Rayleigh–Taylor unstable condensing liquid layers with nonlinear effects of interfacial convection and diffusion of vapour

Literature has indicated that, experimentally, solvent fronts in hybrid thermal solvent recovery processes progress more rapidly than what can be predicted using current approximations and more rapidly than thermal processes alone [1]. The equations that govern thermal multiphase flow through porous media are extremely complex and it is very difficult to decouple the contribution of the mass transfer mechanisms from the thermal effects. This paper explores the behavior of the mass transfer mechanisms in these processes through an examination of the nonlinear one-dimensional advection diffusion/dispersion (ADD) equation using finite difference methods. Earlier work [2] indicated that the linear ADD equation, using physically estimated parameters for diffusion and dispersion coefficients obtained from the literature, could not account for the solvent front progression rate predicted by Edmunds [3]. The results in this preliminary study indicate that the nonlinear effects are important in predicting the progression of a solvent front using the one dimensional ADD equation. The shapes and rate of propagation of the concentration profiles are influenced by both velocity and diffusion functionality. These results are more consistent with the solvent front propagation rate predicted by Edmunds [3]. These results also suggest that including nonlinear effects in traditional reservoir simulation software may be necessary in the modeling of solvent processes. Further work is needed to explore and understand the influence of the velocity and diffusion functionality necessary to mimic the behaviour observed in thermal solvent recovery processes and to further increase the understanding of their impact on solvent front propagation.

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Study of a Possibility of Deep Laser Cooling of Magnesium Atoms for Designing the New-Generation Frequency Standard

Siberian Journal of Physics ◽

10.54362/1818-7919-2012-7-4-6-18 ◽

2012 ◽

Vol 7 (4) ◽

pp. 6-18

Author(s):

Denis Brazhnikov ◽

Anatoliy Bonert ◽

Andrey Goncharov ◽

Alexey Taichenachev ◽

Anatoliy Tumaikin ◽

...

Keyword(s):

Laser Cooling ◽

Strong Field ◽

Nonlinear Effects ◽

Frequency Standard ◽

Frequency Detuning ◽

Distribution Profile ◽

Light Waves ◽

Fokker Plank Equation ◽

New Generation ◽

And Diffusion

Theoretical analysis of sub-Doppler laser cooling of 24Mg atoms using 33 P2 → 33 D3 transition in the field of two counterpropagating light waves with opposite circular polarizations is presented. The standard semi-classical approach based on the Fokker-Plank equation is exploited for numerical modeling of laser cooling. The problem is solved out of limits of slow atom approximation and for arbitrary light intensity. The dependences of light force and diffusion on an atomic velocity are studied for various frequency detuning and Rabi frequency. Also, to obtain optimal parameters of laser cooling, the atomic velocity distributions are investigated for various conditions and the dependence of average atomic kinetic energy on the light field intensity and frequency detuning is calculated. In the case of strong field a multi-spike velocity distribution profile is observed. It results from various nonlinear effects accompany absorption of laser photons by atoms. In conclusion we make additional recommendations to increase atoms in metastable state 33 P2, what is necessary for effective laser cooling

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Nonlinear effects in the process of propagation of internal waves with regard for the turbulent viscosity and diffusion

Physical Oceanography ◽

10.1007/s11110-010-9053-7 ◽

2009 ◽

Vol 19 (5) ◽

pp. 267-288

Author(s):

A. A. Slepyshev ◽

I. S. Martynova

Keyword(s):

Internal Waves ◽

Turbulent Viscosity ◽

Nonlinear Effects ◽

And Diffusion

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Meridional Circulation, Turbulence, and Diffusion Processes in Stars

International Astronomical Union Colloquium ◽

10.1017/s0252921100080477 ◽

1976 ◽

Vol 32 ◽

pp. 109-116 ◽

Cited By ~ 1

Author(s):

S. Vauclair

Keyword(s):

Convection Zone ◽

Diffusion Processes ◽

Meridional Circulation ◽

Diffusion Time ◽

Work In Progress ◽

First Results ◽

Stellar Envelopes ◽

And Diffusion ◽

Turbulence And Diffusion ◽

Hr Diagram

This paper gives the first results of a work in progress, in collaboration with G. Michaud and G. Vauclair. It is a first attempt to compute the effects of meridional circulation and turbulence on diffusion processes in stellar envelopes. Computations have been made for a 2 Mʘstar, which lies in the Am - δ Scuti region of the HR diagram.Let us recall that in Am stars diffusion cannot occur between the two outer convection zones, contrary to what was assumed by Watson (1970, 1971) and Smith (1971), since they are linked by overshooting (Latour, 1972; Toomre et al., 1975). But diffusion may occur at the bottom of the second convection zone. According to Vauclair et al. (1974), the second convection zone, due to He II ionization, disappears after a time equal to the helium diffusion time, and then diffusion may happen at the bottom of the first convection zone, so that the arguments by Watson and Smith are preserved.

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