LDA measurements in the near-wall region of a turbulent pipe flow

Durst, F.; Jovanović, J.; Sender, Joachim

doi:10.1017/s0022112095001984

Cited by 188 publications

(114 citation statements)

References 16 publications

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“…The shaded region in (b) covers the maximum scatter of experimental boundary layers from Smith (1994), Re θ = 4600-13000, Österlund et al (2000), Re θ = 2500-27000, and de Graaff & Eaton (2000), Re θ = 1430-31000. The hatched area covers experimental pipes from Perry et al (1986), Re τ = 1600-3800, Durst et al (1995), Re τ = 271-570 and Zagarola & Smits (1997), Re τ = 1700-5.3 × 10 5 . Only y/ h < 0.1 has been included in the experimental data to avoid contamination by points in the outer layer.…”

Section: The Numerical Experimentsmentioning

confidence: 99%

Scaling of the energy spectra of turbulent channels

et al. 2004

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The spectra and correlations of the velocity fluctuations in turbulent channels, especially above the buffer layer, are analysed using new direct numerical simulations with friction Reynolds numbers up to Re$_{\tau}\,{=}\,1900$. It is found, and explained, that their scaling is anomalous in several respects, including a square-root behaviour of their width with respect to their length, and a velocity scaling of the largest modes with the centreline velocity $U_c$. It is shown that this implies a logarithmic correction to the $k^{-1}$ energy spectrum, and that it leads to a scaling of the total fluctuation intensities away from the wall which agrees well with the mixed scaling of de Graaff & Eaton (2000) at intermediate Reynolds numbers, but which tends to a pure scaling with $U_c$ at very large ones.

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Section: The Numerical Experimentsmentioning

confidence: 99%

Scaling of the energy spectra of turbulent channels

et al. 2004

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“…×, pipe, Re τ = 568 (Durst, Jovanovic & Sender 1995). Fernholz & Finley (1996) for boundary layers in the range Re τ = 900-19000.…”

Section: The Intensity Profilesmentioning

confidence: 99%

Turbulent fluctuations above the buffer layer of wall-bounded flows

2008

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The behaviour of the velocity and pressure fluctuations in the logarithmic and outer layers of turbulent flows is analysed using spectral information and probability density functions from channel simulations at Re τ 6 2000. Comparisons are made with experimental data at higher Reynolds numbers. It is found, in agreement with previous investigations, that the intensity profiles of the streamwise and spanwise velocity components have logarithmic ranges that are traced to the widening spectral range of scales as the wall is approached. The same is true for the pressure, both theoretically and observationally, but not for the normal velocity or for the tangential stress cospectrum, although even those two quantities have structures with lengths of the order of several hundred times the wall distance. Because the logarithmic range grows longer as the Reynolds number increases, variables which are 'attached' in this sense scale in the buffer layer in mixed units. These results give strong support to the attached-eddy scenario proposed by Townsend (1976), but they are not linked to any particular eddy model. The scaling of the outer modes is also examined. The intensity of the streamwise velocity at fixed y/ h increases with the Reynolds number. This is traced to the large-scale modes, and to an increased intensity of the ejections but not of the sweeps. Several differences are found between the outer structures of different flows. The outer modes of the spanwise and wall-normal velocities in boundary layers are stronger than in internal flows, and their streamwise velocities penetrate closer to the wall. As a consequence, their logarithmic layers are thinner, and some of their logarithmic slopes are different. The channel statistics are available electronically at

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“…The dimension of the measurement volume is the finite spatial resolution. The resulting measurement uncertainty is described by Durst et al in [143][144][145]. Fischer et al derived the relation between the spatial resolution, the temporal resolution and the resulting standard deviation σ v of the measured flow velocity in the measurement volume [139].…”

Section: Flow Sampling Phenomenonmentioning

confidence: 99%

Imaging Flow Velocimetry with Laser Mie Scattering

Fischer

2017

Applied Sciences

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Abstract:Imaging flow velocity measurements are essential for the investigation of unsteady complex flow phenomena, e.g., in turbomachines, injectors and combustors. The direct optical measurement on fluid molecules is possible with laser Rayleigh scattering and the Doppler effect. However, the small scattering cross-section results in a low signal to noise ratio, which hinders time-resolved measurements of the flow field. For this reason, the signal to noise ratio is increased by using laser Mie scattering on micrometer-sized particles that follow the flow with negligible slip. Finally, the ongoing development of powerful lasers and fast, sensitive cameras has boosted the performance of several imaging methods for flow velocimetry. The article describes the different flow measurement principles, as well as the fundamental physical measurement limits. Furthermore, the evolution to an imaging technique is outlined for each measurement principle by reviewing recent advances and applications. As a result, the progress, the challenges and the perspectives for high-speed imaging flow velocimetry are considered.

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LDA measurements in the near-wall region of a turbulent pipe flow

Cited by 188 publications

References 16 publications

Scaling of the energy spectra of turbulent channels

Scaling of the energy spectra of turbulent channels

Turbulent fluctuations above the buffer layer of wall-bounded flows

Imaging Flow Velocimetry with Laser Mie Scattering

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