Boris Krasovitov

In this study, we developed a model of convective heat and mass transfer of an acoustically levitated slurry droplet that evaporates in an atmosphere of air, water vapor, and soluble gas. The advanced model considered the effects of acoustic streaming, forced convection, and non-isothermal gas absorption on the evaporation rate of a liquid droplet containing small solid particles. It is shown that the time of porous shell formation decreases with the increase of sound pressure level (SPL) and increases with the increase in frequency. Adding soluble gas to the gaseous phase shortens the time required for porous shell formation during slurry droplet drying. As shown by numerical calculations, in a gas mixture containing air with an ammonia content of 30%, at a temperature of 293 K and a humidity of 50%, with an acoustic field frequency of 2π·45 kHz and an SPL of 140 dB, the time of porous shell formation of a silica-water slurry droplet with the initial radius of 250 µm is about half shorter than that in a gas mixture not containing an active gas. The prediction of the developed model was in good agreement with the experimental results available in literature.

We suggest a two-dimensional model of adsorption of trace atmospheric gases by mineral dust particles with origin from desert soils. The model is based on the application of theory of turbulent diffusion in the atmospheric boundary layer (ABL) in conjunction with the model of gas adsorption by porous solid particles. The numerical model is formulated using parameterizations based on aeolian (by wind) dust emission experiments. The aeolian field experiments were performed at a dust source (loess soil in Northern Negev, Israel) using a portable boundary layer wind tunnel to determine the emitted particulate matter (PM) fluxes for different wind speeds and varying soil conditions. The numerical analysis is performed for the adsorption of gas-phase HNO₃ by dust particulate matter. We determined numerically concentration distributions of the atmospheric dust particulate matter, and trace gas using shear velocity and emitted dust flux from the soils employed in the experiments. Analysis was performed for the case of neutral and slightly stable stratification of ABL typical for dust storm events in the East Mediterranean. The numerical analysis showed that during dust events the slightly stable atmosphere is characterized by higher concentration of PM₁₀ in the surface layer than the neutrally stable atmosphere. It is found that in the case of neutral stratification as well as for stable atmospheric stratification the concentration of nitric acid HNO₃ strongly depends on concentration of atmospheric dust particles. The developed model enhances our capacity of quantification of atmospheric dust effects in climate models as well as health risk assessment.