Showing papers on "Schmidt number published in 1982"
TL;DR: In this article, mass transfer in a turbulent pipe flow is studied and the effect of flow obstacles, such as orifices and circumferential slots with varying diameter and axial length, is studied.
Abstract: Electrochemical measurements of mass transfer in a turbulent pipe flow are presented. In particular the effect of flow obstacles, such as orifices and circumferential slots with varying diameter and axial length, has been studied. The results also include measurements of mass transfer downstream, a sudden expansion or reduction of the tube diameter. The experiments were performed at a Schmidt number of 1460 and Reynolds numbers ranging between and . The work presented in this paper is a part of a project aiming to study the relation between corrosion and mass transfer at high flow rates with particular emphasis on disturbed turbulent pipe flow.
91 citations
TL;DR: In this article, an exact solution of the flow of an incompressible viscous fluid past an infinite vertical plate uniformly accelerated in the vertical direction is presented, where the presence of foreign mass is also taken into account.
43 citations
TL;DR: In this article, the velocity-gradient disturbances are not due to the usual interaction of Reynolds stress with the shear stress of the mean flow, but are due to interaction with the surface pressure fluctuations converted from the velocity fluctuations of the oncoming jet.
Abstract: Local measurement of the mass-transfer rate and velocity gradient when an axisymmetric jet impinges on a flat plate was carried out using an electrochemical technique. Local measurement of the surface pressure on the flat plate was carried out separately using piezoelectric pressure transducers. The stagnation-point mass-transfer coefficient reaches a maximum when the flat plate is placed at 6 nozzle diameters from a convergent nozzle. It has been confirmed that the mass transfer to the flat plate for a high Schmidt number is greatly enhanced owing to the velocity-gradient disturbances in the wall region of the boundary layer, while the momentum transfer is insensitive to such disturbances. The relative intensity of the velocity-gradient fluctuations on the wall has an extremely large value at and near to the stagnation point, and decreases downstream, approaching a large constant value.These velocity-gradient disturbances are not due to the usual interaction of Reynolds stress with the shear stress of the mean flow, but are due to the interaction with the surface-pressure fluctuations converted from the velocity fluctuations of the oncoming jet.The three co-ordinate dimensions of large-scale eddies are calculated from the auto- and spatial correlations of the surface-pressure fluctuations. It is considered that such large-scale eddies play an important role in the production of a velocity-gradient disturbance in the wall region of the boundary layer from the velocity turbulence of the approaching jet.
40 citations
TL;DR: In this paper, the interaction between turbulent diffusion, Brownian diffusion, and particle thermophoresis in the limit of vanishing particle inertial effects is quantitatively modeled for applications in gas turbines.
Abstract: The interaction between turbulent diffusion, Brownian diffusion, and particle thermophoresis in the limit of vanishing particle inertial effects is quantitatively modeled for applications in gas turbines. The model is initiated with consideration of the particle phase mass conservation equation for a two-dimensional boundary layer, including the thermophoretic flux term directed toward the cold wall. A formalism of a turbulent flow near a flat plate in a heat transfer problem is adopted, and variable property effects are neglected. Attention is given to the limit of very large Schmidt numbers and the particle concentration depletion outside of the Brownian sublayer. It is concluded that, in the parameter range of interest, thermophoresis augments the high Schmidt number mass-transfer coefficient by a factor equal to the product of the outer sink and the thermophoretic suction.
31 citations
TL;DR: In this paper, a nonlinear analysis was performed to examine fully the mechanism of turbulent mass transfer to a solid surface, and it was found that at high Schmidt numbers the Reynolds transport is controlled by fluctuations of much lower frequency than the most energetic velocity fluctuations.
Abstract: A linear form of the mass balance equation is used to determine how turbulent transport of mass to a solid wall is related to the fluctuating velocity field. It is found that at high Schmidt numbers the Reynolds transport is controlled by fluctuations of much lower frequency than the most energetic velocity fluctuations. The characteristic of the velocity field that emerges as being most important is the small frequency limiting value of the spectral function of the velocity fluctuations normal to the wall. However, the linear theory that is explored does not predict the correct dependency of the average and the mean-squared deviation of the mass transfer coefficient on Schmidt number. A nonlinear analysis must be performed to examine fully the mechanism of turbulent mass transfer to a solid surface.
