Showing papers on "Schmidt number published in 1976"

Mathematical Models of Turbulent Flames; A Review

Abstract: The problem of predicting turbulent flame phenomena is reviewed, with special reference to the turbulent diffusion flame and to the confined pre-mixed flame downstream of a flame-holder. Attention is given to means of describing instantaneous and time-average states, and to the distinctions between the micro-scale aspects of the two flame types which these permit. A model for micro-scale reduction is proposed; and this is employed to derive the influence of the Schmidt number on burning rates in diffusion flames, and the influence of laminar flame speed on burning rates in confined pre-mixed flames. Both influences are weak. It is shown that the mixing-length version of the eddy-break-up model is likely to be closer to the truth than the model employing the local dissipation rate of turbulence energy.

Effects of mass transfer on free convective flow of a dissipative, incompressible fluid past an infinite vertical porous plate with suction

Abstract: An analysis of the mass transfer effects on the free convective flow of an incompressible, dissipative, viscous fluid past an infinite, vertical porous plate with constant suction, has been carried out. Approximate solutions to coupled non-linear equations governing the flow are derived. The velocity and the temperature profiles are shown graphically for air (P=0·71). The effects of Gr (Grashof number), Gc (the modified Grashof number), Sc (Schmidt number), E (Eckert number) are discussed qualitatively during the course of discussion. It is observed that due to the addition of the foreign mass, there is a rise in the velocity and a fall in the temperature. But the skin-friction increases when Sc≶1 and it decreases when Sc ∼1. The rate of heat transfer increases for Sc 1.

Surface reaction with combined forced and free convection

Abstract: The influence of combined forced and free convection on the surface reaction of a laminarly flowing species in a rectangular channel is studied. The free convective motion, which is superimposed upon the main axial flow, arises from a transverse density gradient produced by the release of a reaction product, or heat, at the channel wall. A numerical stream function-vorticity method is employed to solve the three-dimensional conservation equations in the case of large Schmidt number. Effects of aspect ratio, diffusivity ratio, surface reaction rate, and Rayleigh number upon the overall reactant conversion rate and local Sherwood number are examined. Reasonable agreement is obtained with experimental data for a hydrochloric acid-calcium carbonate surface reaction.

Effect of the size of particles or drops on the diffusion of an impurity in a turbulent jet

Abstract: Under the assumption that the. velocity of the particles entering into a mole at the start of its “life∝ differs from zero, an analog of the Schmidt number is determined with the turbulent flow of a mixture of a gas and solid particles. In accordance with the formula obtained, in the limiting case, where the particle size tends toward zero, the Schmidt number for a mixture of a gas and solid particles tends toward the Schmidt number for the gas. A model is proposed for determining the initial velocity of the particles in a mole. The results of a calculation of this velocity and of the analog of the Schmidt number, made using the proposed model, are in satisfactory agreement, respectively, with the values of the initial velocity, obtained indirectly from experiment, and with the mean Schmidt number for particles of small and medium sizes.