Showing papers on "Schmidt number published in 1969"
TL;DR: In this article, the authors derived the velocity profile and radial eddy diffusivities of mass and momentum from a two-part model based on a sublayer profile and the Von Karman similarity hypothesis.
Abstract: Solutions of the diffusion equation are obtained for mass transfer in a fully developed turbulent flow in a plain circular tube in two axisymmetric situations. The cases studied are a point source positioned at the centre of the tube and a ring source in the tube wall in which there is a uniform mass flux along a short length of the tube. The purpose of the work is to establish the correctness of the descriptions of the velocity profile and radial eddy diffusivities of mass and momentum in order to provide a firm base from which consideration of the non-axisymmetric situation could proceed.The turbulent velocity profile is deduced from a two-part model based on a sublayer profile and the Von Karman similarity hypothesis. The radial eddy diffusivity of momentum is described by an expression due to Reichardt and Van Driest and from this the radial eddy diffusivity of mass as a function of radius is obtained by use of a ratio which takes account of fluid properties and the value of the radial eddy diffusivity.The analysis is substantiated by experiments carried out with nitrous oxide, Schmidt number = 0·77, for Reynolds numbers from 20,000 to 130,000. The concentration profiles measured at several axial positions downstream from the source are in good agreement with the analytical solutions in both cases. Direct measurements of the eddy diffusivity of mass and momentum were obtained as added confirmation and also gave good agreement with the theory.
23 citations
TL;DR: Turbulent Schmidt number as function of ratio between turbulent and molecular kinematic viscosities for He, carbon dioxide and normal octane eddy diffusivities as discussed by the authors.
15 citations
TL;DR: In this article, it was shown that the mass and momentum transfer rates measured as described in Part I do not exhibit the expected analogue relationship, changing with the flow variables in quite different ways.
13 citations
TL;DR: In this paper, the Schmidt number and the ratio of the boundary layer thickness to the wire radius were used to measure average mass transfer coefficients between a stagnant liquid and a moving continuous cylinder.
10 citations
TL;DR: In this paper, the effective turbulent dispersion coefficient was analyzed and the ratio of the eddy momentum and mass diffusivity coefficients determined for reported measurements in circular pipes and open channels.
Abstract: The effective turbulent dispersion coefficient is analyzed, and the ratio of the eddy momentum and mass diffusivity coefficients determined for reported measurements in circular pipes and open channels. Its dependence to the ratio between the linearized Stokesian response time of the particle and the turbulent time macroscale is suggested.
8 citations
TL;DR: In this paper, mass transfer coefficients were obtained from weight loss measurements of benzoic acid life saver elements of various diameters and lengths, which were assembled as an integral part of the inner core of the annulus and maintained by a tensioning device.
Abstract: Entrance region and fully developed mass transfer from the inner core of annuli was investigated for a fully developed velocity profile and a Schmidt number of 760 Constant wall concentration was the satisfied boundary condition of the inner core
The ranges of parameters investigated were 21,400 to 75,600 for Reynolds number, 0164 to 0741 for the annulus diameter ratio, and 0018 to 385 for the length to hydraulic diameter ratios
Experiments were performed in an open water flow loop Mass transfer coefficients were obtained from weight loss measurements of benzoic acid life saver elements of various diameters and lengths These elements were assembled as an integral part of the inner core of the annulus Concentricity was maintained by a tensioning device
The local Sherwood number is found to be significantly affected by the annulus diameter ratio, Reynolds number, and the length to hydraulic diameter ratio A correlation is developed which predicts 93% of the data used for its development to within ± 10%
3 citations
TL;DR: In this article, the dimensionless dispersion coefficient for a pollutant ejected into a uniform turbulent flow is shown to depend on the characteristics of the viscous sublayers; calculations are carried out to demonstrate this dependence.
Abstract: The dimensionless dispersion coefficient for a pollutant ejected into a uniform turbulent flow is shown to depend on the characteristics of the viscous sublayers; calculations are carried out to demonstrate this dependence. The results have shown that the dimensionless dispersion coefficient increases quite substantially for turbulent pipe flow at low Reynolds number and high Schmidt number. The increased dispersion coefficient is due to the fact that extremely small diffusivity occurs in the viscous sublayer.
2 citations