Numerical evaluation of the particle pollutant homogeneity and mixing time in a ventilated room

With the increase of the computational capability, three-dimensional Lagrangian simulation can now be applied to evaluate the particle pollution evolution in ventilated rooms. The present study deals with the evaluation of 5.0 μm particle dispersion in a prototypical-ventilated room of 10 m3. Two ventilation slots and three different airflow rates have been simulated. Particle trajectories have been calculated using a Lagrangian model. Dispersion of particles has been analyzed for the case of an external pollutant source, a homogeneous particle injection within the room and some puff releases in different locations. Discussion about the best procedure to get useful information about the particle cloud is then presented and illustrated from the simulation results. The definition of two indices based on geometrical and statistical parameters are proposed in order to correctly evaluate the particle cloud homogeneity and mixing time.