Spatial resolution correction for wall-bounded turbulence measurements

Smits, Alexander J.; Monty, Jason; Hultmark, Marcus; Bailey, Sean; Hutchins, Nicholas; Marušić, Ivan

doi:10.1017/jfm.2011.19

Cited by 103 publications

(61 citation statements)

References 31 publications

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“…The pipe data are plotted for y + > 10 at the lowest three Re τ (Re τ 5400) but only for y + > 300 at higher Re τ in order to stay clear of spatial resolution issues (cf. Smits et al 2011). In general, very good agreement is observed between the two geometries even at 10th order with possibly a slight trend of increasing E * p,1 with increasing Re τ in the pipe.…”

Section: Universality Of the Ratiosmentioning

confidence: 59%

Statistics of turbulence in the energy-containing range of Taylor–Couette compared to canonical wall-bounded flows

Krug¹,

Yang²,

Silva³

et al. 2017

J. Fluid Mech.

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Considering structure functions of the streamwise velocity component in a framework akin to the extended self-similarity hypothesis (ESS), de Silva et al. (J. Fluid Mech., vol. 823,2017, pp. 498-510) observed that remarkably the large-scale (energy-containing range) statistics in canonical wall bounded flows exhibit universal behaviour. In the present study, we extend this universality, which was seen to encompass also flows at moderate Reynolds number, to Taylor-Couette flow. In doing so, we find that also the transversal structure function of the spanwise velocity component exhibits the same universal behaviour across all flow types considered. We further demonstrate that these observations are consistent with predictions developed based on an attached-eddy hypothesis. These considerations also yield a possible explanation for the efficacy of the ESS framework by showing that it relaxes the self-similarity assumption for the attached eddy contributions. By taking the effect of streamwise alignment into account, the attached eddy model predicts different behaviour for structure functions in the streamwise and in the spanwise directions and that this effect cancels in the ESS-framework -both consistent with the data. Moreover, it is demonstrated here that also the additive constants, which were previously believed to be flow dependent, are indeed universal at least in turbulent boundary layers and pipe flow where high-Reynolds number data are currently available.

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Section: Universality Of the Ratiosmentioning

confidence: 59%

Statistics of turbulence in the energy-containing range of Taylor–Couette compared to canonical wall-bounded flows

Krug¹,

Yang²,

Silva³

et al. 2017

J. Fluid Mech.

View full text Add to dashboard Cite

show abstract

“…In real flows, modes associated with the near-wall cycle (λ + x ≈ 10 3 , c + ≈ 10-12) are known to be the most energetic at low Reynolds number (Monty et al 2009;Smits et al 2011). So, the energy content predicted by a broadband forcing assumption does not exactly match the energy content in real flows.…”

Section: Effect Of Opposition Control In Spectral Spacementioning

confidence: 98%

“…Of course, these results must be interpreted with some caution since the broadband forcing assumption employed here does not accurately capture the uncontrolled energy spectrum in the real flow. However, it is generally true that longer faster-moving modes become more energetic at higher Reynolds number (Smits et al 2011). …”

Section: Effect Of Opposition Control In Spectral Spacementioning

confidence: 99%

Opposition control within the resolvent analysis framework

2014

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as an example. Under this formulation, the velocity field for turbulent pipe flow is decomposed into a series of highly amplified (rank-1) response modes, identified from a gain analysis of the Fourier-transformed NavierStokes equations. These rank-1 velocity responses represent propagating structures of given streamwise/spanwise wavelength and temporal frequency, whose wall-normal footprint depends on the phase speed of the mode. Opposition control, introduced via the boundary condition on wall-normal velocity, affects the amplification characteristics (and wall-normal structure) of these response modes; a decrease in gain indicates mode suppression, which leads to a decrease in the drag contribution from that mode. With basic assumptions, this rank-1 model reproduces trends observed in previous direct numerical simulation and large eddy simulation, without requiring high-performance computing facilities. Further, a wavenumber-frequency breakdown of control explains the deterioration of opposition control performance with increasing sensor elevation and Reynolds number. It is shown that slower-moving modes localized near the wall (i.e. attached modes) are suppressed by opposition control. Faster-moving detached modes, which are more energetic at higher Reynolds number and more likely to be detected by sensors far from the wall, are further amplified. These faster-moving modes require a phase lag between sensor and actuator velocity for suppression. Thus, the effectiveness of opposition control is determined by a trade-off between the modes detected by the sensor. However, it may be possible to develop control strategies optimized for individual modes. A brief exploration of such mode-optimized control suggests the potential for significant performance improvement.

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“…Although the streamwise variance profile exhibits a mild second peak, the fact that the wire length in inner units L + increases up to 40 and 80 viscous units for the boundary-layer and Dantec probes, respectively, excludes the possibility of drawing any firm conclusions regarding this. By utilizing the spatial resolution correction outlined in [28], it was found that the entire range covered by the X-wire measurements is virtually free of spatial resolution effects. The near-wall data from the single wires, on the other hand, are affected and the results from the correction scheme are shown in figure 5a as grey symbols.…”

Section: Reynolds Stresses (A) Streamwise Componentmentioning

confidence: 99%