Showing papers on "Schmidt number published in 1979"
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TL;DR: In this article, the relationship between the turbulent Prandtl and Schmidt number is investigated and the results are based on modeled transport equations for the turbulent kinetic energy, the turbulent heat flux, and the turbulent mass flux.
124 citations
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TL;DR: In this article, a chemically reacting, turbulent shear layer between two streams was investigated in a new, blowdown water tunnel, which contained dilute, aqueous solutions of diffusion-limited reactants (phenolphthalein and sodium hydroxide) which mixed in the layer and reacted to form a visible reaction product.
Abstract: A chemically reacting, turbulent shear layer between two streams was investigated in a new, blowdown water tunnel. The two streams contained dilute, aqueous solutions of diffusion-limited reactants (phenolphthalein and sodium hydroxide, respectively) which mixed in the layer and reacted to form a visible reaction product. Using optical densitometry techniques, the amount of product was measured as a function of Reynolds number. These results for water (Schmidt No. = 600) are compared with the previous mixing measurements of Konrad in a gaseous shear layer (Sc = 0.7) and the simple mixing method of Broadwell. The unique flow visualization provided by the visible reaction product revealed a remarkable spanwise instability (superimposed on the large coherent vortices) which appears to be important in introducing three-dimensional motions into the flow.
94 citations
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TL;DR: In this article, an electrochemical analogue technique has been used to measure the mass-heat transfer distribution in pipes roughened with square small ribs, and it has been found that the mass transfer distributions are less non-uniform at higher Reynolds numbers and that they are virtually independent of the Schmidt number over a wide range of Sc.
66 citations
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TL;DR: An exact analysis of the effects of mass transfer and free convection currents on MHD Stokes' (Rayleigh's) problem for the flow of an electrically conducting, incompressible, viscous fluid past an impulsively started vertical plate, under the action of a transversely applied magnetic field is made in this article.
66 citations
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TL;DR: In this article, the gradient transfer theory for turbulent diffusion is reformulated in order to obtain an improved method for applied dispersion studies, and the diffusion equation is written in terms of the turbulent diffusivity transfer function.
Abstract: The gradient transfer theory for turbulent diffusion is reformulated in order to obtain an improved method for applied dispersion studies. The basic innovation is that diffusivity of single Fourier components of the concentration field is treated separately, i.e., spectral turbulent diffusivity coefficients are introduced. The value of the diffusivity decreases with increasing wave vector k of the concentration spectrum. The rate of growth of an expanding cloud of material thus becomes dependent on the stage of growth. This is in qualitative agreement with the statistical dispersion theory. It is shown that the assumption of k-dependent diffusivity leads to a nonlocal flux-gradient relation. A new function, the turbulent diffusivity transfer function, is introduced. The turbulent diffusive flux depends on concentration gradients at all points in the space. The diffusion equation is written in terms of the turbulent diffusivity transfer function. The width of the turbulent diffusivity transfer fun...
47 citations
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TL;DR: In this paper, an engineering analysis for an electrolytic reactor incorporating a stacked net electrode in which the electrolyte flow is in longitudinal direction and the current flow in the normal direction is carried out.
46 citations
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TL;DR: In this article, local mass transfer coefficients resulting from the impingement of a two-dimensional laminar air jet on a flat surface have been measured using a holographic technique.
27 citations
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TL;DR: An exact analysis of the mass transfer effects on the free convection flow of an incompressible viscous fluid past an impulsively started infinite vertical (wall) limiting surface (Stokes's or Rayleigh's problem) has been carried out as discussed by the authors.
Abstract: An exact analysis of the mass transfer effects on the free convection flow of an incompressible viscous fluid past an impulsively started infinite vertical (wall) limiting surface (Stokes's or Rayleigh's problem) has been carried out. Expressions for the velocity, temperature, species concentration and skin friction are obtained by using the Laplace transform technique. The velocity field and the skin friction are shown graphically for air (P=0.71) and mercury (P=0.025). The effects ofG (Grashof number),Gc (the modified Grashof number) andSc (Schmidt number) are considered qualitatively during the course of discussion.
16 citations
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TL;DR: In this paper, the authors examined the variation of the mass transfer rate along a small amplitude wavy surface which is exchanging mass with a turbulently flowing fluid and showed that a soluble flat surface is unstable in the presence of a turbulent flow.
Abstract: In a previous paper, we have examined the variation of the mass transfer rate along a small amplitude wavy surface which is exchanging mass with a turbulently flowing fluid. We now use these results to show that a soluble flat surface is unstable in the presence of a turbulent flow. The wavelength of the most rapidly growing surface disturbance, made dimensionless with respect to the friction velocity and the kinematic viscosity, is found to be a very weak function of the Schmidt number. These results provide a possible explanation for wavelike dissolution patterns observed in caves and on the underside of river ice. The analysis predicts that deposition patterns should be quite different from dissolution patterns in that the most rapidly growing wave for deposition has a length of zero.
14 citations
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TL;DR: In this paper, the authors considered the transfer of mass or heat between a fluid and a small amplitude solid wavy surface and found that a periodic variation of the transfer rate can occur because of wave induced variations of the normal convective flow and of the properties of the turbulence.
