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- Author or Editor: F. N. Frenkiel x
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Abstract
Some elements of the statistical theory of turbulence are briefly reviewed from the viewpoint of their application to micrometeorology.Several relations concerning turbulent diffusion in a field of homogeneous and isotropic turbulence are then discussed. The mean-concentration distributions for an instantaneous and for a continuous point-source are investigated, with particular attention to the case when the intensity of turbulence cannot be considered as small in comparison with the mean velocity. The time history of mean-concentration distributions in a diffusing spherical cloud is then studied.
The relation between Fick's differential equation of diffusion and the statistical theory of turbulence is studied, and the limits of validity of Fick's equation are determined. Finally, the relation between the coefficient of eddy diffusion and the statistical characteristics of turbulence is discussed.
Abstract
Some elements of the statistical theory of turbulence are briefly reviewed from the viewpoint of their application to micrometeorology.Several relations concerning turbulent diffusion in a field of homogeneous and isotropic turbulence are then discussed. The mean-concentration distributions for an instantaneous and for a continuous point-source are investigated, with particular attention to the case when the intensity of turbulence cannot be considered as small in comparison with the mean velocity. The time history of mean-concentration distributions in a diffusing spherical cloud is then studied.
The relation between Fick's differential equation of diffusion and the statistical theory of turbulence is studied, and the limits of validity of Fick's equation are determined. Finally, the relation between the coefficient of eddy diffusion and the statistical characteristics of turbulence is discussed.
Abstract
A conventional anemometer used in the atmosphere or in a wind tunnel measures velocities projected on a plane independently of their directions in the plane. The relation between the frequency distribution of those velocities and the frequency distribution of the turbulent components parallel to the direction of the mean velocity is discussed. At small intensities of the longitudinal turbulence the two distributions are approximately the same. However, at intensities of turbulence of the order of those measured in the atmosphere, the difference between the two frequency distributions becomes appreciable.
Some experimental frequency distributions of wind velocities are presented, and the intensities of atmospheric turbulence are determined from the experiments.
Abstract
A conventional anemometer used in the atmosphere or in a wind tunnel measures velocities projected on a plane independently of their directions in the plane. The relation between the frequency distribution of those velocities and the frequency distribution of the turbulent components parallel to the direction of the mean velocity is discussed. At small intensities of the longitudinal turbulence the two distributions are approximately the same. However, at intensities of turbulence of the order of those measured in the atmosphere, the difference between the two frequency distributions becomes appreciable.
Some experimental frequency distributions of wind velocities are presented, and the intensities of atmospheric turbulence are determined from the experiments.
Abstract
The dispersion of smoke puffs has been used as a method of measuring turbulent diffusion in the atmosphere. Some of the basic equations of turbulent diffusion as applied to the dispersion of small-scale smoke puff and are recalled. The intensity of turbulence in the lower atmosphere is then determined from the experimental measurements. The experimental measurements are analyzed to find the characteristics of turbulence as observed on a small scale. Comparsion is made with order smoke-puff and soap-bubble diffusion studies.
Abstract
The dispersion of smoke puffs has been used as a method of measuring turbulent diffusion in the atmosphere. Some of the basic equations of turbulent diffusion as applied to the dispersion of small-scale smoke puff and are recalled. The intensity of turbulence in the lower atmosphere is then determined from the experimental measurements. The experimental measurements are analyzed to find the characteristics of turbulence as observed on a small scale. Comparsion is made with order smoke-puff and soap-bubble diffusion studies.
Abstract
Turbulent diffusion from an infinite line source in a homogeneous, stationary, non-isotropic turbulent flow is studied. Spatial mean-concentration distributions are determined as functions of the statistical characteristics of turbulence. Particular attention is given to the evaluation of mean concentrations at relatively small distances from the source both upstream and downstream. At high intensities of turbulence, the resulting mean-concentration values may differ considerably from those obtained when the turbulent diffusion in the wind direction is neglected.
Abstract
Turbulent diffusion from an infinite line source in a homogeneous, stationary, non-isotropic turbulent flow is studied. Spatial mean-concentration distributions are determined as functions of the statistical characteristics of turbulence. Particular attention is given to the evaluation of mean concentrations at relatively small distances from the source both upstream and downstream. At high intensities of turbulence, the resulting mean-concentration values may differ considerably from those obtained when the turbulent diffusion in the wind direction is neglected.
