AeroSolved: Wall boundary conditions for liquid multispecies aerosol deposition at transient and high-humidity flows

Conducting computational simulations of multispecies aerosols poses considerable challenges, predominantly due to the intricate confluence of multiphysical properties and diverse scales characteristics to aerosol processes. Arising modeling complexities require the use of various co-existing submodels and substantial computational resources for the resolution of the required scales. AeroSolved was introduced and developed to overcome some of these constraints, facilitating simulations of multispecies evolving aerosols in the drift-flux mixture model formulation with large particle number densities by taking advantage of the Eulerian framework. Here, we analyze and assess the underlying models by applying appropriate boundary conditions for accurate predictions of aerosol deposition, including gas phase absorption. Particular attention is given to the modeling of inhalation flows in which the gas–liquid mass transfer between the phases is taken into account, together with increased water condensation due to high humidity conditions present in the airways. The condensation or evaporation of gas species at the wall is represented via the application of Raoult’s law, including activity coefficients corrections for non-ideal mixture behavior. A set of boundary conditions with increasing levels of complexity are presented, starting from the deposition of non-evolving dry particles to liquid multispecies particles in the presence of water-saturated wet walls. Drift-flux model formulation requires particular attention to the common use of no-slip boundary conditions for aerosol particles. The verification cases delineate boundary conditions and deliver benchmark data for further validation despite the limited availability of existing experimental data for such aerosol flow conditions. Finally, the developed boundary conditions are applied to a transient aerosol inhalation flow scenario in the geometry of a bent pipe with wet walls, mimicking a simplified upper respiratory tract shape. Such geometrically simplified configuration allows for an exhaustive examination of simulations sensitivities and achievable numerical accuracy for applied various computational mesh densities. Developed boundary conditions, together with delivered numerical studies including examples of their application with obtained computational mesh-independent predictions for the aerosol deposition, can be readily applied in more complex geometry scenarios, including realistic human upper respiratory cast models, and serve aerosol dosimetry purposes.