Modeling Coagulation, Transport and Deposition of a Nanoparticle Aerosol by a Moment Method

It is well known that the particle size distribution of an aerosol of nanoparticles can quickly change by self-coagulation, transport and wall deposition. Although these physical phenomena are important for industrial applications, they also induce particular consequences in terms of occupational hygiene when a potentially hazardous nano-structured aerosol is considered. In this framework, modeling nano-aerosol dynamics is needed in order to evaluate and characterize occupational exposures. One of the most efficient ways of modeling the evolution of the particle size distribution consists in using the moment method including a coagulation source term. The quadrature method of moments based on numerical backward differentiation was found efficient (Guichard et al., 2011) for solving the system of differential-algebraic equations obtained to treat coagulation. This earlier study also highlighted the need for taking into account the fractal parameters of nanoparticle aggregates, the shape of aggregates significantly influencing the Brownian and turbulent coagulation kinetics. We propose now a complete model that allows tracking both the temporal and the spatial evolution of an aerosol of nanoparticles. The deposition is taken into account by means of a moment transformation of the dynamic boundary layer model (Nerisson et al., 2011), which leads to a good computational performance and to numerical results that are in good agreement with experimental measurements. The implementation of this complete Eulerian model in computational fluid dynamics will be then assessed for simple cases (pipe flow and ventilated room) by comparison with both analytical solutions and experimental results.