COVID-19, caused by the SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) virus, has been rapidly spreading worldwide since December 2019, causing a public health crisis. Recent studies showed SARS-CoV-2's ability to infect humans via airborne routes. These motivated the study of aerosol and airborne droplet transmission in a variety of settings. This study performs a large-scale numerical simulation of a real-world dentistry clinic that contains aerosol-generating procedures. The simulation tracks the dispersion of evaporating droplets emitted during ultrasonic dental scaling procedures. The simulation considers 25 patient treatment cubicles in an open plan dentistry clinic. The droplets are modeled as having a volatile (evaporating) and nonvolatile fraction composed of virions, saliva, and impurities from the irrigant water supply. The simulated clinic's boundary and flow conditions are validated against experimental measurements of the real clinic. The results evaluate the behavior of large droplets and aerosols. We investigate droplet residence time and travel distance for different droplet diameters, surface contamination due to droplet settling and deposition, airborne aerosol mass concentration, and the quantity of droplets that escape through ventilation. The simulation results raise concerns due to the aerosols' long residence times (averaging up to 7.31 min) and travel distances (averaging up to 24.45 m) that exceed social distancing guidelines. Finally, the results show that contamination extends beyond the immediate patient treatment areas, requiring additional surface disinfection in the clinic. The results presented in this research may be used to establish safer dental clinic operating procedures, especially if paired with future supplementary material concerning the aerosol viral load generated by ultrasonic scaling and the viral load thresholds required to infect humans.

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A numerical modeling of electrification and ion transport in ionic conductor liquids (oils) is conducted while allowing for the Frumkin-Butler-Volmer kinetics responsible for the ion transfer at metal electrode surfaces. The numerically predicted near-electrode polarized layer is validated against a boundary layer analytical solution for low voltages also developed in this paper. Another benchmark related to microchannels with dielectric walls with a non-zero ζ-potential is used to validate the implementation of the Coulombic body force responsible for the electro-osmotic flow. Finally, the case of an electrohydrodynamic flow in a microchannel (a model for the flow and charging inside an electrostatic atomizer) with two metal electrodes of opposite polarity attached is considered aiming at the prediction of the resulting net charge at the channel exit. The charging electrodes occupy only a fraction of the channel walls, which are otherwise insulated. It is shown that the considered channel length does not play a role in determining the available net charge achieved at the exit. Indeed, the value of the spray current practically does not vary along the exit section of the channel (behind the electrode part), which means that irrespective of the exit location, the spray current would be the same. Moreover, it is shown that in the present case, the role of the Smoluchowski slip near the electrodes is negligibly small compared to the viscous scraping of the polarized layer under any realistic values of the imposed longitudinal electric field.