A numerical modelling investigation of the development of a human cough jet

Abstract

PurposeThis study aims (1) to numerically investigate the characteristics of a human cough jet in a quiescent environment, such as the variation with time of the velocity field, streamwise jet penetration and maximum jet width. Two different turbulence modelling approaches, the unsteady Reynolds-averaged Navier–Stokes (URANS) and large eddy simulation (LES), are used for comparison purposes. (2) To validate the numerical results with the experimental data.Design/methodology/approachTwo different approaches, the URANS and LES, are used to simulate a human cough jet flow. The numerical results for the velocity magnitude contours and the spatial average of the two-dimensional velocity magnitude over the corresponding particle image velocimetry (PIV) field of view are compared with the relevant PIV measurements. Similarly, the numerical results for the streamwise velocity component at the hot-wire probe location are compared with the hot-wire anemometry (HWA) measurements. Furthermore, the numerical results for the streamwise jet penetration are compared with the data from the previous experimental work.FindingsBased on the comparison with the URANS approach and the experimental data, the LES approach can predict the temporal development of a human cough jet reasonably well. In addition, the maximum width of the cough jet is found to grow practically linearly with time in the far-field, interrupted-jet stage, while the corresponding axial distance from the mouth of the jet front increases with time in an approximately quadratic manner.Originality/valueCurrently, no numerical study of human cough flow has been conducted using the LES approach due to the following challenges: (1) the computational cost is much higher than that of the URANS approach; (2) it is difficult to specify the turbulent fluctuations at the mouth for the cough jet properly; (3) it is necessary to define the appropriate conditions for the droplets to obtain statistically valid results. Therefore, this work fills this research gap.

Prediction of respiratory droplets evolution for safer academic facilities planning amid COVID-19 and future pandemics: A numerical approach

“…No significant difference was found in accuracy between the URANS and the LES model predicting the streamwise penetration of a coughing jet flow in an indoor environment. Even though URANS model cannot capture the different scales of the turbulent flow like other advanced numerical models [ [26] , [27] , [28] , 53 ], the low computational cost of the URANS model made this captivating for designing technologies to prevent the spread of airborne diseases and preserve the world economy. The practical application of the URANS model was demonstrated in the design of a disinfection robot amid the COVID-19 and future pandemics [ 35 ].…”

“…To validate the airflow or continuous phase modeling, we compare the maximum streamwise penetration distance ( X p ), which is the variation of the longest flow distance along the streamwise direction, as a function of time for the cough and sneeze flow obtained in the unsteady RANS (URANS) simulations with experiments developed by Wei and Li [ 30 ] and Large Eddy Simulations (LES) performed by Bi et al [ 26 , 27 ]. Wei and Li [ 30 ] estimated the maximum streamwise penetration distance of a real cough in two stages.…”

“…Moreover, the evaporation and transport of droplets larger than 100 μ m are not affected by the airflow pattern in the vapor plume since the velocity of the droplets is larger than the vapor plume expansion velocity [ 22 ]. Numerical simulations with more advanced methods such as large-eddy simulations (LES) and direct numerical simulations (DNS), which accurately capture the characteristics of turbulent jet flows, have become one of the most popular ways to assess the dispersion of coughing droplets in indoor environments [ 26 , 27 ]. studied the characteristics of a human cough jet development in a quiescent indoor environment using LES simulations.…”

“…Second, as introduced previously, LES and DNS are the most advanced methods for cough/sneeze flow simulations. These methods can improve the accuracy of turbulent cough/sneeze puff prediction in indoor environments [ 27 , 28 , [31] , [32] , [33] , [34] ]. However, the significantly refined grid and time-dependent algorithm in turbulence resolution make it too expensive in terms of computational cost, especially for many practical applications such as complex scenarios with multiple infectious sources in a room and external conditions.…”

A review on indoor airborne transmission of COVID-19– modelling and mitigation approaches

“…Bi et al [ 126 ] simulated the human cough jet development in the indoor environment using LES. They argued that the LES simulations are able to monitor the temporal behavior of a human cough jet very accurately when compared to unsteady URANS methods based on experimental data.…”