The Experts below are selected from a list of 186 Experts worldwide ranked by ideXlab platform
Howard C. Rodean - One of the best experts on this subject based on the ideXlab platform.
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Stochastic Lagrangian Models of Turbulent Diffusion - Stochastic Lagrangian Models of Turbulent Diffusion
Meteorological Monographs, 1996Co-Authors: Howard C. RodeanAbstract:This monograph is intended to give atmospheric scientists a basic understanding of the physical and mathematical foundations of stochastic Lagrangian models of Turbulent Diffusion.
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stochastic lagrangian models of Turbulent Diffusion
Meteorological Monographs, 1996Co-Authors: Howard C. RodeanAbstract:This monograph is intended to give atmospheric scientists a basic understanding of the physical and mathematical foundations of stochastic Lagrangian models of Turbulent Diffusion.
Kazutomo Ohtake - One of the best experts on this subject based on the ideXlab platform.
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Experimental Study of Turbulent Diffusion Flame Structure and Its Similarity
Jsme International Journal Series B-fluids and Thermal Engineering, 1997Co-Authors: Kazutomo OhtakeAbstract:The interaction between reaction and Turbulent mixing strongly affects the structures of a Turbulent Diffusion flame, the characteristics of which are greatly affected by the combination of working conditions such as burner exit configurations, burner size, fuel and oxidant. This study discusses in detail the Turbulent Diffusion flame structure and its similarity using a laboratory-scale Turbulent Diffusion flame measured by laser Rayleigh scattering. It also discusses the factors affecting the similarity in flame structure and the Turbulent Diffusion flame length determined using its Turbulent power spectral density. The -5/3 power law holds in the fuel jet and combustion regions but in the air entrainment regions, the -5/3 and -1 power laws coexist, and which shows that both Turbulent and molecular thermal Diffusions become important. The constancy of the Turbulent Diffusion flame length at a high Reynolds number is discussed with respects to the characteristics of flame structure.
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An Experimental Study of Space and Time-Resolved Structures of Turbulent Diffusion Flame
Jsme International Journal Series B-fluids and Thermal Engineering, 1996Co-Authors: Kazutomo OhtakeAbstract:The authors discuss in detail the various heat transportation mechanisms existing in Turbulent Diffusion flames by use of spectral analyses. Space and time-resolved structures of Turbulent Diffusion flames were analyzed by two-point laser Rayleigh spectroscopy (LRS) which did not directly interfere with the combustion media during measurement. The Turbulent Diffusion flame structures were divided into 4 regions based on the characteristics of their spectral analysis of time-dependent temperature signals. In order to discuss the macroscopic heat transportation mechanism, the coherent function from cross and power spectral functions at Region I∼IV was analyzed. From these analyses, the following Diffusion characteristics at each region were revealed. Region I : three-dimensional Diffusion mechanism (x-, r-, z-axes), Region II : one-dimensional Diffusion mechanism (z-axis), Region III : two-dimensional Diffusion mechanism (x-, z-axes), Region IV : no specific Diffusion mechanism.
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Microscopic Structures in Turbulent Diffusion Flames
Jsme International Journal Series B-fluids and Thermal Engineering, 1994Co-Authors: Kazutomo OhtakeAbstract:Microscopic structures in Turbulent Diffusion flames are studied by time-resolved temperature distributions measured by a laser-sheet-illuminated Rayleigh scattering (LRS) method recorded by a high-speed VTR system, and one-point LRS measurement. The microscopic structures of temperature distribution are measured by analyzing the two-dimensional LRS pictures by image processing. Coaxial Turbulent Diffusion flames at moderate Reynolds numbers, which exhibit typical Diffusion flame structures, are formed on laboratory-scale burners. It is found that the flame can be divided into four characteristic regions based on the distributions of macroscale temperature fluctuations. These four regions are visualized by the two-dimensional LRS images. The Turbulent heat-transfer mechanisms in these four regions are discussed in terms of the two-dimensional LRS and the power spectral density of temperature fluctuations measured by one-point LRS. Clusters of temperature inhomogeneity are observed by the image analyses in Regions I and III. It is found that different structures of microscopic temperature inhomogeneity exist within Taylor's dissipation length scale defined by velocity fluctuations.
Peter R Kramer - One of the best experts on this subject based on the ideXlab platform.
