Models of the scalar spectrum for turbulent advection

Hill, R. J.

doi:10.1017/s002211207800227x

Cited by 296 publications

(165 citation statements)

References 23 publications

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“…But an anomalous k-1 subrange is also observed experimentally for Prandtl number as low as 0.7, the atmospheric value (the "bump" , Hill 1978). Therefore, even at Pr = 1 truncation, as indicated by the scalar-derivative flatness, becomes important for R).. > 18 on a 32 3 grid.…”

Section: Jmentioning

confidence: 70%

Higher-order derivative correlations and the alignment of small-scale structures in isotropic numerical turbulence

1985

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In a three-dimensional simulation higher-order derivative correlations, including skewness and flatness (or kurtosis) factors, are calculated for velocity and passive scalar fields and are compared with structures in the flow. Up to 1283 grid points are used with periodic boundary conditions in all three directions to achieve Rλ to 82.9. The equations are forced to maintain steady-state turbulence and collect statistics. The scalar-derivative flatness is found to increase much faster with Reynolds number than the velocity-derivative flatness, and the velocity- and mixed-derivative skewnesses do not increase with Reynolds number. Separate exponents are found for the various fourth-order velocity-derivative correlations, with the vorticity-flatness exponent the largest. This does not support a major assumption of the lognormal and β models, but is consistent with some aspects of structural models of the small scales. Three-dimensional graphics show strong alignment between the vorticity, rate-of-strain, and scalar-gradient fields. The vorticity is concentrated in tubes with the scalar gradient and the largest principal rate of strain aligned perpendicular to the tubes. Velocity spectra, in Kolmogorov variables, collapse to a single curve and a short $-\frac{5}{3}$ spectral regime is observed.

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Section: Jmentioning

confidence: 70%

Higher-order derivative correlations and the alignment of small-scale structures in isotropic numerical turbulence

1985

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“…(3) Here the structure parameter C 2 n depends in general on the temperature gradient on the scales larger than L 0 . See, e.g., [22], [16] and [4] for more sophisticated models of turbulent refractive index fields.…”

Section: Introductionmentioning

confidence: 99%

White-Noise and Geometrical Optics Limits of Wigner-Moyal Equation for Wave Beams in Turbulent Media

Fannjiang

2004

Commun. Math. Phys.

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Abstract. Starting with the Wigner distribution formulation for beam wave propagation in Hölder continuous non-Gaussian random refractive index fields we show that the wave beam regime naturally leads to the white-noise scaling limit and converges to a Gaussian white-noise model which is characterized by the martingale problem associated to a stochastic differential-integral equation of the Itô type. In the simultaneous geometrical optics the convergence to the Gaussian white-noise model for the Liouville equation is also established if the ultraviolet cutoff or the Fresnel number vanishes sufficiently slowly. The advantage of the Gaussian white-noise model is that its n-point correlation functions are governed by closed form equations.

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“…to the more realistic atmospheric spectrum developed by Hill, (Hill, 1978) and defined analytically by Andrews (Andrews, 1998) …”

Section: Beam-propagation Simulationsmentioning

confidence: 99%

FY05 FM Dial Summary Report

Harper¹,

Strasburg²,

Golovich³

et al. 2005

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SummaryPacific Northwest National Laboratory's Infrared Sensors team is focused on developing methods for standoff detection of nuclear proliferation.In FY05, PNNL continued the development of the FM DIAL (frequency-modulated differential absorption LIDAR) experiment. Additional improvements to the FM DIAL trailer provided greater stability during field campaigns which made it easier to explore new locations for field campaigns. In addition to the Hanford Townsite, successful experiments were conducted at the Marine Science Laboratory in Sequim, WA and the Nevada Test Site located outside Las Vegas, NV.The range of chemicals that can be detected by FM DIAL has also increased. Prior to FY05, distributed feedback quantum cascade lasers (DFB-QCL) were used in the FM DIAL experiments. With these lasers, only simple chemicals with narrow (1-2 cm -1 ) absorption spectra, such as CO 2 and N 2 O, could be detected. Fabry-Perot (FP) QC lasers have much broader spectra (20-40 cm -1 ) which allows for the detection of larger chemicals and a wider array of chemicals that can be detected. A FP-QCL has been characterized and used during initial studies detecting DMMP (dimethyl methylphosphonate).The numerical simulations of laser propagation through the atmosphere have matured and provide good agreement between theory and experiment. An effort is underway to integrate previous IR SAGE models with the beam propagation models to provide an overall model of system performance and detection limits.The primary highlight of FY05 was our performance in the Shrike chemical release tests at the Nevada Test Site. The FM DIAL remote sensor successfully detected the release of ammonia in all of the releases that occurred during the week of July 11 th -14 th .iii

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Models of the scalar spectrum for turbulent advection

Cited by 296 publications

References 23 publications

Higher-order derivative correlations and the alignment of small-scale structures in isotropic numerical turbulence

Higher-order derivative correlations and the alignment of small-scale structures in isotropic numerical turbulence

White-Noise and Geometrical Optics Limits of Wigner-Moyal Equation for Wave Beams in Turbulent Media

FY05 FM Dial Summary Report

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