinement of the logarithmic law of the wall

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

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