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simplified models for Turbulent Diffusion theory numerical modelling and physical phenomena
Physics Reports, 1999Co-Authors: Andrew J Majda, Peter R KramerAbstract:Abstract Several simple mathematical models for the Turbulent Diffusion of a passive scalar field are developed here with an emphasis on the symbiotic interaction between rigorous mathematical theory (including exact solutions), physical intuition, and numerical simulations. The homogenization theory for periodic velocity fields and random velocity fields with short-range correlations is presented and utilized to examine subtle ways in which the flow geometry can influence the large-scale effective scalar diffusivity. Various forms of anomalous Diffusion are then illustrated in some exactly solvable random velocity field models with long-range correlations similar to those present in fully developed turbulence. Here both random shear layer models with special geometry but general correlation structure as well as isotropic rapidly decorrelating models are emphasized. Some of the issues studied in detail in these models are superdiffusive and subdiffusive transport, pair dispersion, fractal dimensions of scalar interfaces, spectral scaling regimes, small-scale and large-scale scalar intermittency, and qualitative behavior over finite time intervals. Finally, it is demonstrated how exactly solvable models can be applied to test and design numerical simulation strategies and theoretical closure approximations for Turbulent Diffusion.
Joseph Katz - One of the best experts on this subject based on the ideXlab platform.
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experimental investigation of Turbulent Diffusion of slightly buoyant droplets in locally isotropic turbulence
Physics of Fluids, 2008Co-Authors: Balaji Gopalan, Edwin Malkiel, Joseph KatzAbstract:High-speed inline digital holographic cinematography is used for studying Turbulent Diffusion of slightly buoyant 0.5–1.2 mm diameter diesel droplets and 50 μm diameter neutral density particles. Experiments are performed in a 50×50×70 mm3 sample volume in a controlled, nearly isotropic turbulence facility, which is characterized by two dimensional particle image velocimetry. An automated tracking program has been used for measuring velocity time history of more than 17 000 droplets and 15 000 particles. For most of the present conditions, rms values of horizontal droplet velocity exceed those of the fluid. The rms values of droplet vertical velocity are higher than those of the fluid only for the highest turbulence level. The Turbulent Diffusion coefficient is calculated by integration of the ensemble-averaged Lagrangian velocity autocovariance. Trends of the asymptotic droplet Diffusion coefficient are examined by noting that it can be viewed as a product of a mean square velocity and a Diffusion time s...
Rixin Yu - One of the best experts on this subject based on the ideXlab platform.
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Turbulent Diffusion of chemically reacting flows theory and numerical simulations
Physical Review E, 2017Co-Authors: T Elperin, N Kleeorin, M A Liberman, Andrei Lipatnikov, I Rogachevskii, Rixin YuAbstract:The theory of Turbulent Diffusion of chemically reacting gaseous admixtures developed previously [T. Elperin, Phys. Rev. E 90, 053001 (2014)PLEEE81539-375510.1103/PhysRevE.90.053001] is generalized for large yet finite Reynolds numbers and the dependence of Turbulent Diffusion coefficient on two parameters, the Reynolds number and Damkohler number (which characterizes a ratio of Turbulent and reaction time scales), is obtained. Three-dimensional direct numerical simulations (DNSs) of a finite-thickness reaction wave for the first-order chemical reactions propagating in forced, homogeneous, isotropic, and incompressible turbulence are performed to validate the theoretically predicted effect of chemical reactions on Turbulent Diffusion. It is shown that the obtained DNS results are in good agreement with the developed theory. (Less)
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Turbulent Diffusion of chemically reacting flows theory and numerical simulations
arXiv: Fluid Dynamics, 2016Co-Authors: T Elperin, N Kleeorin, M A Liberman, Andrei Lipatnikov, I Rogachevskii, Rixin YuAbstract:The theory of Turbulent Diffusion of chemically reacting gaseous admixtures developed previously (Phys. Rev. E {\bf 90}, 053001, 2014) was generalized for large yet finite Reynolds numbers, and the dependence of Turbulent Diffusion coefficient versus two parameters, the Reynolds number and Damk\"ohler number (which characterizes a ratio of Turbulent and reaction time scales) was obtained. Three-dimensional direct numerical simulations (DNS) of a finite thickness reaction wave for the first-order chemical reactions propagating in forced, homogeneous, isotropic, and incompressible turbulence were performed to validate the theoretically predicted effect of chemical reactions on Turbulent Diffusion. We found that the obtained DNS results are in a good agreement with the developed theory. In line with theoretical predictions, the DNS data show a significant decrease in the Turbulent Diffusion coefficient with the increasing Damk\"ohler number.
