  Violent expiratory events, such as coughing and sneezing, are highly
nontrivial examples of a two-phase mixture of liquid droplets dispersed into an
unsteady turbulent airflow. Understanding the physical mechanisms determining
the dispersion and evaporation process of respiratory droplets has recently
become a priority given the global emergency caused by the SARS-CoV-2
infection. By means of high-resolution direct numerical simulations (DNS) of
the expiratory airflow and a comprehensive Lagrangian model for the droplet
dynamics, we identify the key role of turbulence on the fate of exhaled
droplets. Due to the considerable spread in the initial droplet size, we show
that the droplet evaporation time is controlled by the combined effect of
turbulence and droplet inertia. This mechanism is clearly highlighted when
comparing the DNS results with those obtained using coarse-grained descriptions
that are employed in the majority of the current state-of-the-art
investigations, resulting in errors up to $100\%$ when the turbulent
fluctuations are filtered or completely averaged out.
