An Experimental and Numerical Study of the Small Scales of a Passive Scalar Field Generated by a Line Source in Turbulent Channel Flow PDF Download
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Author: Emmanuel Germaine
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Languages : en
Pages :
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In addition, combining the obtained results with the two approaches enable us to analyze and provide insight on the nature ofa turbulent scalar plume injected at small scales. We show that the return to isotropy of the small scales is never perfectly observed in any region of the channel for the downstream distances studied herein. However, thesmall-scale anisotropy measured in the central region is smaller than the persistent anisotropy observed in the near-wall region, which is found to be most prominent in the numerical simulations, which are performed at a lower Reynolds number than the experiments. The mean velocity gradient plays a key role in the evolution of the rate of dissipation and in this lack of isotropization of the small scales of the scalar field. " --
Author: Emmanuel Germaine
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Category :
Languages : en
Pages :
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Book Description
In addition, combining the obtained results with the two approaches enable us to analyze and provide insight on the nature ofa turbulent scalar plume injected at small scales. We show that the return to isotropy of the small scales is never perfectly observed in any region of the channel for the downstream distances studied herein. However, thesmall-scale anisotropy measured in the central region is smaller than the persistent anisotropy observed in the near-wall region, which is found to be most prominent in the numerical simulations, which are performed at a lower Reynolds number than the experiments. The mean velocity gradient plays a key role in the evolution of the rate of dissipation and in this lack of isotropization of the small scales of the scalar field. " --
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Category : Mechanics, Applied
Languages : en
Pages : 784
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Category : Aeronautics
Languages : en
Pages : 1572
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Category :
Languages : en
Pages : 18
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Category : Power resources
Languages : en
Pages : 1052
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Semiannual, with semiannual and annual indexes. References to all scientific and technical literature coming from DOE, its laboratories, energy centers, and contractors. Includes all works deriving from DOE, other related government-sponsored information, and foreign nonnuclear information. Arranged under 39 categories, e.g., Biomedical sciences, basic studies; Biomedical sciences, applied studies; Health and safety; and Fusion energy. Entry gives bibliographical information and abstract. Corporate, author, subject, report number indexes.
Author: Lakshmi P. Dasi
Publisher:
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Category : Mixing
Languages : en
Pages :
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The objective is to contribute to several issues regarding the traditional view of the local structure of passive scalar fields: (1) probability density function (PDF) of the scalar concentration and scalar gradient, (2) the scalar power spectrum, (3) the structure functions, and (4) correlation functions and multi-point correlators. In addition, the research provides a geometric description of two-dimensional transects of the passive scalar iso-surfaces using the tools of fractal geometry. The local structure is analyzed as a function of large-scale anisotropy, intermittency factor, Reynolds number, and initial condition of the scalar injection. Experiments were performed in the bed boundary layer produced by a uniform depth open channel flow of water in a tilting flume for Re [subscript lambda] = 63, 94, and 120. A small nozzle iso-kinetically delivers a passive scalar of high Schmidt number (Sc = 1000) at mid-depth to generate the turbulent scalar field. Three nozzle diameters are used to study the effects of the injection length scale. High-resolution planar laser induced fluorescence (PLIF) technique is used to measure the scalar field. The local structure far from isotropic and is influenced even at the smallest scales by large-scale anisotropy, initial injection length scale and the Reynolds number of the flow. The PDF of the scalar fluctuations is non-Gaussian and dependent on large-scale anisotropy. The PDF of scalar gradients show the influence of large-scale anisotropy on the structure at the smallest scales. The spectrum of the scalar field deviates from the k [superscript -5/3] prediction in the inertial convection regime and is dependent on large-scale anisotropy, external intermittency, and low Reynolds number. There is no evidence of Batchelors k [superscript -1] scaling law. The scaling exponents of the even-ordered structure functions appear to be inversely correlated with the kurtosis of the scalar fluctuations. The fractal geometry of the two dimensional transects of passive scalar iso-surfaces is scale dependent. The fractal dimension is 1.0 at the smallest length scale and increases in a universal manner in the viscous-convective regime. The coverage length underestimate reflects this universal behavior with practical significance. The lacunarity function shows that the instantaneous scalar field is most in-homogenous around the Kolmogorov scale.
Author: Jochen Fröhlich
Publisher: Springer
ISBN: 3319144480
Category : Technology & Engineering
Languages : en
Pages : 656
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This volume reflects the state of the art of numerical simulation of transitional and turbulent flows and provides an active forum for discussion of recent developments in simulation techniques and understanding of flow physics. Following the tradition of earlier DLES workshops, these papers address numerous theoretical and physical aspects of transitional and turbulent flows. At an applied level it contributes to the solution of problems related to energy production, transportation, magneto-hydrodynamics and the environment. A special session is devoted to quality issues of LES. The ninth Workshop on 'Direct and Large-Eddy Simulation' (DLES-9) was held in Dresden, April 3-5, 2013, organized by the Institute of Fluid Mechanics at Technische Universität Dresden. This book is of interest to scientists and engineers, both at an early level in their career and at more senior levels.
Author: Kenneth B. Southerland
Publisher:
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Category :
Languages : en
Pages : 424
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Category : Aeronautics
Languages : en
Pages : 1044
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Category : Physics
Languages : en
Pages : 1264
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