On the correlation between enstrophy and energy dissipation rate in a turbulent wake

Zhu, Yonggang; Antonia, R. A.

doi:10.1007/bf02506068

Cited by 19 publications

(20 citation statements)

References 37 publications

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“…Power spectral densities [44] and spectra of vorticity fluctuations [45] have been measured in wind tunnels. Informative spatial vorticity contours have been obtained from direct numerical simulations [46].…”

Section: Origins Of the Hot Spotsmentioning

confidence: 99%

Engine hot spots: Modes of auto-ignition and reaction propagation

Bates

Bradley

Paczko

et al. 2016

Combustion and Flame

114

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expresses the influences of hot spot temperature gradient and fuel characteristics, and a unique value of it might serve as a boundary between auto-ignitive and deflagrative regimes. Other combustion regimes can also be identified, including a mixed regime of both auto-ignitive and "normal" 2 deflagrative burning. The paper explores the performances of a number of different engines in the regimes of controlled auto-ignition, normal combustion, combustion with mild knock and, ultimately, super-knock. The possible origins of hot spots are discussed and it is shown that the dissipation of turbulent energy alone is unlikely to lead directly to sufficiently energetic hot pots. The knocking characterisation of fuels also is discussed.

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Section: Origins Of the Hot Spotsmentioning

confidence: 99%

Engine hot spots: Modes of auto-ignition and reaction propagation

Bates

Bradley

Paczko

et al. 2016

Combustion and Flame

114

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show abstract

“…While these structures are strong on their centerlines, they become weaker off centerline (Finnigan and Shaw 2000). The relation between the dissipation rate and the vorticity has been documented in Zhu and Antonia (1997), Nelkin (1999), and Zeff et al (2003). To the best of our knowledge, it has not been studied in the atmosphere.…”

Section: E the Relation Between The Dissipation Rate And The Out-of-mentioning

confidence: 99%

PIV Measurements in the Atmospheric Boundary Layer within and above a Mature Corn Canopy. Part I: Statistics and Energy Flux

Hout¹,

Wei²,

Luznik³

et al. 2007

J. Atmos. Sci.

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Particle image velocimetry (PIV) measurements just within and above a mature corn canopy have been performed to clarify the small-scale spatial structure of the turbulence. The smallest resolved scales are about 15 times the Kolmogorov length scale ( Ϸ 0.4 mm), the Taylor microscales are about 100, and the Taylor scale Reynolds numbers range between R ϭ 2000 and 3000. The vertical profiles of mean flow and turbulence parameters match those found in previous studies. Frequency spectra, obtained using the data as time series, are combined with instantaneous spatial spectra to resolve more than five orders of magnitude of length scales. They display an inertial range spanning three decades. However, the small-scale turbulence in the dissipation range exhibits anisotropy at all measurement heights, in spite of apparent agreement with conditions for reaching local isotropy, following a high-Reynolds-number wind tunnel study. Directly calculated subgrid-scale (SGS) energy flux, determined by spatially filtering the PIV data, increases significantly with decreasing filter size, providing support for the existence of a spectral shortcut that bypasses the cascading process and injects energy directly into small scales. The highest measured SGS flux is about 40% of the estimated energy cascading rate as determined from a Ϫ5/3 fit to the spectra. Terms appearing in the turbulent kinetic energy budget that can be calculated from the PIV data are in agreement with previous results. Evidence of a very strong correlation between dissipation rate and out-of-plane component of the vorticity is demonstrated by a striking similarity between their time series.

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“…This relation has been justified in low Reynolds number, Re = 1530, flows in lab experiments [4]. Our measurements were taken in the field flow with Red > 2 x 10 7 , given u.> 1 ms -', d= 30m, and v =1.4 x 10 m 2 s7l.…”

Section: Statistics Of Enstrophy and Turbulence Kinetic Energy Dissipmentioning

confidence: 79%

“…The turbulence intermittency is estimated using the autocorrelation function of the The black curve is the empirical curve [4]. The variable a represents demeaned I/2, Ihl, Il, and II1, and ar, represents its standard deviation.…”

Section: Discussionmentioning

confidence: 99%