Abstract: This paper considers the transfer of mass or heat between a fluid and a small amplitude solid wavy surface. A periodic variation of the transfer rate can occur because of wave induced variations of the normal convective flow and of the properties of the turbulence. Solutions of the mass balance equations are presented for the laminar flow at a large Schmidt number or Prandtl number and for turbulent flow at large and small wave numbers. For turbulent flows at intermediate wave numbers, the prediction is limited by inadequacies of present theories that model the wave induced variation in the turbulent diffusion of heat or mass. In order to provide guidance for this modeling, new measurements on the variation of the mass transfer rate along a solid wavy surface are presented for a Schmidt number of 729. An analogy between momentum and mass transfer is explored as a means for evaluating the turbulent diffusion terms.
The amplitude of the function describing the mass transfer variation is found to decrease with decreasing wave number and the phase to increase with decreasing wave number. The phase angle and the amplitude of the variation in the mass transfer rate relative to the average mass transfer rate are insensitive to changes in Schmidt number or Prandtl number. For turbulent flows, the phase change can be large enough that the maximum in the mass transfer rate can exist somewhere in the trough of the wave. This result is of considerable significance in interpreting wavelike dissolution patterns.
14 citations
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TL;DR: In this paper, the effects of both crystal and crucible rotation are included in a model of crystal growth from the melt, which is developed in terms of a small parameter based upon the Schmidt number.
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TL;DR: In this paper, mass-discrimination effects in stagnation-point ion extraction are treated for a plasma with a wide range of Knudsen number, i.e., when the charged particle's mean free path ⩽ the sampling electrode radius.
19 Jul 1979
TL;DR: In this paper, a model for the calculation of turbulent flows was constructed which incorporates effects of Reynolds stress relaxation with the generation or destruction of turbulent energy by rotation, and the model was verified by comparison with experiment.
Abstract: : The more important results and developments achieved as a direct result of this contract are as follows: A model for the calculation of turbulent flows was constructed which incorporates effects of Reynolds stress relaxation with the generation or destruction of turbulent energy by rotation. The model was verified by comparison with experiment. It was then used to predict the properties of isolated turbulent vortices and applied to the turbulent mixing layer, in particular to the formation and interaction of the organized structure in the mixing layer. An alternative approach to the mixing layer in which it is modelled by a rolling-up vortex sheet between fluids of different density has also been formulated. Calculations of strained flame elements for use in the coherent flame mode of H2, F combustion showed that only at very high strain rates was sufficient vibrational nonequilibrium produced to be of interest for a chemical laser. This result is reflected in the fact that only in the early portion of the jet, where strain rates are a maximum, does this vibrational nonequilibrium occur. Experimental results were obtained in a new facility and by a new technique for the amount of reaction product obtained betwen two chemically reacting aqueous streams. Results at high and low Reynolds number showed the dependence of the mixing on Reynolds number and Schmidt number. A transition Reynolds number region was found and the nature of the generation of small scale motions which dominate the formation of reaction product was explored. (Author)
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TL;DR: In this article, an analysis of the mass transfer effects on the hydromagnetic free convective flow of an electrically conducting, incompressible viscous fluid, past an infinite, nonconducting, porous, vertical wall with constant suction, has been carried out, in presence of a transverse magnetic field.
Abstract: An analysis of the mass transfer effects on the hydromagnetic free — convective flow of an electrically conducting, incompressible viscous fluid, past an infinite, non-conducting, porous, vertical wall with constant suction, has been carried out, in presence of a transverse magnetic field. The induced magnetic field is taken into consideration and the terms representing the viscous dissipative heat and the Joule heating are included in the energy equation. Approximate solutions to coupled non-linear equations governing the flow are obtained, when the magnetic Prandtl number is unity and the magnetic parameterM < 1. Expressions are given for the velocity, the induced magnetic field, the temperature, the skin friction, the electric current density and the rate of heat transfer in terms of the Nusselt number. The variations of the above quantities are presented graphically, and the paper is concluded with a quantitative discussion.
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01 Jan 1979
TL;DR: In this paper, the process of evaporation of a surface liquid drop in a uniform air stream has been studied and considered as being a diffusion plus momentum controlled phenomenon and the important parameters governing this phenomenon are the Stanton number, the drop Reynolds number, and the Schmidt number.
Abstract: The process of evaporation of a surface liquid drop in a uniform air stream has been studied and considered as being a diffusion plus momentum controlled phenomenon. The important parameters governing this phenomenon are the Stanton number, the drop Reynolds number, and the Schmidt number. Experiments have been conducted on the evaporation of water drops from a smooth plane surface in the presence and absence of a uniform air stream. The Reynolds numbers calculated from the equivalent initial dropdiameter varied from 4500 to 22000. Results of real size - time measurements indicate that the evaporation history is characterized by a decreasing pattern, but with an upward convex form. The overall evaporation time of a liquid drop in still air could be several time higher than that resulting when even a relatively low velocity air stream is employed.