27 citations
TL;DR: In this article, the authors considered the nonlinear double-diffusive convection in a Boussinesq fluid with stable constant vertical solute gradient, and bound by two differentially heated rigid inclined parallel plates.
Abstract: The nonlinear double-diffusive convection in a Boussinesq fluid with stable constant vertical solute gradient, and bound by two differentially heated rigid inclined parallel plates is considered. The analysis was carried out by a Galerkin method for the cases when the angle of inclination was 0°, −45° and +45° (positive angle denotes heating from below, and negative angle denotes heating from above). The counter-rotating cells predicted by the linear theory merge into single cells with the same sense of rotation within a very short period of time even under slightly supercritical conditions. This is consistent with the experimental observations. Furthermore, as observed in the experiments, the evolution of instability is more rapid when heating is from above than when heating is from below. Our results for a salt-heat system are in excellent agreement with those based on the limiting case of Lewis number → 0 and Schmidt number → ∞.
25 citations
TL;DR: In this article, the Czochralski growth system in the limits Sc, R → ∞, σ → 0, Δ → 0 is considered, where Sc is the Schmidt number, R is the Reynolds number of the liquid phase, Δ the Prandtl number, and Δ the ratio of the solution diffusivities in the liquid and solid phases.
14 citations
TL;DR: In this paper, a new theoretical expression for turbulent heat and mass transport in inelastic non-Newtonian liquids has been proposed under the assumption that the Schmidt number is fairly high.
9 citations
TL;DR: In this article, a semi-permeable membrane forms part of a vertical plane boundary which separates pure solvent from a solution of bulk concentration, and the boundary layer is analyzed on the assumption that there is no stirring in the bulk solution so the only motion is the natural convection driven by the relative buoyancy of the solute-poor fluid near the membrane.
Abstract: A semi-permeable membrane forms part of a vertical plane boundary which separates pure solvent from a solution of bulk concentration $C_b $. The osmotic flux J is given by $J = P\Delta C$ where P is the osmotic permeability of the membrane and $\Delta C$ is the concentration difference across it, less than $C_b $ because the osmotic flow tends to sweep solute away from the membrane and a boundary layer is set up. This boundary layer is analysed on the assumption that there is no stirring in the bulk solution so the only motion is the natural convection driven by the relative buoyancy of the solute-poor fluid near the membrane. The flow and concentration distribution are taken to be steady and two-dimensional. The key dimensionless longitudinal coordinate is $x = P^4 C_b^3 \sigma X/g'D^2 $, where X is distance from the leading edge of the membrane, $g'$ is the buoyancy force per unit mass and concentration difference, and $D,\sigma ( \sigma \gg 1 )$ are the solute diffusivity and Schmidt number of the flui...
3 citations
TL;DR: In this article, the average mass transfer coefficient between a solution flowing through a pipe and a square plate immersed in the flow is determined as a function of the velocity of the flow and its physical characteristics.
3 citations
01 Jan 1982
TL;DR: In this paper, the authors calculated the fluctuating concentration field from the mass balance equation using measured values of the fluctuated velocity field and found that the concentration boundary layer acts as a filter in that only velocity fluctuations of much lower frequency than the most energetic velocity fluctuations are effective in transporting mass at large Schmidt numbers.
Abstract: The fluctuating concentration field is calculated from the mass balance equation using measured values of the fluctuating velocity field. It is found that the concentration boundary-layer acts as a filter in that only velocity fluctuations of much lower frequency than the most energetic velocity fluctuations are effective in transporting mass at large Schmidt numbers. Two parameters characterizing the velocity field emerge as being quite important. These are the limiting behavior of the spectral density function of the normal velocity fluctuations for frequency approaching zero and a scale characterizing the spanwise mixing.
01 Jan 1982