On the Taylor hypothesis corrections for measured energy spectra of turbulence

Gledzer, E. B.

doi:10.1016/s0167-2789(96)00300-4

Cited by 21 publications

(18 citation statements)

References 10 publications

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“…The idea is that turbulent fluctuations remain frozen while they are advected by the mean flow. In measurements of the turbulent velocity field with moderate turbulence intensity, v rms /v 0 0.1, Taylor's hypothesis works well (see Gledzer, 1997), and we have successfully used it in chapter 3. PIV measurements allow us to verify the applicability of Taylor's hypothesis to the grid-generated turbulence in our experiments.…”

Section: Taylor's Hypothesis For Free-surface Turbulencementioning

confidence: 90%

Experiments on free-surface turbulence

Savelsberg

Water

2009

J. Fluid Mech.

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We study the free surface of a turbulent flow, in particular the relation between the statistical properties of the wrinkled surface and those of the velocity field beneath it. Channel flow turbulence is generated using an active grid. Through a judicial choice of the stirring protocol the anisotropy of the subsurface turbulence can be controlled. The largest Taylor Reynolds number obtained is Reλ = 258. We characterize the homogeneity and isotropy of the flow and discuss Taylor's frozen turbulence hypothesis, which applies to the subsurface turbulence but not to the surface. The surface gradient field is measured using a novel laser-scanning device. Simultaneously, the velocity field in planes just below the surface is measured using particle image velocimetry (PIV). Several intuitively appealing relations between the surface gradient field and functionals of the subsurface velocity field are tested. For an irregular flow shed off a vertical cylinder, we find that surface indentations are strongly correlated with both vortical and strain events in the velocity field. For fully developed turbulence this correlation is dramatically reduced. This is because the large eddies of the subsurface turbulent flow excite random capillary–gravity waves that travel in all directions across the surface. Therefore, the turbulent surface has dynamics of its own. Nonetheless, it does inherit both the integral scale, which determines the predominant wavelength of the capillary–gravity surface waves, and the (an)isotropy from the subsurface turbulence. The kinematical aspects of the surface–turbulence connection are illustrated by a simple model in which the surface is described in terms of waves originating from Gaussian wave sources that are randomly sprinkled on the moving surface.

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Section: Taylor's Hypothesis For Free-surface Turbulencementioning

confidence: 90%

Experiments on free-surface turbulence

Savelsberg

Water

2009

J. Fluid Mech.

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“…A Gaussian random number generator is used, and the method is tested by checking the skewness and flatness factors of velocity gradients versus the standard Gaussian values ͑0 and 3͒. Gaussianity is attained very closely except on a 512 3 grid, where we found that ͑because of the large number of samples͒ the finite period of computerized pseudo-random number generators affects the quality of statistical sampling to a certain extent.…”

Section: Simulation and Data Analysismentioning

confidence: 99%

“…However, because of the limitations of our pseudo-random number generator ͑as stated in Sec. II͒ here we exclude the 512 3 GRF data from our analysis and instead present comparisons of data at 64 3 and 256 3 resolutions, at R respectively 38 and 141.…”

Section: Comparisons With Gaussian Random Fieldsmentioning

confidence: 99%

“…However, because of the Reynolds number limitations on previous data ͑especially earlier work 17 in DNS͒, it is important to understand in detail and quantify the Reynolds number dependence of the various statistical parameters involved. Here we draw upon a current DNS database for isotropic turbulence at ensemble-averaged Taylor-scale Reynolds numbers ranging from about 38 to 240 using up to 512 3 grid points, where some limited inertial range properties can be observed. 24 While our primary interest in this article is on local and convective contributions to the acceleration, new information is also provided on pressure gradients and viscous acceleration which were studied recently using the same database by Vedula and Yeung.…”

Section: Introductionmentioning

confidence: 99%

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Random Taylor hypothesis and the behavior of local and convective accelerations in isotropic turbulence

2001

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The properties of acceleration fluctuations in isotropic turbulence are studied in direct numerical simulations ͑DNS͒ by decomposing the acceleration as the sum of local and convective contributions ͑a L ϭ‫ץ‬u/‫ץ‬t and a C ϭu•ٌu͒, or alternatively as the sum of irrotational and solenoidal contributions ͓a I ϭϪٌ( p/) and a S ϭٌ 2 u͔. The main emphasis is on the nature of the mutual cancellation between a L and a C which must occur in order for the acceleration ͑a͒ to be small as predicted by the ''random Taylor hypothesis'' ͓Tennekes, J. Fluid Mech. 67, 561 ͑1975͔͒ of small eddies in turbulent flow being passively ''swept'' past a stationary Eulerian observer. Results at Taylor-scale Reynolds number up to 240 show that the random-Taylor scenario ͗a 2 ͘Ӷ͗a C 2 ͘ Ϸ͗a L 2 ͘, accompanied by strong antialignment between the vectors a L and a C , is indeed increasingly valid at higher Reynolds number. Mutual cancellation between a L and a C also leads to the solenoidal part of a being small compared to its irrotational part. Results for spectra in wave number space indicate that, at a given Reynolds number, the random Taylor hypothesis has greater validity at decreasing scale sizes. Finally, comparisons with DNS data in Gaussian random fields show that the mutual cancellation between a L and a C is essentially a kinematic effect, although the Reynolds number trends are made stronger by the dynamics implied in the Navier-Stokes equations.

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“…The Taylor's hypothesis is widely used in experimental turbulence studies [30], [31], [32], [33], [34], and also in ocean acoustics. The hypothesis states that if the traversing speed u of the probe is large enough, we can assume that the turbulence field is "frozen", i.e., no temporal variation occurs within the measurement duration.…”

Section: Field Is Temporally Frozenmentioning

confidence: 99%

Spectral feature classification of oceanographic processes using an autonomous underwater vehicle

Zhang¹

2000

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On the Taylor hypothesis corrections for measured energy spectra of turbulence

Cited by 21 publications

References 10 publications

Experiments on free-surface turbulence

Experiments on free-surface turbulence

Random Taylor hypothesis and the behavior of local and convective accelerations in isotropic turbulence

Spectral feature classification of oceanographic processes using an autonomous underwater vehicle

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