Numerical analysis of capillarity in packed spheres: planar hexagonal-packed spheres

General solutions of the capillary pressure for liquids as a function of contact angle and volume in planar close-packed spheres have been calculated numerically using Surface Evolver software. Applied pressure differences between liquid and vapor result in undulating (puckered) menisci exhibiting anticlastic curvature in the narrower spaces near particle contacts. The corresponding capillary pressures exhibit maxima with infiltration volume (minima with drainage), corresponding to critical pressures for engulfment of the spheres by the liquid (vapor). The analysis also reveals the formation of residual pendular rings of the wetting phase around particle contacts. Pendular ring formation is explored further by analyzing hexagonally packed spheres separated by 1/10 their radius. The results are discussed relative to the wide range of approximate solutions available in the literature.     

v---v pumping in H2: estimate of induced dissociation at 300°K

By means of the stimulated Raman effect one may produce in H₂, D₂, and in several other gases, a substantial population in the ν = 1 state. Subsequent to the pulse excitation v---v energy transfers rapidly generate a vibrational distribution which is approximately equivalent to (3–4) × 10³°K. Then, in H₂ + D₂ mixtures metathetic reactions occur. Here we report on a computer simulation of an experiment described elsewhere, designed to estimate whether a measurable fraction of the hydrogen molecules reach the upper vibrational level and dissociate. Solutions of the coupled differential equations show that the anticipated hydrogen atom concentrations are too low by a factor of 10⁷-10⁸ to account for the observed H/D exchanges. These calculations also show that the conventional phenomenological rate equation for dissociation does not apply to this highly non-thermal distribution.     

Ein Randwertproblem aus der Bodenmechanik

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