Simulating Gas-Liquid Interactions

Dynamic QM/MM A Hybrid Approach to Simulating Gas-Liquid Interactions... 

Prediction of gas solid flow fields, in processes such as pneumatic transport lines, risers, fluidised-bed reactors, hoppers and precipitators are crucial to the operation of most process plants. Up to now, the inability to accurately model these interactions has limited the role that simulation could play in improving operations. In recent years, CFD software developers have focused on this area to develop new modelling methods that can simulate gas-liquid-solid flows to a much higher level of reliability. As a result, process industry... 

Yang N, Wu Z, Chen J, et al Multi-scale analysis of gas-liquid interaction and CFD simulation of gas-liquid flow in bubble columns, Chem Eng Sd 66(14) 3212-3222, 2011. 

A second case to be considered is that of mixtures witli a small size ratio, <0.2. For a long time it was believed tliat such mixtures would not show any instability in tire fluid phase, but such an instability was predicted by Biben and Flansen [109]. This can be understood to be as a result of depletion interactions, exerted on the large spheres by tire small spheres (see section C2.6.4.3). Experimentally, such mixtures were indeed found to display an instability [110]. The gas-liquid transition does, however, seem to be metastable witli respect to tire fluid-crystal transition [111, 112]. This was confinned by computer simulations [113]. 

These values were obtained by fitting experimental Henry s law constants to the theoretical expression for potentials obtained by assuming that the gas-solid interaction energy is given by a pairwise sum over the carbon atoms of Lennard-Jones (LJ) inverse 12-6 functions of separation distance [45]. From fits of experimental liquid state data to simulations of the LJ liquid [46]. 

Understanding the transport and fate of pollutants in soils is among the most challenging and demanding current research topics. Predictions of mobility and transport of chemicals in the natural compartments usually rely on models and mathematical simulations. The effectiveness of these hinges on a fundamental knowledge of the reactions and interactions of the pollutant substrate at the boundaries of the respective compartments, governing its behavior in the different phases (gas, liquid, and solid). Phenomena have to be identified, characterized, and quantified with respect to kinetics and thermodynamics to provide a comprehensive and predictive model of the natural system under consideration. 

These trends are similar to what is observed in simpler model fluids with purely spherically s3mimotric interactions [298, 313], which is to some extent expected because the gas liquid transition in Stockmayer fluids is mainly driven by the isotropic LJ (12,6) interactions underlying this model. We show in Ref. 307 that the main effects of HS matrices on the condensation can be reproduced when the dipolar model fluid is approximated by a fluid with angle-averaged dipolar interactions that are not only spherically symmetric but also short-ranged (they decay in proportion to for r — cx)). This notion is particularly important for future simulation studies on adsorbed dipolar fluids. 

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