Numerical simulations of the flow and aerosol dispersion in a violent expiratory event: Outcomes of the “2022 International Computational Fluid Dynamics Challenge on violent expiratory events”

Abstract

This paper presents and discusses the results of the "2022 International Computational Fluid Dynamics Challenge on violent expiratory events" aimed at assessing the ability of different computational codes and turbulence models to reproduce the flow generated by a rapid prototypical exhalation and the dispersion of the aerosol cloud it produces. Given a common flow configuration, a total of seven research teams from different countries have performed a total of eleven numerical simulations of the flow dispersion by solving the Unsteady Reynolds Averaged Navier-Stokes (URANS) or using the Large-Eddy Simulations (LES) or hybrid (URANS-LES) techniques. The results of each team have been compared with each other and assessed against a Direct Numerical Simulation (DNS) of the exact same flow. The DNS results are used as reference solution to determine the deviation of each modeling approach. The dispersion of both evaporative and non-evaporative particle clouds has been considered in twelve simulations using URANS and LES. Most of the models predict reasonably well the shape and the horizontal and vertical ranges of the buoyant thermal cloud generated by the warm exhalation into an initially quiescent colder ambient. However, the vertical turbulent mixing is generally underpredicted, especially by the URANS-based simulations, independently of the specific turbulence model used (and only to a lesser extent by LES). In comparison to DNS, both approaches are found to overpredict the horizontal range covered by the small particle cloud that tends to remain afloat within the thermal cloud well after the flow injection has ceased.

Particle dispersion produced by a turbulent free convection flow in a room-sized cubical cavity

“…These pathogen-laden aerosols may be expelled by an infected person when sneezing, coughing, talking or singing. The short-term, short-range dispersion of the flow and aerosol clouds has been considered in the past successful "2022 International Computational Fluid Dynamics Challenge on violent expiratory events" [2]. The objective of this Challenge was to determine the ability of Unsteady Reynolds Averaged Navier-Stokes (URANS) and Large-Eddy Simulation (LES) techniques to simulate the flow and the evaporative aerosol cloud dispersion generated just after the end of an isolated cough ejecting warm fluid into a quiescent colder ambient.…”