Experimental measurements of airflow features and velocity distribution exhaled from sneeze and speech using particle image velocimetry

Abstract

Airflow exhaled from sneeze and speech is an important source of viruses and droplets in daily life and may cause imperceptible virus propagation. The velocities of sneeze and speech airflow exhaled from 10 healthy young participants repeatedly using high-frequency (2986 Hz) particle image velocimetry are measured. The parameters for describing the dynamic process of sneeze airflow, such as sneeze duration time (SDT), peak velocity time (PVT), maximum velocities, and sneeze spread angle, are analyzed. The sneeze airflow lasts 430 ms (SDT) and reaches the peak velocity in the first 20 ms (PVT). The maximum sneeze airflow velocity is approximately 15.9 m/s. The temporal variation of the sneeze velocity exhibits the gamma distribution. For speech airflow, the maximum instantaneous velocity and maximum time-averaged velocity are reported. The maximum instantaneous velocity is approximately 6.25 m/s, whereas the time-averaged value is only 0.208 m/s owing to the extremely small airflow velocity among syllables. The vertical/horizontal spread angles of the airflow are 15.1°/15.4° for sneeze and 52.9°/42.9° for speech. The difference in airflow features based on gender is generally slight for both sneeze and speech. Subsequently, an ensemble-average operation is conducted to obtain the general and representative velocity distributions. We report each component of the temporal and spatial velocity distributions of the sneeze airflow and the time-averaged velocity distribution of the speech airflow. These detailed distribution data can provide a comprehensive understanding of sneeze and speech airflow movement mechanisms as well as a detailed database for future sneeze and speech computational fluid dynamics simulations.

Keywords: Particle image velocimetry; Sneeze; Speech; Spread angle; Time-averaged velocity; Velocity profile.

Fig. 1

Schematic illustration of chamber and setups for vertical/horizontal measurements.

Fig. 2

Temporal variation of maximum velocity at $x/L_0=2.5$ of one sneeze case, and definitions of PV, PVT, and SDT based on it.

Fig. 3

Temporal variations of dimensionless maximum velocity of all cases at $x/L_0=2.5$ (upper) and ensemble-averaged value (lower).

Fig. 4

Vertical profiles of ensemble-averaged velocity variation with time at positions $x/L_0=1.0,2.0,and3.0$.

Fig. 5

Horizontal profiles of ensemble-averaged velocity variation with time at positions $x/L_0=1.0,2.0,and3.0$.

Fig. 6

Vertical (left) and horizontal (right) instantaneous distribution of ensemble-averaged velocity at times $t/PVT=\mathrm{1,3,6},and9$.

Fig. 7

Maximum velocity temporal variation at $x/L_0=2.5$ in 2 s for one speech case. Airflow and velocity varied for different syllables.

Fig. 8

Vertical and horizontal distribution of time-averaged velocity vectors of speech airflow.

Fig. 9

Vertical (left) and horizontal (right) profiles of ensemble-averaged results of time-averaged velocity components and their deviations. Vertical distribution vector comprises and , as well as their deviation from time-averaged and ; horizontal distribution vector comprises and , as well as their deviation from and .